Running a Lawn Mower Without an Air Filter: All You Need To Know


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Lawnmowers come in contact with all kinds of dirt and debris when you use them. The air filter helps keep this dirt out of your mower, allowing it to stay and run clean. However, how important is the air filter to a lawn mower’s overall functionality?

Running your lawn mower without an air filter can be harmful to your engine as it will begin to fill with dirt and debris. This can cause the engine to be less effective and even stop working altogether. You should clean or replace your air filter regularly. 

Let’s talk more about the importance of a lawn mower air filter and why you need it for the mower to run smoothly. 

What Happens If You Use Your Lawn Mower Without an Air Filter?

Without an air filter, your lawn mower will not have a way to stop dirt and debris from getting to the engine. So, there’s a good chance that not using an air filter even once can damage your lawn mower and even make it unusable. Let’s get into specifics about how this can affect your mower. 

Reduced Engine Life

First, it’s important to know that running your lawn mower without an air filter will reduce the longevity of your engine. The dirt and debris that an air filter would typically block now have access to the mower engine. This will shorten the lifespan of the component, leaving you to replace it sooner than you would otherwise need to. 

This is an ongoing issue that you may not initially notice or experience. However, it can have long-term negative effects. If you leave the debris inside the engine, the engine may stop working altogether or, at the very least, require some costly repairs.

Overheating

Lawnmower engines work effectively when they are properly lubricated. Dirt and other impurities entering the engine can reduce the amount of oil that flows through it, which keeps it from overheating. Without enough oil, moving parts of the engine can cause friction which causes the engine to overheat. 

Even if enough oil is present so that the debris doesn’t cause friction, overheating can still occur if the debris blocks the cooling fins. These fins help move heat away from the engine to prevent overheating. With debris blocking the cooling fins, your engine has a much greater risk of overheating as the warm air will not circulate out of the engine. 

Overheating in your lawn mower engine can also happen because the component needs to work harder to move around debris. If debris gets into the engine or the lawn mower’s blades, they will need to use even more power to work around the particles. The harder the engine needs to work, the more likely it is to overheat. 

Affects Engine Speed

Another problem you’re likely to face without an air filter is a slower engine speed. This may be difficult to notice initially, but it can become a much bigger issue as time goes on. Slower engine speed can happen due to the lawn mower trying to work around engine debris or even a dirty carburetor. 

If you notice issues with attempting to increase the throttle, this is often indicative of a dirty carburetor. Carburetors combine air and gas to allow the lawn mower to run smoothly and use the right amount of fuel. They’re part of your lawn mower’s engine, so the air filter also protects them from harm. 

While a dirty carburetor may still allow your lawn mower to start, you will notice that it takes more starting attempts than normal. It can also cause the engine to cut off while in use or cause the engine to run very roughly. Your lawn mower may also run through a lot more fuel than normal because of a clogged or dirty carburetor. 

How To Replace a Lawn Mower Air Filter

Now that you know the importance of an air filter, let’s talk about how to replace yours. First, you need to make sure you purchase the correct air filter for your lawn mower. Otherwise, it may not fit properly, or it may clog quickly. Check your owner’s manual to see exactly which type of air filter your lawn mower requires, as options vary based on brand, size, and overall model. 

Safety First

Before doing any work on your lawn mower, I highly recommend disconnecting the spark plug and battery cables. This is similar to turning the power off in a room before messing with electrical equipment. It will ensure that you’re safe while working on your lawn mower and allow you to remove and unscrew parts as needed without the risk of sparking or injury. 

Additionally, you should wear eye protection, older clothes, and gloves. Not only are lawnmowers especially dirty, but they can hold and carry things like poison ivy and other irritants. So, protect your eyes and skin as much as possible when working on your lawn mower, and never work on a mower when the engine is running. 

If you want some more information on keeping yourself safe while working on your lawn mower, as well as other essential tips for maintenance, check out my article How (and how often) to Service a Lawn Mower. It features some other parts of the lawn mower that you need to regularly perform maintenance on, including how to remove debris from other parts of the mower besides the air filter. 

Remove the Old Air Filter

To get to the air filter and replace it, you will need to remove the section of the lawn mower that houses the component. To do this, you will need to remove the retaining bolt. You can do this pretty easily with a flathead screwdriver. 

Once you remove the bolt, you can remove the air filter housing unit. The housing unit is comprised of two parts that hold the air filter in the center. Once you remove them from the mower, you can easily slide the air filter from between them. 

