It was time to change the air cleaner, so a new owner-operator told the shop to go ahead and put one in. They charged him X number of dollars for the cleaner element-fair enough-but also billed him $25 to change it. “Okay, now I know,” he said. “Next time I’ll do it myself!”

Is that you? Twenty-five bucks may seem like a lot to change an air filter element, but if it took the guy a half-hour and the shop’s rate is $50, well …

Of course, it should only take a few minutes just to change out the element, and it is one of the easiest things to do on the truck. Sure, do it yourself, but remember that there’s more to it than just changing the element.

First, make sure the element actually needs changing. You can’t look at an element and say, “Yeah, it’s dirty!” It may look dirty but have plenty of life left. Changing it would be a waste.

The only way to know for sure is by looking at the air restriction gauge. Most diesel-powered trucks now have them, mounted in the instrument panel or under the hood, in the piping just downstream of the filter canister. Usually it’s a bar-type readout that shows restriction in inches (of water); as it approaches 20 inches for four-stroke turbocharged diesels, dirt begins plugging up the element and restriction on breathing will hurt fuel economy. This is a good time to change it. Color coding may also be used in the gauge, and red’s a giveaway.

The air cleaner canister can be outside the hood (on the right side or both sides of “large car” conventionals) or under the hood (on aero conventionals). On cabovers, the canister will be atop the engine (with frontal air intake systems) or behind the cab (in a snorkel system).

The element is inside the canister. Most elements today are complex designs made of specially formed and treated paper, called the “media.” Usually these are not reusable and you certainly shouldn’t try to wash them yourself and reuse them (unless your name is Cheap Charlie).

Above all, you have to be careful not to “dust” the engine. This is allowing dirt from the canister to drop into the intake pipe. From there, dirt particles can be ingested into the engine and damage things in the cylinders. A diesel needs super-clean air, much more so than a gasoline engine.

To avoid dusting, understand how the element works. There are square- and round-shaped elements, though the round ones are much more common.

Some round types bring in air from outside the element’s wall and send it on from inside the wall; others bring in air from top or bottom and send it from inside the wall through the media to the outside, and then into the engine.

Each type will deposit loose dust in a different place in the canister. You need to vacuum or carefully wipe up the dust with a damp cloth; avoid letting the dust drop into piping beyond the canister. If some falls inside, vacuum it out.

Before installing the new element, inspect its seals for possible damage. If seals are dented or split, take it back and get a new one that’s undamaged. Carefully place the element in the canister. Does it fit? If not, it’s probably not the right one for this application. Back to the parts counter with you!

Once the proper element’s installed, replace the cover and tighten it down. Some nuts may have to be torqued to certain specs. Check your manual.

There’s more to servicing the air intake system than changing the element. Moisture can also enter the engine though damaged piping downstream of the filter. So as part of the filter servicing, inspect piping and hoses for integrity, and fix anything that looks loose or damaged.

Look at the water separating mechanism-a specially formed or molded trap that strips water from inlet air-for proper alignment and operation. This will be near the air intake, which of course will vary with the vehicle. Among other things, the water separator may be loose, jostled, or its drain holes plugged.

Now, if the service technician at that shop has done all this, you might begin to understand why there’s a $25 charge for installing the element.

Still want to do it yourself?