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En´gine   Pronunciation: en´jin 

n.  A compound machine by which any physical power is applied to produce a given physical effect.

How to Turn Off and On Animated Images


What is an Engine

How an Engine Works

The Four Stroke Combustion Cycle
(The Otto Cycle)


Types of Engines
In-line engines     V-Type Engines     Flat (Horizontal-Opposed) Engines     Rotary Engine
Overhead Camshaft (OHC)     Double Overhead Camshaft (DOHC)     Overhead Valve (OHV)
Multivalve Engines

Engine Components
Pistons     The Valve Train     Connecting Rod     Connecting Rod Bearings     Crankshaft     Flywheel    
Main Bearings     The Cylinder Head     Displacement    
Intake     Compression     Power     Exhaust
Combustion Chamber     Piston rings     Wrist Pin     Timing Chain/belt     Spark plug     Gaskets
The Engine's Lubrication System     Push Rods     Serpentine Belts     Engine Cooling     Harmonic Balancer
Engine Balance
Engine Problem Solver
Check your Engine Condition on a Regular Basis
What's Needed to Keep the Engine in Good Condition?

Charles and Frank Duryea designed and built the car together, showing off their invention on the streets of Springfield, Massachusetts, on September 22, 1893.
See more Automobile History here

 Under the hoods of our cars can be a mysterious, confusing jumble of metal, tubes and wires to the inexperienced.

They start when we turn the key in the ignition which triggers a complex sequence of events that gets our car moving and take us where we want to go.

First, the battery completes an electrical circuit, and that activates the electronic control unit, the fuel pump, and the fuel injectors. At the same time - next power flows from the battery to the starter, which cranks the engine. The starter turns the crankshaft, the driving force of the whole engine, and it is kept turning by the pistons, which are like the pedals on a bicycle.

All performed by the heart of the automobile,
the engine .
It converts fuel into the energy that powers the automobile.
 To operate, it requires clean air for the fuel, water for cooling, electricity (which it generates) for igniting the fuel, and oil for lubrication.
A battery and electric starter get it going.

What is an

An engine is a machine that converts energy into mechanical work.
An engine may get its energy from any of a number of sources, including fuels, steam, and air or water under pressure.

An external combustion engine is an engine which burns its fuel outside of the engine as a steam engine does.

An Internal Combustion Engine is any type of machine that obtains mechanical energy directly from the expenditure of the chemical energy of fuel burned in a combustion chamber that is an integral part of the engine.
Four principal types of internal-combustion engines are in general use:
 the Otto-cycle engine, the diesel engine, the rotary engine, and the gas turbine.

 The Otto-cycle engine, named after its inventor, the German technician Nicolaus Otto in 1876 , is the familiar gasoline engine used in automobiles today because it’s efficient, relatively inexpensive and easy to refuel. ;
the diesel engine, named after the French-born German engineer Rudolf Christian Karl Diesel, operates on a different principle and usually uses oil as a fuel. It is employed in electric-generating and marine-power plants, in trucks and buses, and in some automobiles.
Both Otto-cycle and diesel engines are manufactured in
two-stroke and four-stroke cycle models.

How an Engine Works

The purpose of a gasoline car engine is to convert gasoline into motion so that your car can move.

Currently the easiest way to create motion from gasoline is to burn the gasoline inside an engine.
 Therefore, a car engine is an internal combustion engine
- combustion takes place internally. 
(explosion inside!)

Containing the Explosion

Since the automobile engine is an "internal" combustion engine, a container must be found to keep the explosion on the inside,
this would be the combustion chamber,
which consists of a  Cylinder.

Think of it like this!
 Put the gasoline in a sturdy metal can and press down a tight-fitting lid. 
Find a way to introduce a lighted match inside that can, and bam! 
A contained explosion. 
Well, nearly contained. The lid will blow off.

So the engine isn't perfect just yet, but the "metal can" idea is an example of how an automobile cylinder works.
 Instead of a can with the lid sealing the opening from the outside,
the cylinder is a "can" constructed of thick and sturdy alloys, with the lid sealing the mouth of the cylinder from the inside, like the lid on a soup can.
That way, when the gasoline explodes 
(the spark plug provides the match-like spark),
 the lid moves straight up in the identical line of motion every time.

A good example would be an old war cannon,
where the soldiers load the cannon with gun powder and a cannon ball and light it.
That is internal combustion. 

Internal combustion gasoline engines run on a mixture of gasoline and air. The ideal mixture is 14.7 parts of air to one part of gasoline (by weight.)  Since gas weighs much more than air, we are talking about a whole lot of air and a tiny bit of gas. One part of gas that is completely vaporized into 14.7 parts of air can produce tremendous power when ignited inside an engine.

Two problems must be solved to make our engine work. 

First problem:
After the explosion, the exhaust must be siphoned off and a new supply of fuel must be introduced.
After all, one explosion won't propel a car very far. 

At the top of the cylinder is a pair of valves. 
(Okay, so many modern engines have tweaked this basic arrangement by adding additional valves, 
but the principle is still the same.)

The valve that lets the fuel in is called the "intake" valve. 
The one that lets out the exhaust,
 the by-product of the explosion, 
is called the "exhaust" valve.

A cylinder and its valves manipulate pressure in two ways that are no more sophisticated than what a small child at play might do.

Have you ever sucked on the end of a Coke bottle until all the air inside was gone and your lips were pulled into the opening?
All at once, a small leak developed and a tiny stream of air would rush in, making a squeaky noise and tickling your lips.

 What you did by drawing all the air out of the bottle was to create a vacuum. When the small leak around your lips inevitably developed, it wasn't the empty bottle drawing air back in, it was the normal pressure of the air around us (15 pounds per square inch) pushing its way back in.
And every child at some time discovers the joys of blowing up a balloon and releasing it with the end untied.

Did you ever leave a covered pot of cooking rice or spaghetti unattended? As the water heats up, gases or steam build and expand, creating pressure and eventually pushing the top off.
In cars there is a great deal more pressure, and only an airtight engine and cylinders can trap this pressure for its pushing abilities.

The compressed air forces its way out of the opening, the area of least resistance. Part of the genius of the four-stroke engine is its use of pressure and vacuum. Pressure and vacuum are keys to the success of the engine's four strokes: intake, compression, firing (power), and exhaust.

And the second problem,
a problem of a different sort:
 The explosion sends energy in a linear (related to a straight line) motion,
 but tires spin around. 
To restate the tire problem the way Henry Ford might have said it:
The reciprocating (up and down motion) energy produced by the gasoline explosion has to be converted into rotary (round and round motion) energy.

Within the cylinder, usually fixed, that is closed at one end and in which a close-fitting piston slides.

