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Air Cleaner & Filter

Changing your car's filters on a regular basis can have a significant impact on engine life and performance

What Does The Air Cleaner Do?   Air Cleaner Components    Inspect The Air Filter      How often should I replace my air filter?
 Change The Air Filter Element:

Preventative Maintenance Check List
Keep a Maintenance Record




What Does The Air Cleaner Do?

The purpose of the engine air filter is to clean the enormous amount of air used by the engine. It must filter out airborne dust and dirt that would otherwise enter the engine and cause premature wear.

Even during low speed operation, the engine pulls in a tremendous volume of air. This air has a great deal of abrasive particles, which must be prevented from entering the engine.
 The air cleaner traps the abrasive particles before they can enter the engine. In so doing, however, it clogs itself.

The air filter and positive crankcase ventilation (PCV) valve are important parts of your vehicle's fuel system. The air filter provides clean air to a vehicle's carburetion system, and if it becomes clogged or dirty, it can cause your car to idle or run roughly and reduce gas mileage.

The PCV valve helps prevent the release of gas fumes from the engine. If it becomes blocked or clogged, it can cause oil leaks and promote the formation of sludge in the engine

 The air filter should be checked every other month.
If the air filter is not changed regularly, it can become so clogged that it limits air flow into the engine.


Why Change My Air Filter?

Your air filter performs two of the toughest jobs for your car: protecting the engine from contaminants and providing clean air for the engine.

Contaminants in the air can cause serious damage to engine parts. Your air filter traps dirt, dust, sand and microscopic exhaust particles and protects them from entering your engine.

For every gallon of gasoline it burns, your engine consumes 12,000 gallons of outside air. Your air filter must clean all of it. Its job is to allow a sufficient flow of air to keep combustion working at peak levels to ensure the best performance of your engine.

What does a clean air filter do for your car? 

Extends the life of your engine

Increases gas mileage

Increases horsepower

Allows easier engine starts


do I change the darn thang?



Air Cleaner Components

The air cleaner has two main components

The parts of a typical air cleaner.


A housing provides a container for the filter element. The housing is a metal container that is typically mounted on top of the engine. Air is routed into the housing through an intake tube assembly. The intake tube assembly on the air cleaner housing shown above is a simple tube. On late-model cars, the intake tube assembly may be very complex and control the temperature of the incoming air for performance and emission control.

Intake tube and duct systems are complex on late-model cars

The filter is the part inside the housing that cleans the air. The two basic types of filters are the paper and oil-wetted polyurethane. Heavy duty filters sometimes combine both types of filter types.

Parts of a paper filter for an air cleaner.

The filter element is made from pleated paper. The pleats provide the maximum surface area for air to pass through. A fine mesh screen is used to support the paper element and protect against the fire hazards of an engine backfire. A top and bottom seal provides an airtight seal for the filter in the housing. Sealing is important because any air that does not go through the filter on the way into the engine could contain dirt.


Polyurethane is a flexible foam-type material. It can be used to filter air entering the engine. It is usually wetted with oil to improve its filtering ability. Filters used in very dirty conditions are often made of polyurethane and paper in combination. Incoming air is routed first through the polyurethane filter, then through the paper filter.

Replacement air filters are available for most vehicles. The filter has a part number printed on the filter box. Application charts are available in auto parts stores that show what number filter fits any particular car. Application charts are often printed on the filter box, too.

Inspect The Air Filter

Cars with fuel injection typically have an air filter element located in an air induction assembly like the one shown below

Typical air cleaner assembly on a fuel injection system

The filter element is located in a rectangular box called the air cleaner housing.
To find a rectangular air cleaner,
 follow the large air inlet hose away from your engine.

Find the air filter housing right near the beginning of the ductwork

 Look for the common black, semi-rectangular boxy container.
 Some Chryslers have a cylindrical shape; some Chevys compact a tissue sized box up against front wall behind one of the headlights. This type is on a track where you must slide the box up for filter.

Remove the filter lid, and lift out the filter.
Note the corrugated Paper usually  faces downward.

These are the three basic types of air filters; there are many slight variations

Remove the lid by either prying off clips or clamps with a flathead screwdriver; removing several large screws by hand or removing regular sized screws with either type of screwdriver.
Again, there are three basic types of lid holders with other slight variations out there.

Cars with carburetors or throttle body fuel injection often have a large round air cleaner assembly mounted on top of the carburetor.
The filter is located inside the air cleaner housing. 


How often should I replace my air filter? 


Air filters have always required periodic maintenance. An automotive engine runs much smoother when the air filter is clean. If the filter is wet, damaged, or dirty, it should be replaced with a new one designed specifically for your engine.

Running your car with a clogged filter could result in hard stalling, stalling and poor gas mileage. An air filter may become clogged or loaded with contaminate quicker, depending on the nature of the area where the vehicle is driven, such as dusty conditions.

A damaged filter can cause the engine to have excessive wear.


It's hard to give a specific time or mileage figure because the life of the filter depends on how much crud it ingests. A filter that lasts 20,000 or even 30,000 miles on a vehicle that's driven mostly on expressways may last only a month or two in a rural setting where the vehicle is driven frequently on gravel roads. Changing it annually or every 15,000 miles for preventative maintenance may be a good recommendation for the city driver, but not its country cousin.

