Auto Repair: Air Filter Maintenance

Servicemember auto engine repair.

Maintaining Your Air Filter

On most modern vehicles, the air filter is under the hood inside a rectangular cold air collector box that's located up near the front of the engine compartment. Figure 8-1 shows you what it looks like. (Other vehicles, including thosewith carburetors, have big round metal air cleaners that are hard to miss.)

As you can see in Figure 8-1, the air cleaner has a large air inlet duct (also called the air intake hose) connected to it. Loosen the hose clamp that seals it to the box, and then undo all the screws, clamps, or wing nuts that hold the lid of the box in place. Put the fasteners you removed somewhere safe so that they don't roll off into oblivion. Open the lid of the box and . . . voila! . . . you should find the air filter inside (see Figure 8-1). Lift out the old filter (it isn'tfastened down) and take a look at it.

Figure 8-1: The cold air collector box houses the air filter.

Some older vehicles have permanent air filters, and some off-road vehicles have more-complex filters with wet and dry elements. Clean and replace these according to the instructions in your owner's manual. If you don't find a pleated paper, cotton, or gauze filter inside your air cleaner, you probablyhave one of these alternatives.

Checking and Cleaning Your Air Filter and Cold Air Collector Box

To figure out whether your air filter needs to be replaced, just hold it up to the sun or to a strong light. Can you see the light streaming through it? If not, try dropping it lightly, bottom side down, on a hard surface. Doing so should jar some dirt loose. If the filter is still too dirty to see through after you've dropped it a few times and it looks as though it just needs a bit of cleaning, you can try to clean it following the directions below. If that doesn't work,you need a new one.

Caution: To clean a pleated air filter either use an air hose to blow the dirt off (not through) it or a vacuum to suck it out. For both methods, handle the filter gently to avoid crushing the pleats. Keep the nozzle of the air hose or vacuum cleaner several inches away from the filter — don't jam it up against it. And if you're using compressed air, do it away from the vehicle to avoid blowing thedirt around under the hood.

If the interior of the box is fouled with dust or sand, before you clean the box paste some duct tape over the open end of the air intake hose so that the dirt can't get in. Then either use the compressed air hose to blow the dirt out ofthe box or the vacuum cleaner to suck it out.

Tip: I prefer a "hand vac" for this job. You don't have to buy a compressed air gun or schlep the car to a service station to use theirs (and some of them are now charging for the air!). Also, with a hand vac, you run less risk of blowing the dirty air out of the cold air collector box and into something else. I keep a battery-powered hand vac in the trunk of my car to do stuff like this as wellas to get the dirt off the floor mats and to clean the upholstery.

Buying and Replacing an Air Filter

Because the air filter extracts dirt and dust particles from the air, you should change it at least once a year or every 20,000 miles, whichever comes first — unless yours gets very dirty before then. If you do most of your driving in a dusty or sandy area, you may need to replace your air filter every 5,000 miles or less. If a road trip takes you to such an area, it's a good idea to check theair filter right after you return.

When buying an air filter, keep the following points in mind:

  • Look for well-known, quality-brand filters, especially if you're buying at discount stores. Unknown brands sell for very little, but they aren't always of good quality, and if your air filter lets a lot of junk get into your fuel system, you may find that the cheap filter is very costly in the long run.
  • If you need help determining which air filter you need, go to your local auto supply store or to the parts department at your dealership. Give them your vehicle's make, model, and year, and they'll select the right part number for your vehicle.
  • To save yourself a trip back to the auto supply store, take the time to open your cold air collector box and check the filter you purchase against your current filter while you're still in the store parking lot.

    Make sure that the filter you get matches your old filter in size and shape. It should look exactly like the old one. If it doesn't, you've bought the wrong filter. If the new filter looks right, replace the old filter with the new one, making sure that the rubber rim is facing up to create a sealbetween the filter and the box.

When the cleaned filter — or the new one — is in place, put the lid back on the box and replace all the stuff that held it on. Then, remove the duct tape from the open end of the air intake hose and use the hose clamp to reattachit to the box. Done!

From Auto Repair for Dummies, copyright © 2009 by Wiley Publishing, Inc., Indianapolis, Indiana. Used by arrangement with John Wiley & Sons, Inc.

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