Pistons are the main factor in carrying out this task as they move
back and forth within the cylinder
(this is called reciprocating).

The in-and-out motion of the piston varies the volume of the chamber between the inner face of the piston and the closed end of the cylinder.

The outer face of the piston is attached to what is known as the crankshaft by a connecting rod.
All the pistons share this same crankshaft.

At the end of the crankshaft is a gear and on the other end a heavy flywheel with counterweights, which by their inertia minimize irregularity in the motion of the shaft.
That gear meshes with a gear on another shaft called a camshaft.
 On the camshaft and beneath each valve is a teardrop-shaped cam lobe.

 The piston turns (powers) the crankshaft with every firing stroke transforming the reciprocating motion of the piston into rotary motion.

In multicylindered engines the crankshaft has one offset portion, called a crankpin, for each connecting rod, so that the power from each cylinder is applied to the crankshaft at the appropriate point in its rotation.

 The crankshaft not only powers the car, it also powers the camshaft.
And the cam lobes, positioned above each valve, push the valves open each time the camshaft rotates and the cam lobe touches the valve stem.
The proper alignment of the gears keeps the engine firing to provide maximum power.

The fuel supply system of an internal-combustion engine consists of a tank, a fuel pump, and a device for vaporizing or atomizing the liquid fuel.
In Otto-cycle engines this device is either a carburetor or,
 more recently, 
a fuel-injection system.
In most engines with a carburetor, vaporized fuel is conveyed to the cylinders through a branched pipe called the intake manifold and, in many engines, a similar exhaust manifold is provided to carry off the gases produced by combustion. The fuel is admitted to each cylinder and the waste gases exhausted through mechanically operated poppet valves or sleeve valves. The valves are normally held closed by the pressure of springs and are opened at the proper time during the operating cycle by cams on a rotating camshaft that is geared to the crankshaft.

By the 1980s more sophisticated fuel-injection systems, also used in diesel engines, had largely replaced this traditional method of supplying the proper mix of air and fuel. In engines with fuel injection, a mechanically or electronically controlled monitoring system injects the appropriate amount of gas directly into the cylinder or intake valve at the appropriate time. The gas vaporizes as it enters the cylinder. This system is more fuel efficient than the carburetor and produces less pollution.

In all engines some means of igniting the fuel in the cylinder must be provided.
For example, the ignition system of Otto-cycle engines described below consists of a source of low-voltage, direct-current electricity that is connected to the primary of a transformer called an ignition coil.
The current is interrupted many times a second by an automatic switch called the timer. The pulsations of the current in the primary induce a pulsating, high-voltage current in the secondary. The high-voltage current is led to each cylinder in turn by a rotary switch called the distributor.
The actual ignition device is the spark plug, an insulated conductor set in the wall or top of each cylinder. At the inner end of the spark plug is a small gap between two wires. The high-voltage current arcs across this gap, yielding the spark that ignites the fuel mixture in the cylinder.

Because of the heat of combustion, all engines must be equipped with some type of cooling system. Some automobile engines are cooled by air. In this system the outside surfaces of the cylinder are shaped in a series of radiating fins with a large area of metal to radiate heat from the cylinder.
 Other engines are water-cooled and have their cylinders enclosed in an external water jacket.
In automobiles, water is circulated through the jacket by means of a water pump and cooled by passing through the finned coils of a radiator.

Unlike steam engines and turbines,
internal-combustion engines develop no torque when starting, and therefore provision must be made for turning the crankshaft so that the cycle of operation can begin. Automobile engines are normally started by means of an electric motor or starter that is geared to the crankshaft with a clutch that automatically disengages the motor after the engine has started.

The Four Stroke Combustion Cycle

Almost all cars currently use what is known as the four-stroke combustion cycle to convert gasoline into motion.
The four-stroke approach is also known as the Otto cycle,
in honor of Nicolaus Otto, who invented it in 1867.

To complete each cycle, a four-stroke reciprocating engine uses four movements of the piston, two toward the head (closed head) of the cylinder and two away from the head.

The four strokes are:
 Intake, Compression, Power and Exhaust.
The piston travels down on the Intake stroke, up on the Compression stroke,
down on the Power stroke and up on the Exhaust stroke.

How The Piston Works

The First Stroke:
The Intake Stroke

The first stroke of the cycle is the intake stroke. The crankshaft, located directly below the cylinders on some cars and below and between the cylinders on others, turns and begins to pull the piston down the length of the cylinder. We'll start with the piston at its highest point, referred to as top-dead-center. From this point the piston begins traveling down the cylinder, it forms a vacuum. The intake valve (see intake system) opens when the piston begins its downward movement, and air and fuel are drawn into the void.


The engine is designed to time the intake with the downward travel of the piston so that the whole time the piston moves downward, the air/fuel mixture is filling the vacuum in the cylinder. The intake valve shuts when the piston is at the bottom of the cylinder. This is called the intake stroke.

The Second Stroke:
The Compression Stroke

The crankshaft continues to spin, forcing the piston to rise, again through the  connecting rod, compressing the particles of gasoline and air now in the cylinder from the intake stroke. This compression of the air and fuel mixture will create a more forceful explosion. This is called the compression stroke. The compression stroke ends when the piston has returned to its position at the top of the cylinder.



The amount that the mixture is compressed is determined by the compression ratio of the engine.  The compression ratio on the average engine is in the range of 8:1  to 10:1.

This means that when the piston reaches the top of the cylinder, the air-fuel mixture is squeezed to about one tenth of its original volume.

The Third Stroke:
The Firing Stroke or The Power Stroke

At the finish of the compression stroke, a pulse of high voltage (see ignition system) is sent to the spark plug (located near the top of the cylinder), causing a spark to jump across the gap between the electrodes. This spark ignites the air-fuel mixture. The fuel explodes and the hot gases expand, forcing the piston down the cylinder (the path of least resistance). This turns the crankshaft and gives the car the power to move forward.

The timing of the combustion is such that the explosion of the air-fuel mixture


lasts for approximately the same amount of time that it takes for the piston to reach the bottom of its travel.

Each piston fires at a different time, determined by the engine firing order. By the time the crankshaft completes two revolutions, each cylinder in the engine will have gone through one power stroke.

The Fourth Stroke:
The Exhaust Stroke

Once the air-fuel mixture has burned, the byproducts of the combustion must be removed from the combustion chamber. This is handled during the exhaust stroke. As the rotating crankshaft again pushes the piston upward after the power stroke, the exhaust valve opens to allow the burned exhaust gas to be expelled to the exhaust system, allowing the piston to push the exhaust gasses out of the combustion chamber so that a fresh air-fuel mixture can be drawn in on the next intake stroke. The exhaust valve remains open until the piston again


reaches top-dead-center at which point it closes. The engine is now ready for the next intake stroke starting the four stroke process over again.

