How To Clean and Replace a Walk-Behind Lawn Mower Air Filter

Updated: May 19, 2023

Want to keep your walk-behind mower in good working order? It pays to know how to clean or replace your lawn mower air filter.

Just last week, I got a call from my father-in-law in Poland requesting lawn mower advice. For the last 12 years or so, he’s used the same walk-behind mower in his suburban yard near Warsaw. The machine worked fine until this spring, when it suddenly wouldn’t start.

Diagnosing the problem over Skype through a language barrier wasn’t easy, but I eventually walked him through how to check the air filter. Turns out it was completely clogged with dirt and dust and beyond cleaning, so I explained in my limited Polish that he needed to buy and install a new one.

A few days later, he did just that. Now, he tells me, the mower runs just fine.

Want to avoid unnecessary delays in your mowing schedule? Keep reading to learn how to check, clean and replace your walk-behind lawn mower air filter.

How To Check the Lawn Mower Air Filter

If you’ve been using a walk-behind mower for a while without much maintenance, chances are it’s overdue for an air filter cleaning, and perhaps even a replacement. Most manufacturers recommend replacing your air filter at least once per mowing season. This also applies to riding mower air filters.

In practice, I find I can usually get at least two mowing seasons out of a filter as long as I keep it clean. Either way, you’ll need to check the filter at least once a year. Here’s how to find and check your lawn mower air filter if you’ve never done it before:

  • Disconnect the spark plug wire from the plug to make sure your mower can’t start accidentally.
  • Find the plastic air filter housing. Look for a rectangular plastic cover on one side of the engine. Most mowers I’ve worked on have it on the left.
  • Remove the cover, then carefully pull out the rectangular pleated paper air filter.
  • Examine the filter for dust, dirt and discoloration.

What To Do If the Air Filter Is Dirty

The pleated, paper-like material on most push mower air filters is white or light blue when new. A little discoloration is normal. But if your filter is caked with enough dust and dirt to change the color and shed particles as you move it around, it needs cleaning, and possibly replacement.

For extremely dirty filters, cleaning is hardly worth the effort since new lawn mower air filters are so cheap.

How To Clean a Lawn Mower Air Filter

If you decide to clean the filter rather than replace it, you’ll need a portable air compressor with a hose and spray nozzle attachment. Here’s what to do next:

  • Remove the air filter, following the instructions above.
  • Lightly tap the filter against a solid object or surface to shake loose the dirt and dust.
  • Take your air compressor and blow the rest of the dirt and dust off the filter. Be thorough. Make sure you blow compressed air over all sides of the filter and between all the pleats.
  • Replace the filter and put the protective plastic cover back on.
  • Reconnect the spark plug wire.

How To Replace a Lawn Mower Air Filter

  • Remove the dirty filter.
  • Place the new filter into the housing, facing the same way as the old one.
  • Replace the plastic filter cover, then reconnect the spark plug wire.

Where To Buy Replacement Lawn Mower Air Filters

Whenever I need to buy a new lawn mower air filter, I do a search on Amazon that looks like this: “Toro push lawn mower 21445 air filter.” Most times I find a filter with the name of my mower somewhere in the product description, so I know it’s compatible. That’s important, since filters aren’t usually interchangeable from one machine to the next.