Clean the Housing Unit Before Inserting New Filter

Once you remove the old air filter, clean the housing unit before adding the new one. This will ensure that your new filter lasts as long as possible and doesn’t clog or cause issues later on. You can do this with your hands or by using a brush if you want a deeper clean. Remember, the cleaner you get the housing unit, the better off your filter will be. 

Don’t clean the housing unit with any liquids, as they can damage it. So, scrub it with a dry cloth or dry brush carefully to ensure you remove all debris. These filters can get pretty dirty over time, so, you may get dirty doing this as well. Prepare by wearing old clothes, gloves, and even a face mask if you want to be extra careful to avoid ingesting dirt and particles. 

Consider Cleaning the Old Filter

If your lawn mower air filter is dirty but doesn’t look like it needs replacing yet, try cleaning the old filter before inserting a new one. The filter has paper pleats on the inside that will tell you whether it needs replacing or cleaning. If the pleats are not very dirty, then you can simply clean the filter rather than replace it with a new one. 

Any discoloration in the pleats is a surefire sign that you need to replace the component rather than clean it. Otherwise, try to knock some of the dirt loose in the filter and determine if it is worth saving. 

If the mower has foam filters, you may not have the luxury of inspecting the cardboard pleats inside. If this is the case, look at the foam filter to determine if it needs replacing or if you can salvage it. The choice is up to you, but any filter you put back in your lawn mower should be completely clean. 

If you want to clean the filter, how you do it depends on the type you have. Filters with cardboard pleated inserts should not get wet. So, simply knock these filters on a hard surface to dislodge the extra dirt and wipe them clean with a dry rag. 

For foam filters, you can wash these in warm water with gentle soap. Use a mild soap that also fights grease to help with troublesome dirt and debris in the filter. Once cleaned, place the foam filter somewhere warm and allow it to dry completely before putting it back in the housing unit. 

Prepare the New Filter Before Putting It In

It’s far more likely that your filter needs replacing rather than just a cleaning. Whether that’s the case or you just want to play it safe, dispose of the old filter and clean the housing unit. Foam filters are more likely to allow cleaning and reuse than paper filters. However, it’s still important to replace those foam filters once they are beyond cleaning and reusing. 

Before placing your new filter in the housing unit, check the owner’s manual or the air filter instructions. Some filters need oil added before you can put them in, while some others can go in dry. The process will differ based on your lawn mower and the filter you put in. So, check the directions in the owner’s manual carefully. 

If you need to add oil, do this carefully so as not to oversaturate the filter. Remember, too much oil can cause the air filter to clog, but not using oil when you need to can cause the air filter to be ineffective, which is why you want to strike a delicate balance.

Replace the Housing Unit

Once you add the new or clean filter, ensure it’s completely in the housing unit before closing everything up. If you have the wrong type of filter, you will probably figure it out during this stage, as the housing units leave very little room for mistakes. If it fits, it’s time to close up the housing unit and start the lawn mower. 

Starting the lawn mower immediately after replacing the filter will allow you to note any negative changes in how it runs and fix them before they turn into a larger issue. If you used the correct filter and followed the oil directions carefully, then your mower should be running smoothly. 

How Often You Should Change a Lawn Mower Air Filter

In order to keep your lawn mower running smoothly, you should replace the air filter in your lawn mower about every three months. Changing it about once every summer or season is a reasonable frequency, but it also depends on how much you use it. 

The air filter on a lawn mower catches all the dirt and debris before it can reach your engine. So, there can be a lot of impurities that clog it or get stuck in it. Replacing it every few months is reasonable for those who use their lawn mower regularly just for their own yard. 

The filter may need to be changed more often for landscapers or people who mow other lawns besides their own. Ultimately, it depends on how much you use the equipment. If you notice that your lawn mower is not running as smoothly as it should, it may be time to change the filter. In fact, you may need to set a reminder to change it more often so these issues don’t happen again.

Final Thoughts

Without an air filter, your lawn mower is at high risk of a clogged engine, which often requires costly repairs. Never run your mower without an air filter to prevent this and other issues from occurring. 

I’ve provided some helpful tips above for keeping your air filter clean or replacing it if you need to. Just remember to always check the owner’s manual to find the correct filter first to prevent needing to return it or spending even more money to fix the mower. 

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Lars

I am always happy to share all my knowledge about how to keep your garden in good condition and make it special.

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