Since the cylinder contains so much pressure, when the valve opens, the gas is expelled with a violent force -
that is why a vehicle without a muffler sounds so loud.

This cycle is repeated over and over again as the engine runs.

Since most cars have 4, 6, or 8 cylinders, each cylinder will go through these same 4 cycles.
Normally, each cylinder is timed such that there is equal crankshaft rotation between the power strokes of each cylinder, allowing a smoother operating engine.

Here's the whole description in simple terms
The lid of the can is the piston, the container itself is the engine block, and the hole into which the piston fits is the cylinder. And the energy generated by the explosion must be converted over and over from the reciprocating motion of the piston into the rotary motion of the crankshaft.

This is pretty much the same motion you use to pedal a bike:

 Your knee goes up and down while your foot pedals 'round and 'round.

The rotating crankshaft of the engine transfers the linear motion of all of an engine's pistons into a circular motion,
 but that motion must be transferred from the engine to the wheels of the car.
This is dealt within the drive train.

The drivetrain is comprised of the transmission, differential, and various axle and drive shafts, each of which has its own specific purpose.
 Each is a vital link in getting rotational energy from the car's engine to its wheels.
 If any of these fails or is omitted, the car simply would not move. 

Explore The Drivetrain

How the internal combustion engine uses that energy
to make the wheels turn. 

Air enters the engine through the air cleaner and proceeds to the throttle plate. You control the amount of air that passes through the throttle plate and into the engine with the gas pedal.  It is then distributed through a series of passages called the intake manifold, to each cylinder
 At some point after the air cleaner, depending on the engine, fuel is added to the air-stream by either a fuel injection system or, in older vehicles, by the carburetor.

You have just read in detail about The Internal Combustion Engine
 which is found underneath the hood of your vehicle.

Below is a QUICK REVIEW of what you just learned.

SKIP The Review


Spark (match)
Compression (compacting)

1. Air and fuel enter the cylinder through the intake port opened by the intake valve.

The piston at this point is moving down the cylinder, thus creating a vacuum that helps draw in these two ingredients.

2. The piston then moves up the cylinder, compacting these ingredients tightly together. This insures a nice igniting of the materials for optimum explosive pressure afterwards.

3. The spark plug lights the air and fuel mixture.

This "igniting" makes the spark plug part of the ignition system

The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.

4. A controlled burning takes place in the cylinder just above the piston.

5. The exhaust, the garbage, leaves through the exhaust port and travels down the exhaust pipes.


Pressure from the newly created gases rapidly expanding push down on the piston, creating downward motion. Because the pistons are each connected to the crankshaft at different points, these downward movements turn this crankshaft.

The pistons push the crankshaft, and downward movement becomes circular movement.

Note that downward power has been changed to rotating power-a key technological advance paralleling the invention of the light bulb! The number of times the crankshaft revolves in a minute from this pushing is recorded by your dashboard's tachometer in revolutions per minute (rpm)
(see below).
This "tach" needle will hover around 800 when the engine is at idle, 2,000 when coasting, 2,500+ for accelerating or driving uphill.

This rotating crankshaft rotates the flywheel. The now rotating flywheel has lots of surface area from which the transmission can physically pick up and transmit this rotating power to the wheels.
The end result is that everything, including the wheels, rotates. And wheel rotation moves the car. It is sort of like a domino reaction, where one moving domino causes the next one to move. Here, the power from the piston causes the crankshaft to move, which causes the flywheel to move, then the transmission, then the drive axles, then the wheels.

Interestingly, by attaching a belt (NOT the timing Belt mentioned earlier) to the end of this revolving crankshaft, this rotating movement is utilized by other parts of the car.
For example, the now rotating belt moves the water pump, whose job it is to circulate the coolant through the engine. The belt also turns the alternator, which generates electricity for the battery and spark plugs.

Rotary engines work in a different way. 

The rotary, or Wankel, engine has no piston, it uses rotors instead (usually two). This engine is small, compact and has a curved, oblong inner shape (known as an "epitrochoid" curve). Its central rotor turns in one direction only, but it produces all four strokes (intake, compression, power and exhaust) effectively.

Explore The Rotary Engine



Types of Engines

There are two main kinds of automobile engines,
 the piston engine (which was discussed above)
and the rotary engine.
Both are internal-combustion engines, which means that fuel is burned inside the engine.

There are several piston engine types which are identified by the number of cylinders and the way the cylinders are laid out. Motor vehicles will have from 3 to 12 cylinders which are arranged in the engine block in several configurations.

The core of the engine is the cylinder, with the piston moving up and down inside the cylinder.  A car has more than one cylinder (four, six and eight cylinders are common).
In a multi-cylinder engine, the cylinders usually are arranged in one of three ways:

(also known as horizontally opposed or boxer)

The most popular of them are shown on the left.

An inline 4 cylinder engine

A V-6 cylinder engine



A flat 4 cylinder engine


In-line engines

In-line engines have the cylinders arranged, one after the other, in a straight line. In a vertical position, the number of cylinders used is usually either four or six, but three cylinder cars are becoming more common.


V-Type Engines

The V-type of engine has two rows of cylinders at (usually) a ninety degree angle to each other and is commonly used in V-6, V-8, V-10 and V-12 configurations.
Its advantages are its short length, the great rigidity of the block, its heavy crankshaft, and attractive low profile (for a car with a low hood). This type of engine lends itself to very high compression ratios without block distortion under load, resistance to tensional vibration, and a shorter car length without losing passenger room.

In 1914, Cadillac was the first company in the United States to use a V-8 engine in its cars.

Flat (Horizontal-Opposed) Engines

A horizontal-opposed engine is like a V-type engine that has been flattened until both banks lie in a horizontal plane. It is ideal for installations where vertical space is limited, because it has a very low height.

Flat engines are less common than the other two designs.  They are used in Subaru's and Porsches in 4 and 6 cylinder arrangements as well as in the old VW beetles with 4 cylinders.  Flat engines are also used in some Ferrari's with 12 cylinders.

Engine Components

Engine Block 

The purpose of the engine block is to support the components of the engine. Additionally, the engine block transfers heat from friction to the atmosphere and engine coolant.







What is the difference between a small block and a big block?
How about a short block and a long block?

Short Block: An engine WITHOUT the head(s). Usually includes the crankshaft, camshaft, and pistons.

Long Block: An engine WITH the head(s). Usually does not include the oil pan, valve covers, and manifolds.

Small Block: The smaller of a manufacturers two series of engines. In the case of Chevy, the small block includes the 262, 265, 267, 283, 302, 305, 307, 327, 350, and 400.

Big Block: The larger of a manufacturers two series of engines. In the case of Chevy, the 366, 396, 402, 427, and 454.

