Fresh air

| August 07, 2007

Maintain your air cleaner to keep your engine running better, longer.

One of the most important discoveries early engine designers made was that engines would last much longer if the intake air was cleaned. Dust in that air ended up in the oil, where it formed a potent grinding compound that ruined entire engines – and it still can.

The air cleaner has a lot of air to clean. A Caterpillar C15 engine at 1,500 rpm, even under light-load cruise conditions with little turbo boost, will fill the entire volume of its cylinders (928 cubic inches) with a fresh batch of air at least 12.5 times a second. The engine at this rpm will use more than 6.7 cubic feet of air per second. When accelerating or hill climbing with high boost pressures at this rpm, it will ingest air more than twice as fast as that. And all that air has to be at least 99.9 percent clear of dust. That’s why maintaining your air cleaner and the associated intake piping is so important.

At Hunter Keystone Peterbilt in Lancaster, Pa., Service Manager Ray Jakubus and shop Formean Dave Brown know how to service several different types of air cleaners.

Single or duals
Many modern aerodynamic trucks have a single air cleaner mounted under the hood. These can be quite easy to service but may not offer a lot of capacity for dirt. Older, more classically styled trucks often have dual chrome or stainless air cleaners situated on either side of the cowl. These offer a much larger volume of space for the air cleaner cartridge. By having two units plumbed to supply equal amounts of air to the engine, they don’t have to be so frequently serviced.

Another advantage of dual cleaners is low restriction. The air cleaners take a very long time to clog with dirt, and the lower the restriction, the better a late model engine will perform and the better the fuel economy will be.

Precautions for maintenance
Careless air cleaner maintenance can actually increase engine wear.

First of all, the engine must always be shut off throughout the procedure. The keys should be removed so no one can start the engine accidentally. Not only will a running engine draw in dust that will tend to accelerate wear, there is a good chance an object like a rag near the air cleaner could be sucked into the air intake and become very difficult to remove.

Precautions should also be taken throughout the procedure to prevent dust anywhere on or inside the housing from being allowed to enter the intake piping downstream of the filter cartridge. Wipe off the outer housing where the cap or other covers will be removed. Also to be sure to wipe off any dust that may fall off the filter cartridge into the air cleaner housing or associated piping before replacing the cartridge and closing the housing back up.

It is also important throughout the procedure to inspect all seals and hoses for leakage of any kind.

Doing the job
On a traditional Pete 388 with external dual chrome air cleaners (A) and a Cummins ISX engine, one of the most effective ways to judge when it’s time to service an air cleaner is by checking the restriction gauge. On this truck (B) the gauge is dashboard mounted. Brown says the air cleaners on this model have so much capacity you’d probably be smart to replace them when the restriction gets about 3/4 of the way to the red line. With this type of gauge, you need to read the restriction when the engine’s airflow is at the maximum – that is, when under maximum load and running at maximum rpm.

The reason for replacing the cartridges early is that they last so long their seals or filter medium can deteriorate even before the filter is clogged. Leaking seals or a defective medium can let a lot of dust in.

In fact, it’s ideal to remove and inspect air cleaners at every major maintenance interval – every second or third oil change, Brown says. This ensures problems will be corrected before significant damage is done.

Some trucks will have a different type of restriction gauge, located under the hood (C). This gauge will record the maximum restriction so you can read it when the engine is off. If the slot on the side is entirely red, the air cleaner needs servicing. The slot will have both yellow and red in it when approaching maximum allowable restriction, indicating the need to service the unit soon.

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