Haynes How-To: change an engine's air filter

Sections

• What is an engine’s air filter?
• Why does the engine air filter need changing?
• How often should the filter be changed?
• How do you replace an engine’s air filter?

What is an engine’s air filter?

An engine’s air filter is rather a person’s lungs. Without the filter, your car can’t run properly and may incur serious damage.

It should not be confused with the filter that is used within the heating and ventilation system. As the name suggests, it is designed to filter all the air that is taken into heart of the engine, before it is mixed with fuel and ignited or compressed to power you along the road.

A good air filter will prevent dust and debris from entering the heart of the engine while providing good airflow for the air intake system. They can be made from either paper, foam or oiled cotton.

Why does the engine air filter need changing?

If the air filter is not fitted, or incorrectly installed, it can let debris into the precious areas of the engine and could cause costly damage.

Equally, if the filter becomes dirty over time – can you remember when it was last replaced? – it can hamper the airflow into the engine, restricting performance.

It should be noted that certain air filter manufacturers, which use oiled cotton components, say their part can be washed, returning it to as good as new condition.

How often should the filter be changed?

Vehicles manufacturers provide maintenance schedules for every model of car. This can vary, so read the vehicle’s service book, which will itemise the jobs that need doing over time. Typically, the engine’s air filter would be replaced every year. However, some long-life service schedules may see that extended to once every 18 months.

How do you replace an engine’s air filter?

Tools you will need (click to view at Halfords.com)

• Screwdriver or socket set

Parts you will need (click to view at Halfords.com)

• Air filter

Caution: Never drive the vehicle with the air cleaner filter element removed. Excessive engine wear could result, and backfiring could cause a fire under the bonnet
Below is an example video but look for a full step-by-step guide for your specific car at Haynes OnDemand, here.

A quick guide to changing an engine air filter

1. Make sure the engine is cold and that you have the correct tools for the job.
2. The air filter element is located in the air filter housing in the engine compartment. The vehicle handbook will show its location
3. Check there is no debris in the housing that could fall into the filter compartment as you lift the housing away. If there is, blow it out or use a vacuum cleaner to remove the debris
4. Undo any screws, blots or clips holding the air filter cover in place and carefully lift up the cover
5. If carrying out a routine service, the element should be renewed regardless of its apparent condition
6. If you are checking the element for any other reason, inspect its lower surface; if it is oily or very dirty, renew the element. If it is only moderately dusty, it can be re-used by blowing it clean from the upper to the lower surface with compressed air. Wear protective glasses when doing this. Remember, if it is a pleated-paper type filter, it cannot be washed or re-oiled. If it cannot be cleaned satisfactorily with compressed air, discard and renew it
7. Wipe out the inside of the housing. Check that no foreign matter is visible, either in the air inlet or in the air mass meter
8. Ensure the new air filter element is correctly fitted the right way up and then replace the housing and secure all screws and any clips