Notice the overlap of small and big block displacements. Note also that a small block can be a long block.
The terms define different characteristics of the engine.


A cylinder is a round hole through the engine block, bored to receive a piston (See Above Image). All automobile engines, whether water-cooled or air-cooled, four cycle or two cycle, have more than one cylinder. These multiple cylinders are arranged in-line, opposed, or in a V.
Engines for other purposes, such as aviation, are arranged in other assorted forms.

The diameter of the cylinder is called the "bore" while its height is called its "stroke." The "displacement" of an engine is actually a reflection of the total amount of volume of the engine's cylinders, and nothing to do with the actual size of the engine itself (although the two are highly correlated). The displacement is simply the bore multiplied by the stroke of a single cylinder, multiplied by the total number of cylinders in the engine. Muscle car engine displacements were usually measured in cubic inches, while modern vehicle's are expressed in terms of liters. Roughly 61 cubic inches equals a liter of displacement. Therefore, an engine with 350 cubic inches of displacement would be the equivalent of 5.7 liters.

The Cylinder Head

The Cylinder Head is the top cap for the engine block.
 The cylinder head is the metal part of the engine that encloses and covers the cylinders.

 Bolted on to the top of the block, the cylinder head contains combustion chambers, water jackets
 and valves (in overhead-valve engines).
The head gasket seals the passages within the head-block connection, and seals the cylinders as well.

Henry Ford sold his first production car, a 2-cylinder Model A, on July 23, 1903. 

The cylinder head contains at least one intake valve and one exhaust valve for each cylinder. This allows the air-fuel mixture to enter the cylinder and the burned exhaust gas to exit the cylinder.  Most engines have two valves per cylinder, one intake valve and one exhaust valve.

Some newer engines are using multiple intake and exhaust valves per cylinder for increased engine power and efficiency.
 These engines are sometimes named for the number of valves that they have such as "24 Valve V6" which indicates a V-6 engine with four valves per cylinder.  Modern engine designs can use anywhere from 2 to 5 valves per cylinder.

Camshaft and Lobes

The valves are opened and closed by means of a camshaft. A camshaft is a rotating shaft that has individual lobes for each valve. The lobe is a "bump" on one side of the shaft that pushes against a valve lifter moving it up and down.

See where they are found within The Engine

When the lobe pushes against the lifter, the lifter in turn pushes the valve open.  When the lobe rotates away from the lifter, the valve is closed by a spring that is attached to the valve.   A very common configuration is to have one camshaft located in the engine block with the lifters connecting to the valves through a series of linkages.  The camshaft must be synchronized with the crankshaft so that it makes one revolution for every two revolutions of the crankshaft. 
In most engines, this is done by a "Timing Chain" (similar to a bicycle chain) that connects the camshaft with the crankshaft. Newer engines have the camshaft located in the cylinder head  directly over the valves.  This design is more efficient but it is more costly to manufacture and requires multiple camshafts on Flat and V-type engines.  It also requires much longer timing chains or timing belts which are prone to wear.
 Some engines have two camshafts on each head, one for the intake valves and one for the exhaust valves.  These engines are called Double Overhead Camshaft (D.O.H.C.) Engines while the other type is called Single Overhead Camshaft (S.O.H.C.) Engines.  Engines with the camshaft in the block are called Overhead Valve (O.H.V) Engines.


Your head gasket is the gasket that separates the head of your engine from the block.
It also separates the coolant channels from the oil channels.

The small holes that you see around the piston holes are oil and coolant channels that allow the engine coolant to flow around the pistons for better cooling of the engine.

When the factories bolt the engine's head and block together, a small piece of rubbery material. the gasket is placed in between for a tightly sealed fit. Gaskets insure a firm seal. Occasionally, gaskets deteriorate to the point where they leak, particularly on very old cars and highly stressed racing cars. Perhaps you have heard someone say that their engine "blew a gasket" or has a "blown head gasket."

Gaskets and seals are needed in your engine to make the machined joints snug, and to prevent fluids and gasses (oil, gasoline, coolant, fuel vapor, exhaust, etc.) from leaking.

The cylinder head has to keep the water in the cooling system at the same time as it contains the combustion pressure. Gaskets made of steel, copper and asbestos are used between the cylinder head and engine block. Because the engine expands and contracts with heating and cooling, it is easy for joints to leak, so the gaskets have to be soft and "springy" enough to adapt to expansion and contraction.
They also have to make up for any irregularities in the connecting parts.

Overhead Camshaft (OHC)

Some engines have the camshaft mounted above, or over, the cylinder head instead of inside the block (OHC "overhead camshaft" engines). This arrangement has the advantage of eliminating the added weight of the rocker arms and push rods; this weight can sometimes make the valves "float" when you are moving at high speeds. The rocker arm setup is operated by the camshaft lobe rubbing directly on the rocker. Stem to rocker clearance is maintained with a hydraulic valve lash adjuster for "zero" clearance.

The overhead camshaft is also something that we think of as a relatively new development, but it's not. In 1898 the Wilkinson Motor Car Company introduced the same feature on a car.

Double Overhead Camshaft(DOHC)

The double overhead cam shaft (DOHC) is the same as the overhead camshaft, except that there are two camshafts instead of one.

Overhead Valve (OHV)

In an overhead valve (OHV) engine, the valves are mounted in the cylinder head, above the combustion chamber. Usually this type of engine has the camshaft mounted in the cylinder block, and the valves are opened and closed by push rods.

Multivalve Engines 

All engines have more than one valve; "multivalve" refers to the fact that this type of engine has more than one exhaust or intake valve per cylinder.

Intake Port

The passage in the cylinder head which connects the intake manifold to the intake valve through which the fuel-air mixture proceeds on its way to the cylinders.

Intake Valve

The poppet valve that opens to permit the fuel mixture into the cylinder.
Some engines have more than one intake valve to each cylinder

Poppet Valve

The valve used to open and close the valve port entrances to the engine cylinders.

The Valve Train

The valvetrain's only job is to let air and fuel in and out of the engine at the proper time. The timing is controlled by the camshaft which is synchronized to the crankshaft by a chain or belt.

Most cars built before the 1990s need to have their "timing"- the rhythm of the cams and crankshafts-adjusted once in a while.
On some cars you need only a timing light (less than $50) and a screwdriver.
Newer cars are computer-controlled and need no adjustments

The valve train is a precisely-timed mechanism made up of valves, rocker arms, pushrods, lifters, and the camshaft.

The function of the valvetrain is to allow fuel and air into the engine at the appropriate time. The camshaft controls the timing but this is synchronized to the crankshaft by the timing belt which is often referred to as the fan belt.

