Truck Topics

The Tool Box - Changing your Air Filter

The air filter is probably the most forgotten filter, but one of the most important. Your engine needs clear air to run its best. The air filter in most cases cannot be looked at to tell if it is dirty. On some trucks there is a restriction indicator: when this filter is really dirty it locks in on red; otherwise its green. I believe you should change the air filter before it gets that dirty, so I change mine every 75,000 miles.

Changing your Air Filter too often can be just as bad as not often enough. The media in filters, when new, allows very fine dust through until it “seals” the element. This can take from 3000 to 5000 miles. So changing too often allows fine dust into your engine.

To find your air filter look for a large, black (in most cases) metal or plastic housing. Some have lids that have snap-over clips that require no tools. To remove, just flip the clips remove the lid and there is the filter. Grab the filter, wiggle it a bit if it is stuck, and pull it out. Install new filter, reinstall the lid and snap over the clips and it is done.

Other trucks like the M2 Freightliner have a filter that the hood seats into with a rubber boot. It uses 3 screws to hold the filter element into place. Using a flat or a Phillips screwdriver remove the screws (new ones will come with the new filter) grab the lip of the filter, wiggle it some (it will be stuck) and lift it out of housing. Drop new filter into housing (lining up screws with nuts on housing) push filter into housing screw it in a little at a time until the filter is seated around outside edge, and you are done.

Trucks with external air cleaners use nuts and bolts to hold the lid on the housing. Just remove the nuts, remove lid, and remove the air filter. Install new filter, reinstall lid and new gasket (if supplied) reinstall nuts, tightening them a little bit at a time until tight. Repeat on the other side if you have two air filters.

Some people believe that an air filter can be cleaned by blowing air backwards through the air filter. This can actually cause damage to the filter. If reinstalled the engine could be damaged because filter has been damaged and allows more dirt into motor. I believe if you take the filter out you need to replace it as you have broken the seal between the element and the housing.

The cab air filter is also one of the filters that doesn’t get changed as often as it should. Check in your owner’s manual to find it. Manufacturers seem to like to hide this filter within the truck. The M-2 cab filter is behind the panel in front of the passenger seat. It takes a Torx bit to remove the three screws holding the panel on a 5/16" socket (should be in your 3/8" drive socket set) to access the filter. Remove the filter, install new filter, reinstall the cover with a new gasket (included with filter), reinstall screws, reinstall panel and you’re breathing clean air just like your truck.

If you can’t find your cab air filter, ask next time you go into a shop. Until next time breathe easy!