Regardless of the mileage or time, a filter should be replaced before it reaches the point where it creates a significant restriction to airflow.
 But when exactly that point is reached is subject to opinion.

A slightly dirty filter actually cleans more efficiently than a brand new filter. That's because the debris trapped by the filter element helps screen out smaller particles that try to get through. But eventually every filter reaches the point where it causes enough of a pressure drop to restrict airflow. Fuel economy, performance and emissions begin to deteriorate and get progressively worse until the dirty filter is replaced.

When inspecting or changing the air filter element, first look up the procedure in the shop service manual. The manual will explain the specific procedure for removing and replacing the element.

To see whether your air filter needs to be replaced, just lift it out
(it isn't fastened down)

and hold it up to the sun or to a strong light.
 Can you see the light streaming through it?

If it's really caked with dirt, it obviously needs to be replaced. 

Trying to shake or blow the dirt out is a waste of time because too much of it will be embedded in the filter fibers.

Don't blow through the filter - you can foul it up that way



 It is better not to try to clean the paper air filter element; instead, replace it with a new one. Most paper elements are usually cleaned by tapping them on the ground to shake out the dirt or by blowing them with an air hose from the inside out. You can do more harm than good by attempting to clean the element this way, because once the filter is put back in place and the engine is started up, particles of dirt that were lodged in the element and consequently loosened by the tapping or air blowing are sucked into the engine. Abrasive grit can do lots of harm to an engine; in fact, abrasive wear is the most common cause of engine failure To help prevent it, DO NOT attempt to clean the air filter element. An air filter element is relatively inexpensive and is cheap insurance against the ravages of dirt and grit.

(This advice doesn't apply, of course, if you have an oil-bath or an oil-soaked air cleaner element.)

NOTE: Many filters that appear to be dirty are in fact still good and do not really need to be replaced. So it's up to you.
If you think it's dirty, replace it. 
If you don't think it's dirty enough to need replacing, then don't.

How to Change The Air Filter

Changing your car's filters on a regular basis can have a significant impact on engine life and performance
is one of the easiest things you can do!

 Pre 1990 Vehicle     1990 and Newer Vehicle

If you have an older car, the air filter is in a big round housing on top of the engine. These are very simple to change.

Simply unscrew the wing nut holding the cover down and lift it off. There may be three or four clips holding down the cover as well. Just unsnap the clips as well.

There you'll find the air filter inside.

Remove the top of the air cleaner by taking off a single wing nut as shown below

Typical air cleaner assembly on a carburetor system

   All you need do now is remove the old air filter and install the new one.
Make sure it is the right air filter for the car. If it is too big, the cover will not go back on and if it is too small, the cover will not seal to the top of the filter.

   Now, change the breather element.

In newer cars, the air filters are generally rectangular in shape and involve a little more work to get to. Look for a rectangular shaped housing under the hood. It will usually be located on one of the fender wells or over the radiator area. On most Chrysler 4 cylinder engines, it's located between the engine and the firewall. Cover attachments vary; on some there will be four or six screws around the outside edge.

There may be four clips or a combination of both. Use the appropriate tools to open the cover and remove the air filter. Be careful not to let any dirt or debris fall into the bottom of the housing. When you install the new air filter, reattach the air filter housing and be careful not to over tighten the holding screws.

Be patient, as this sometimes requires a bit of maneuvering and adjusting. The filter likes to pop out here and there.
With Chevy's,  getting the filter box onto the track takes more finagling. The less patient you are, the more it hassle and resist you!

   Air filters of this type do not have a breather filter since the PCV inlet is below the air filter. You should still check the PCV and be sure it's in good shape.

Note that a black and oily-wet air filter signifies a problem with your positive crankcase ventilation (PCV) valve.
Check and remedy the situation promptly before the oil contaminates your sensors.


A light coat of grease on the air cleaner gasket of an older car can improve the seal between the air cleaner housing and the air filter element.

A few older automobiles have permenant air filters and you will need to clean according to the instructions found in your owner's manual.

WARNING: The air filter gasket must fit correctly and seal properly. A leak at the gasket means that air will go directly into the engine around the gasket without going through the filter element. Abrasives can get into the engine and shorten engine life.

You should change your air filter once a year or every 20,000 miles, whichever comes first.
Unless yours gets very dirty before then.

Replace the crankcase breather filter at the same time if it's dirty.

Check the PCV valve and any related hoses whenever you check or replace the air filter.

It's also a good idea to check the fuel filter, spark plugs, points, condenser, cap, rotor and wires.

Changing Crankcase Breather Element

This filter is located in the air filter housing and can be checked at the same time as the air filter.
Most breather elements come in a plastic holder with a fitting that goes through the side of the air filter housing.

"Remove lid of air filter housing and remove air filter. Disconnect crankcase breather hose. Remove metal clip and save, unless it is supplied with the new element.

"Normal replacement is with air filter. If dirty on inspection, replace.

Install new breather element and secure with clip. Connect breather hose. Replace air filter and lid of filter housing, and tighten wing nut.


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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.

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