Engines are constantly being redesigned so that they are lighter and have relatively flat torque curves. Engine management systems improve engine economy and responses. Engines have been made quieter by introducing a torque roll axis mounting system which reduces engine vibrations.

Read More on 
The Valve System

Connecting Rod 


Connecting rods connect the piston to the crankshaft.
The upper end has a hole in it for the piston wrist pin and the lower end (big end) attaches to the crankshaft.

Connecting rods are usually made of alloy steel, although some are made of aluminum.

Connecting Rod Bearings

Connecting rod bearings are inserts that fit into the  connecting rod's lower end and ride on the journals of the crankshaft.


The crankshaft converts the up and down (reciprocating) motion of the pistons into a turning (rotary) motion.
It provides the turning motion for the wheels.
As the pistons move up and down, they turn the crankshaft just like your legs pump up and down to turn the crank that is connected to the pedals of a bicycle.

The crankshaft is usually either alloy steel or cast iron.
 The crankshaft is connected to the pistons by the connecting-rods. 

Some parts of the shaft do not move up and down; they rotate in the stationary main bearings. These parts are known as journals. There are usually three journals in a four cylinder engine.

The speed at which the crankshaft spins is measured in revolutions per minute (RPMs). Most drivers run their engines at three to five thousand RPMs. When the driver puts their foot on the accelerator, it lets more gasoline and air into the engine. Since most cars have computerized fuel delivery systems, instead of carburetors, the amount of air let in and fuel released is carefully calculated.        

The crankshaft is located below the cylinders on an in-line engine
at the base of the V on a V-type engine
between the cylinder banks on a flat engine.


The flywheel is a fairly large wheel (a heavy disc) that is attached to the rear of the crankshaft. It provides the momentum to keep the crankshaft turning without the application of power. It does this by storing some of the energy generated during the power stroke. Then it uses some of this energy to drive the crankshaft,  connecting rods and pistons during the three idle strokes of the 4-stroke cycle. This makes for a smooth engine speed. The flywheel forms one surface of the clutch and is the base for the ring gear.


Main Bearings

The crankshaft is held in place by a series of main bearings. The largest number of main bearings a crankshaft can have is one more than the number of cylinders, but it can have one less bearing than the number of cylinders.

Not only do the bearings support the crankshaft, but one bearing must control the forward-backward movement of the crankshaft. This bearing rubs against a ground surface of the main journal, and is called the "thrust bearing."


The combustion chamber is the area where compression and combustion take place. As the piston moves up and down, you can see that the size of the combustion chamber changes. It has some maximum volume as well as a minimum volume.
The difference between the maximum and minimum is called the displacement and is measured in liters or CCs (Cubic Centimeters, where 1,000 cubic centimeters equals a liter).

Here are some examples: 

A chainsaw might have a 40 cc engine. 

A motorcycle might have a 500 cc or a 750 cc engine. 

A sports car might have a 5.0 liter (5,000 cc) engine.

Most normal car engines fall somewhere between 
1.5 liter (1,500 cc) and 4.0 liters (4,000 cc)

If you have a 4-cylinder engine and each cylinder displaces half a liter, then the entire engine is a "2.0 liter engine." If each cylinder displaces half a liter and there are six cylinders arranged in a V configuration, you have a "3.0 liter V-6."

Generally, the displacement tells you something about how much power an engine can produce. A cylinder that displaces half a liter can hold twice as much fuel/air mixture as a cylinder that displaces a quarter of a liter, and therefore you would expect about twice as much power from the larger cylinder (if everything else is equal).
So a 2.0 liter engine is roughly half as powerful as a 4.0 liter engine. 

You can get more displacement in an engine either by increasing the number of cylinders or by making the combustion chambers of all the cylinders bigger (or both).

Combustion Chamber 

As the name suggests, this is the area where the compressed air/fuel mixture is ignited and burned. 

 The location of the combustion chamber is the area between the top of the piston at what is known as TDC (top dead center) and the cylinder head. TDC is the piston's position when it has reached the top of the cylinder, and the center line of the  connecting rod is parallel to the cylinder walls.

The two most commonly used types of combustion chamber are the hemispherical and the wedge shape combustion chambers.

The hemispherical type is so named because it resembles a hemisphere. It is compact and allows high compression with a minimum of detonation. The valves are placed on two planes, enabling the use of larger valves. This improves "breathing" in the combustion chamber. This type of chamber loses a little less heat than other types. Because the hemispherical combustion chamber is so efficient, it is often used, even though it costs more to produce.

The wedge type combustion chamber resembles a wedge in shape. It is part of the cylinder head. It is also very efficient, and more easily and cheaply produced than the hemispherical type.


Horsepower is a unit of power for measuring the rate at which a device can perform mechanical work. Its abbreviation is hp or bhp (for brake horse power). One horsepower was defined as the amount of power needed to lift 33,000 pounds one foot in one minute.

Piston rings

Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:

They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.

They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.

Most cars that "burn oil" and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly.

Wrist Pin 

The wrist pin connects the piston to the  connecting rod.
The connecting rod comes up through the bottom of the piston. The wrist pin is inserted into a hole (about half way up) that goes through the side of the piston, where it is attached to the connecting rod.


Timing refers to the delivery of the ignition spark, or the opening and closing of the engine valves, depending on the piston's position, for the power stroke. The timing chain is driven by a sprocket on the crankshaft and also drives the camshaft sprocket.


Timing Chain/belt

The automobile engine uses a metal timing chain, or a flexible toothed timing belt to rotate the camshaft. The timing chain/belt is driven by the crankshaft. The timing chain, or timing belt is used to "time" the opening and closing of the valves. The camshaft rotates once for every two rotations of the crankshaft.

Push Rods

Push Rods attach the valve lifter to the rocker arm. Through their centers, oil is pumped to lubricate the valves and rocker arms.

Serpentine Belts

A recent development is the serpentine belt, so named because they wind around all of the pulleys driven by the crankshaft pulley.
This design saves space, but if it breaks, everything it drives comes to a stop.

Harmonic Balancer
(Vibration Damper)

The harmonic balancer, or vibration damper, is a device connected to the crankshaft to lessen the torsional vibration. When the cylinders fire, power gets transmitted through the crankshaft. The front of the crankshaft takes the brunt of this power, so it often moves before the rear of the crankshaft. This causes a twisting motion. Then, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Although this unwinding process is quite small, it causes "torsional vibration." To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft that's causing all the trouble. The balancer is made of two pieces connected by rubber plugs, spring loaded friction discs, or both.

When the power from the cylinder hits the front of the crankshaft, it tries to twist the heavy part of the damper, but ends up twisting the rubber or discs connecting the two parts of the damper. The front of the crank can't speed up as much with the damper attached; the force is used to twist the rubber and speed up the damper wheel.
This keeps the crankshaft operation calm.

