Before servicing air filters, turn the ignition off and wipe the dust from the cover and surrounding surfaces. When removing the filter element, don't jar or bump it as this could cause dirt to fall into the engine intake. Use a clean, moist cloth to wipe out the housing. Wipe toward the engine inlet opening, and wipe the gasket sealing surface on the housing making sure it's smooth and clean.
If the filter has an inner element, leave it in place while servicing the primary element. Inspect it for concentrations of dust, which may signal leaks in the gaskets or media of the primary filter. Normally the inner element needs to be changed only every third to fifth time that the primary element is changed. If the equipment has a pre-cleaner, remove, empty and clean any collector bowls, dust cups or unloaders. If there are evacuation tubes connected to the exhaust, clean them with a stiff brush or compressed air.
Then, before you install your new filter, check the part number to ensure it matches the old filter. Also, inspect the new filter to verify it is not damaged. Don't use any replacement filter that shows damage or doesn't fit quite right. After installing the filter, inspect the cover sealing gasket and replace it if necessary. Tighten all clamps or bolts on the cover in diagonal order and check to see that the cover is seated uniformly. Inspect the air induction line. Then tighten clamps and connectors and replace any rubber connectors that are cracked.
Before discarding the old filter, be sure to inspect the old filter for damage and other telltale signs that could help you solve potential future problems. Some things to look for include:
Soot. An accumulation of black, oily soot can indicate the air intake is located too close to the exhaust. Consider relocating it.
Dirt. An accumulation of dirt on the clean side of the element may indicate a split in the filter media. Also check to see if the end-seal is being by passed or if there is gasket leak. Do not attempt to reuse it if this is the case.
Rust. If metal parts of the filter are rusty, this can indicate water is being drawn in with the air. Check the intake location and make sure water venting ports in the induction system are not clogged.