How to Clean a Diesel Air Filter


Disposable paper filters for cars and trucks are being replaced by new kinds of filtration devices that can be cleaned instead of disposed of every time the filter becomes filled with debris. Diesel engines that use paper filters can benefit from a high-flow, reusable filter, like the ones that KNN Engineering offers for diesel trucks. The filters are made from cotton saturated with oil to filter out even the smallest of dirt particles. To clean a diesel air filter like this takes only a spray on cleaner and filter oil to recharge the cotton fibers inside.

Things You'll Need

  • Diesel Air Filter KNN Spray Cleaner KNN Filter Oil Waste Container Rag
  • Remove the air filter from the diesel engine compartment located in the factory air box or on the end of a KNN air intake tube. Knock out any loose materials lodged inside the filter that will fall out. Inspect the filter for damage to the mesh screen or the filtering material held within. Straighten out any dents or crimps in the filter mesh so that the filter is without major defects. Bring the filter to a container that will retain any waste fluids from the cleaning. Place the filter into the container.

  • Spray the entire filter with KNN cleaning spray and degreaser. Spray the filter element so that the spray penetrates from one side of the filter through to the other side. The spray will push the dirt and debris from inside the filter to the outside walls of the filter and eventually drain into the container holding waste fluids. As the filter is cleaned of all the dirt it will regain its original color. Stop spraying once you have removed all the debris from the fibers inside the filter.

  • Rinse the air filter using cold, low pressure water. Hold a hose to the filter at an angle and allow the water to flow through the filter. Work the water through the entire filter. It is better if you start at the top and work your way down to the bottom so that the water helps to push all the tiny dirt particles down and out of the filter. Clean diesel air filters completely so that the next time it is installed, it works as well as it did when new. Cleaning is important to get the most miles from the filter.

  • Tap the filter on the side of the container to remove excess cleaning spray and water prior to wiping down with a rag to dry. Let the filter completely air dry after cleaning. For extremely dirty and clogged diesel filters, it may be necessary to repeat the process. Always let the filter dry completely before cleaning again. Do not blow the filter with compressed air or attempt to dry the filter with a device. Allow the filter to completely air dry before oiling.

  • Oil the filter using new KNN diesel air filter oil that recharges the cotton fibers for the next filtering job. The combination of cotton fibers and oil can trap the smallest microns of dirt, adding to the performance of the diesel engine in the future. Cleaning a paper diesel air filter is impossible. Instead of a disposable filter, the better performing KNN filters for diesel engines are the ones performance people look for. After oiling install the filter back into the engine compartment inside of the air box. Tighten all air filter system parts and use until dirty again.

Tips & Warnings

  • Have a paper filter available when cleaning a reusable filter. Just in case you need to go somewhere while the filter dries, you can use the paper filter as a backup.
  • Do not over oil. Reusable filters have a balance of cotton fiber and oil to do the filtering work. Excess oil can get inside of the air intake creating a build up of fluid and dirt. Remove any extra oils by knocking on the filter before installation.

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