Engine Balance

Flywheel  A 4 cylinder engine produces a power stroke every half crankshaft revolution, an 8 cylinder, every quarter revolution.  This means that a V8 will be smoother running than a 4.  To keep the combustion pulses from generating a vibration,  a flywheel is attached to the back of the crankshaft.  The flywheel is a disk that is about 12 to 15 inches in diameter. On a standard transmission car, the flywheel is a heavy iron disk that doubles as part of the clutch system. On automatic equipped vehicles, the flywheel is a stamped steel plate that mounts the heavy torque converter.
The flywheel uses inertia to smooth out the normal engine pulses.

Balance Shaft  Some engines have an inherent rocking motion that produces an annoying vibration while running.  To combat this, engineers employ one or more balance shafts. A balance shaft is a heavy shaft that runs through the engine parallel to the crankshaft. This shaft has large weights that, while spinning, offset the rocking motion of the engine by creating an opposite rocking motion of their own.


Heat is the unwanted byproduct. Engineers design a car to diffuse the heat quickly and efficiently before it damages or melts the engine. Coolant (also known as antifreeze), stored in the radiator, flows through passages in the engine around the cylinders where it absorbs heat from the combustion mixture. Coolant is part water, and part pure coolant (ethylene glycol), a chemical makeup allowing optimum heat absorption. The coolant carries this heat through hoses to the radiator where flowing air removes the heat, restoring the coolant to its original temperature, and leaving it ready to absorb more heat. This continuous closed cycle of heat transportation prevents the engine from melting together or seizing up due to the extremely high temperatures produced from combustion (1,000 degrees F+). The water pump, running from the belt system, helps circulate this coolant.
When you need heat in the passenger area, you are asking that some of this same heat be diverted to your space.
(By the way, coolant retains its "antifreeze" name because it also prevents this water mixture from freezing up into an ice cube in the winter time.)

Oil, stored in the oil pan below the engine, flows through its own passages in the engine's block absorbing and transferring heat. More importantly, oil prevents heat buildup by reducing friction. If you rub your hands together, note how quickly they generate heat and become warm. Friction produces heat. If you were to cover your hands in vegetable oil first, the result of rubbing would be little or no heat because direct contact between your hands is reduced.


Engines run on a vacuum system.

A vacuum exists in an area where the pressure is lower than the atmosphere outside of it. Reducing the pressure inside of something causes suction.
For example, when you drink soda through a straw, the atmospheric pressure in the air pushes down on your soda and pushes it up into your mouth.
The same principal applies to your engine. When the piston travels down in the cylinder it lowers the atmospheric pressure in the cylinder and forms a vacuum. This vacuum is used to draw in the air and fuel mixture for combustion. The vacuum created in your engine not only pulls the fuel into the combustion chamber, it also serves many other functions.

The running engine causes the carburetor and the intake manifold to produce "vacuum power," which is harnessed for the operation of several other devices.

Vacuum is used in the ignition-distributor vacuum-advance mechanism. At part throttle, the vacuum causes the spark to give thinner mixtures more time to burn.

The positive crankcase ventilating system (PCV) uses the vacuum to remove vapor and exhaust gases from the crankcase.

The vapor recovery system uses the vacuum to trap fuel from the carburetor float bowl and fuel tank in a canister. Starting the engine causes the vacuum port in the canister to pull fresh air into the canister to clean out the trapped fuel vapor.

Vacuum from the intake manifold creates the heated air system that helps to warm up your carburetor when it's cold.

The EGR valve (exhaust-gas recirculation system) works, because of vacuum, to reduce pollutants produced by the engine.

Many air conditioning systems use the vacuum from the intake manifold to open and close air-conditioner doors to produce the heated air and cooled air required inside your vehicle.

Intake manifold vacuum also is used for the braking effort in power brakes. When you push the brake pedal down, a valve lets the vacuum into one section of the power-brake unit. The atmospheric pressure moves a piston or diaphragm to provide the braking action.

Firing Order

Now each cylinder produces its own combustion recipe at its own separate time dictated by the firing order. For example, my 1984 Chevy Pick Up firing order is: 1-5-3-6-2-4.
This firing information can be found just inside the hood on one of those numerous stickers,
or in any manual specific to your vehicle.
This firing order means that cylinder one burns or fires its mixture first, then cylinder four, then cylinder two, then cylinder five, etc. until it goes back to cylinder one and repeats the whole process. Your car's computer makes sure that each cylinder has the necessary mixture at the right time.

Powertrain Control Module

The intake valves rely on "valve timing" to open their ports at the correct time for the air and fuel ingredients. Valve timing at this point is mechanically controlled by the camshaft. But the spark plug needs to know when to ignite the mixture, matching the valve openings, and so relies on the "ignition timing" set by the car's computer.

You may not be computer literate, but your car is. All cars nowadays have a computer tucked away under the dash or hood. Known as the powertrain control module (PCM), this computer insists on the most precise combustion mixture to insure the best gas mileage and reduce tailpipe pollutants. The computer has its eyes and ears around the car via its sensors which are strategically placed in order to capture certain data.
In this manner, the PCM controls the amount and timing of combustion ingredients, and therefore, the final results.

This PCM also provides important data to you via your dashboard gauges, needles, and lights.

There are many variations among dashboards-some use a light 
in place of a gauge and vice versa, 
or combine the two into one general purpose dash indicator.

 Check with your driver's manual for an accurate understanding of your specific gauges and lights.

The red "check engine" light flags an oil, coolant, or engine problem that needs immediate attention. Treat this light very seriously!
On some older cars, this light may identify an oil, coolant, or emissions problem.
 Newer cars use the separate, 

gold/orange "service engine" light for emissions-related problems. The golden/orange-colored "service engine" light may also illuminate if there is a computer problem. Either is hazardous both to your engine and your emissions system and will increase air pollution out the tailpipe. Again, this light requires prompt attention.

The oil gauge shown above reveals oil pressure. Some gauges show oil level instead, some show an oil can

 so check your driver's manual for variations. 
Your car may not have either one, relying entirely on the red engine light for oil problems.

The battery gauge above indicates the battery charge, which should hover between 12.6 and 14.5 volts. Anything over 14.5 volts is too much for your car's computer.

The temperature gauge registers your engine's temperature.

The rpm needle (tachometer) measures the revolutions of your crankshaft.

If your car is equipped with an antilock brakes system (ABS),

then the ABS light may come on initially as the computer checks the system.
It should then go out.

The same goes for the airbag light, again, 
if your car is equipped with one or more airbags.


Pistons form a combustion seal and transmit forces from combustion to the  connecting rods. The piston is a partly hollow, cylindrical shaped piece of metal that fits relatively tightly inside a cylinder

Most common engines have 4, 6, or 8 pistons which move up and down in the cylinders.
On the upper side of the piston is what is called the combustion chamber where the fuel and air mix before ignited.  On the other side is the crankcase which is full of oil.  Pistons have rings which serve to keep the oil out of the combustion chamber and the fuel and air out of the oil.

All the pistons in the engine are connected through individual connecting rods to a common crankshaft.

See where the piston is located in The Engine
Click Here


An engine has a number of systems that help it do its job of converting fuel into motion. Most of these subsystems can be implemented using different technologies, and better technologies can improve the performance of the engine. Here's a look at the different subsystems used in modern engines:

Ignition System

The ignition system produces a high-voltage electrical charge and transmits it to the spark plugs via ignition wires.

The charge first flows to a distributor, which you can easily find under the hood of most cars. The distributor has one wire going in the center and four, six, or eight wires
 (depending on the number of cylinders)
coming out of it. 

These ignition wires send the charge to each spark plug. The engine is timed so that only one cylinder receives a spark from the distributor at a time. This approach provides maximum smoothness.

Click here to explore The Ignition System

Cooling System

Internal combustion engines must maintain a stable operating temperature, not too hot and not too cold.  With the massive amounts of heat that is generated from the combustion process, if the engine did not have a method for cooling itself, it would quickly self-destruct.  Major engine parts can warp causing oil and water leaks and the oil will boil and become useless.

The cooling system in most cars consists of the radiator and water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off.

In a few cars, as well as most bikes, the engine is air-cooled instead. You can tell an air-cooled engine by the fins adorning the outside of each cylinder to help dissipate the heat. Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance.

Click here to explore The Cooling System

Air Intake System

Most cars are normally aspirated, which means that air flows through an air filter and directly into the cylinders.

High-performance engines are either turbo charged or super charged, which means that air coming into the engine is first pressurized (so that more air / fuel mixture can be squeezed into each cylinder) to increase performance. The amount of pressurization is called boost.

A turbo charger uses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. A super charger is attached directly to the engine to spin the compressor.


Click here to explore the Air Filter System

  Starting System

The starting system consists of an electric starter motor and a starter solenoid. When you turn the ignition key, the starter motor spins the engine a few revolutions so that the combustion process can start.

It takes a powerful motor to spin a cold engine. The starter motor must overcome: 

All of the internal friction caused by the piston rings.

The compression pressure of any cylinder(s) that happens to be in the compression stroke.

The energy needed to open and close valves with the cam shaft.

All of the "other" things directly attached to the engine, like the water pump, oil pump, alternator, etc.

Because so much energy is needed and because a car uses a 12-volt electrical system, hundreds of amps of electricity must flow into the starter motor. The start solenoid is essentially a large electronic switch that can handle that much current.
When you turn the ignition key, it activates the solenoid to power the motor. 

The Engine's Lubrication System

Oil is the life-blood of the engine.
 An engine running without oil will last about as long as a human without blood. 
Oil is pumped under pressure to all the moving parts of the engine by an oil pump. 

The lubrication system makes sure that every moving part in the engine gets oil so that it can move easily. The two main parts needing oil are the pistons (so they can slide easily in their cylinders) and any bearings that allow things like the crankshaft and cam shafts to rotate freely.

In most cars oil is sucked out of the oil pan by the oil pump, run through the oil filter to remove any grit, and then squirted under high pressure onto bearings and the cylinder walls. The oil then trickles down into the sump, where it is collected again and the cycle repeats.

Click Here to explore The Lubrication System
Facts About Motor Oil 

Fuel System

The fuel system pumps fuel from the fuel tank and mixes it with air
 so that the proper air/fuel mixture can flow into the cylinders.
 Fuel is delivered in three common ways: 
port fuel injection
direct fuel injection.

In carburetion a device called a carburetor mixes fuel into air as the air flows into the engine. 

In a fuel injected engine the right amount of fuel is injected individually into each cylinder either right above the intake valve (port fuel injection) or directly into the cylinder (direct fuel injection).

Exhaust System

Exhaust, the garbage of the whole piston process, is vented out through the exhaust ports to the exhaust pipes, muffler, and tailpipe.

The exhaust system includes the exhaust pipe and the muffler. Without a muffler what you would hear is the sound of thousands of small explosions coming out your tailpipe. A muffler dampens the sound. The exhaust system also includes a catalytic converter.

Explore on The Webpage covering exhaust

  Emission Control System

The emission control system in modern cars consists of a catalytic converter, a collection of sensors and actuators, and a computer to monitor and adjust everything.

For example, the catalytic converter uses a catalyst and oxygen to burn off any unused fuel and certain other chemicals in the exhaust. An oxygen sensor in the exhaust stream makes sure there is enough oxygen available for the catalyst to work and adjusts things if necessary.

  Electrical System

The electrical system consists of a battery and an alternator.
The alternator is connected to the engine by a belt and generates electricity to recharge the battery. 

The battery makes 12-volt power available to everything in the car needing electricity
 (the ignition system, radio, headlights, windshield wipers, power windows and seats, computers, etc.) through the vehicle's wiring.


So you go out one morning and your engine will turn over but it won't start . . .

What could be wrong?


Should your mechanic ever say,
"You've got a worn piston," or "Your block is cracked,"
now you'll know what they mean.

 A worn piston means the "lid" that converts the explosion into usable energy is allowing some of the energy to slip by.
A cracked block means the "can" is no longer containing the energy.

 Now that you know how an engine works, you can understand the basic things that can keep an engine from running.
Three fundamental things can happen: a bad fuel mix, lack of compression or lack of spark. Beyond that, thousands of minor things can create problems, but these are the "big three."
Based on the simple engine we have been discussing,
 here is a quick run-down on how these problems affect your engine: 

1. Bad fuel mix - A bad fuel mix can occur in several ways:

  • You are out of gas, so the engine is getting air but no fuel. 

  • The air intake might be clogged, so there is fuel but not enough air. 

  • The fuel system might be supplying too much or too little fuel to the mix, meaning that combustion does not occur properly.

  • There might be an impurity in the fuel (like water in your gas tank) that makes the fuel not burn.

  2. Lack of compression - If the charge of air and fuel cannot be compressed properly, the combustion process will not work like it should. Lack of compression might occur for these reasons:

  • Your piston rings are worn (allowing air/fuel to leak past the piston during compression).

  • The intake or exhaust valves are not sealing properly, again allowing a leak during compression.

  • There is a hole in the cylinder.

The most common "hole" in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks.

3. Lack of spark - The spark might be nonexistent or weak for a number of reasons:

  • If your spark plug or the wire leading to it is worn out, the spark will be weak. 

  • If the wire is cut or missing, or if the system that sends a spark down the wire is not working properly, there will be no spark.

  • If the spark occurs either too early or too late in the cycle (i.e. if the ignition timing is off), the fuel will not ignite at the right time, and this can cause all sorts of problems.

Other Problems

Many other things can go wrong. For example: 

  • If the battery is dead, you cannot turn over the engine to start it. 

  • If the bearings that allow the crankshaft to turn freely are worn out, the crankshaft cannot turn so the engine cannot run.

  • If the valves do not open and close at the right time or at all, air cannot get in and exhaust cannot get out, so the engine cannot run.

  • If someone sticks a potato up your tailpipe, exhaust cannot exit the cylinder so the engine will not run.

  • If you run out of oil, the piston cannot move up and down freely in the cylinder, and the engine will seize.

In a properly running engine, all of these factors are within tolerance. 

As you can see, an engine has a number of systems that help it do its job of converting fuel into motion. Most of these subsystems can be implemented using different technologies, and better technologies can improve the performance of the engine.


Try and detect the problem - is the car not starting, running roughly, conking out, or using too much petrol?

After you have detected it, isolate the system most likely to be its cause. If it is conking out, the fuel system may be at fault. If it is not starting, the electrical system may be worth looking at first. If the car is overheating, check the cooling system.

After you have isolated the most likely system, locate the weakest link in that system. The fuel pump, for example, is often the most vulnerable part of the fuel system.

Check each successive part in the system until the problem is solved. 

Get the broken part replaced or repaired. Consult your car's manual for other specific problems you might be facing.
 This will help to speed up diagnosis

Other Problems you might encounter with the mentioned parts

Pistons: The rings over time tend to wear out.  When they wear they allow the fuel and air to enter into the oil and dilute it.  This dilution reduces the oils ability to lubricate your engine and can cause premature wear.  Also if the rings wear down they can allow oil from the crankcase to enter the combustion chambers.  This will result in oil being burned and exiting your tailpipe as grayish/white smoke.  If your car spews grayish white smoke and it does not go stop in the first few minutes after start-up you might have worn rings.  If the smoke goes away after start-up look to the valvetrain section.

Crankshaft The crankshaft rides on bearings which can wear down over time.  The bearings support the crankshaft and also the rods which connect the pistons to the crankshaft.  A loud medium pitched knocking noise in the engine points to warn bearings most of the time.  This is usually a costly repair and involves removing the crankshaft and either machining the surface where the bearings ride, or replacing the entire crankshaft.  To prevent this type of problem, use a high quality oil, change your oil at suggested intervals (3 months or 3000 miles is a safe number) and always maintain your oil level between oil changes.

Valvetrain:  Remember the oil smoke problem mentioned above in the piston sections.  If your car only smokes grayish/white smoke at start-up you may have leaking valve seals.  Valve seals keep oil from above the valve from leaking into the combustion chamber.  When they wear, they can allow oil to seep into the combustion chamber and collect there until your start the engine again.  You generally do not get oil leaking past the valve seals while the engine is running since the seals expand with the heat of the engine and plug the leak. 

      Another common problem is the timing chain or belt will slip or even break causing the cam shaft to stop rotating.  Remember the camshaft tells the valves when to open and if it stops spinning then the valves stop opening and closing.  No valve moving, no engine running :-)   

     A term you will here when talking about timing chains and belts is "interference engine".  When an engine is an "interference engine" the pistons and valves are so close together that if the valves were to stop moving (broken belt or chain) and the crankshaft kept spinning they would crash into the piston. (that's the interference)  This crash tends to do bad things to an engine, breaking valve, bending pushrods, and even cracking pistons.  This is why most manufacturers recommend changing the timing chain or belt every 60,000 miles.  timing belts dry out, stretch and deteriorate over time so even if you do not have 60,000 miles on the car think about changing the belt after it's 6 years old.  

Check your Engine Condition on a Regular Basis

Generally, most of engine breakages happen as the result of the owner's mistakes. If your car has run well for many years, you might find yourself skipping a fluid check or putting longer periods of time between the engine servicing's. Today, with self-service gas stations everywhere, often the only way you will insure your car's fluids are at proper levels is to do it yourself. If you don't, you may miss a minor defect, for example, a coolant leakage. A few weeks later, lack of the coolant causes your engine to overheat and eventually you are faced with engine damage. And then even after that repair, other small problems surface and you find that your car breaks down more often.
It's important for you to safeguard your vehicle investment by checking your engine condition on a regular basis.

What's Needed to Keep the Engine in Good Condition?

Actually, only few basic conditions are needed for long engine life:

 Good engine lubrication

         - Perform timely oil Changes and oil filter changes and use only high quality oil and oil filters

          - Check your garage floor or parking space for visible signs of fluid leakage

 Prevent the engine from overheating

          - Periodically check the cooling system, the coolant level, and radiator

 Perform engine maintenance and tune up according to the owners' manual schedule

          - Provide necessary cleanings and adjustments (drive belt tension, valve cleaning, etc)

          - Provide necessary replacements (timing belts, air filters, spark plugs, etc)

 Immediately eliminate any minor engine defects

Start by Checking the Engine Condition

Routinely listen for noises when your engine is running. The engine should run evenly and you should not hear any strong noises, knocking, pinging, or whistling while the engine is idling or during acceleration.   After it's warmed up, try to press accelerator harshly for a second. The engine should accelerate quickly, without delays or hesitation. There should be no loud noises while accelerating. The idle should be stable during a stop. There should be no smoke coming out from the tail pipe (only steam during warming up or in cold weather is permissible).

Look at the instrument panel. All the warning lights on the instrument panel for low oil pressure, check engine, overheating, etc should go off after the engine is started and should not come on while the engine is running.

Open the hood and look at the engine. A good engine should be dry. It may be dusty, but it should not be oily, and it should not have any leaks. Check the engine thoroughly for oil leaks. The more leaks, the more damage your engine may have.

When performing routine engine maintenance and tune ups, cleanings, adjustments, and necessary replacements, check for the following:

 Fuel Filter: A dirty fuel filter may cause unexpected engine stalling and loss of engine power.

 Air Filter: A dirty air filter dirty air filter causes loss of engine power, increased fuel consumption, etc

 Spark Plugs: replacement can give significant enhancement of engine performance.

 Timing Belt: Timing Belt damage can cause serious engine damage, especially if it's a diesel engine.

 Engine Coolant: Old coolant loses its anticorrosive and other characteristics.


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The objective of this Web Page is to familiarize you with basic auto maintenance
-  in some common emergencies -
not to make you an expert in auto mechanics

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 I am in no way, shape, or form telling you to do this yourself. Your results may vary. If something goes wrong, it is not my fault!
These are just guidelines.