Lawn Mower Blowing White Smoke – What To Do?

We may get commissions for purchases made through links in this post.

If your lawn mower begins to blow white smoke, the chances are that something is going on with the lawn mower’s engine. But what types of problems will cause this type of issue? We have looked into the most common reasons for this. In this post, we will discuss how they can be fixed and potentially prevented.

Here are common reasons why a lawn mower may blow white smoke:

  • Worn piston rings
  • Too much motor oil
  • A damaged or worn head gasket 
  • The mower has tipped over
  • A faulty carburetor seal

If you notice that your lawn mower is blowing white smoke, it’s best to turn off the motor and repair the issue before continuing to use it. You may be able to repair some issues on your own by simply replacing a part or fixing a damaged component. However, for more advanced issues, it may be best to purchase a new mower entirely. Continue reading to learn more about the most common reasons why a lawn mower might blow white smoke.

A lawn mower placed on the garden, Lawn Mower Blowing White Smoke - What To Do?

Reasons Why A Lawn Mower May Blow White Smoke

A man using a lawn mower to straighten his lawn

Worn piston rings

Worn piston rings are probably one of the most common reasons for a smoking lawn mower. Piston rings create a seal between the cylinder wall of the motor’s engine and the piston. When this seal breaks due to wear and tear or damage, the oil will leak past the piston rings and into the combustion chamber. And when this happens, white smoke will come from the engine. If your lawnmower is low on fuel, needs a filter change, or has cylinder issues, these reasons can also cause smoke to appear from the piston ring. 

You may be able to replace the piston ring yourself in under 30 minutes, depending on the type of lawn mower that you have. However, it is important to know that doing so will require special tools and advanced knowledge of the motor’s engine and components. If you’ve never worked on any type of engine before, the job may be too complex to tackle on your own. In which case, it’s probably best to take the lawn mower to a repair shop.

Take a look at this Power Smart lawn mower on Amazon.

Too much motor oil

Most lawn mowers only need a little over half a liter of motor oil. It’s common to assume that pouring extra oil into the motor will not harm. This couldn’t be further from the truth! Overfilling your lawn mower with oil can cause the oil levels to rise higher than the paddles, which help to keep the engine running. When this happens, you will notice white smoke coming from the engine as it tries to burn off the oil.

The quickest way to fix this is to simply drain the oil completely and allow the engine to run until the smoke dissipates. If you still notice white smoke coming from the motor after the oil has burned, you may need to clean the carburetor.

Learn more about this 4-cycle motor oil.

A damaged or worn head gasket 

Another common reason why your lawn mower may blow white smoke is a worn or damaged head gasket. The head gasket of a lawn mower is used to seal the engine so that it’s closed off from the rest of the components. If the head gasket becomes damaged, the oil will begin to leak from the crankcase into the cylinder; this will cause white smoke to rise from the engine as it works to burn it off.

A faulty head gasket is a fairly serious issue, and it should be addressed immediately. If not, it could cause permanent damage to the engine. You don’t want the oil to be sucked into the combustion chamber by way of the gasket, as it could cause the engine to shut down completely.

The fix for this issue is really simple. You’ll need to install a new head gasket in the lawn mower. The good thing is that head gaskets aren’t that expensive, and you can get a new one for under $20. If you happen to have an old mower lying around, you may be able to use its head gasket for your new mower if it is still in good condition–that is if the mower has the same engine size.

The mower has tipped over

If your lawn mower has ever tipped over, you may have seen white smoke blowing from its engine. In which case, it is usually a temporary and pretty easy problem to fix. It’s important to know that your lawn mower should not be tipped at an angle over 15 degrees, as it can cause the oil to leak into other areas of the engine. In this case, it causes the oil to leak from the crankcase into the cylinders. However, this is a common occurrence that happens when you are removing, storing, or cleaning your lawn mower.
 
The first thing that you should do when this occurs is to stand the lawn mower upright and check the crankcase to determine if the oil needs to be replenished. If it does, add more oil to the fill level. Next, let the motor run until the smoke completely dissipates. 

A faulty carburetor seal

If the carburetor seal on your lawn mower fails, you will likely notice the smell of gas when you start the engine. This can often occur if the oil level is beyond the recommended amount or if the carburetor is clogged with dirt or grime. In some cases, you may be able to clean and re-fit the carburetor, and in other scenarios, you may need to replace it completely.

Lawn mower carburetors can be cleaned in about 15 to 20 minutes. It’s important, however, to have your user’s guide handy so that you’re able to properly rebuild the carburetor when it’s time to re-attach it to the engine. If you’d prefer not to clean the carburetor yourself, you can buy a new one for around $15 to $20 at your local hardware store or online.

How do I know if my lawn mower has a blown head gasket?

A checking his lawn mower before starting it

When a lawn mower blows a head gasket, it will quickly give off SOS signals that’ll help you diagnose its current state. Let’s take a look at the three most common signs.

Smoke comes from the exhaust

When black or white smoke begins to float up from the exhaust of your lawn mower, it is usually the result of a blown head gasket, which may indicate issues with the mower’s combustion system. Worn or damaged gaskets are easy to replace and should be attended to immediately to prevent further issues.

The motor constantly shuts off

A faulty head gasket can cause the mower to drop out and shut off randomly. This may be common when you turn a corner with the mower. It’s often the result of a worn or damaged gasket causing low pressure in the motor’s combustion chamber. In which case, the gasket will need to be replaced.

The engine keeps leaking oil

Another sign of a blown head gasket is when the engine constantly leaks oil. If you find that you are refilling the oil in your motor more frequently than normal, the chances are that it is leaking from the damaged gasket. You can check the gasket to see if there is wet or dried oil around the edges. If there is, the gasket will need to be switched out for a new one.

How often do you change the oil in a lawnmower?

Most lawn mower manufacturers recommend changing the oil in a lawn mower every 20 to 50 hours of work. The oil and chamber filters should be replaced once or twice a season, depending on how often you use your lawn mower. 

Is it worth repairing a lawn mower?

Just as with any other appliance, the best way to determine if your lawn mower is worth repairing is to determine its current value and compare it to the cost of the repair. For example, if you have a lawn mower that is at least five years old and has issues with its transmission or crankshaft, it may not be worth repairing at all. 

What is the lifespan of a lawnmower?

On average, most lawn mowers will last anywhere from 5 to 10 years. Proper care and maintenance can help extend the lifespan of your lawn mower and reduce potential repairs.

Wrapping Things Up

Remember, if you notice that your lawn mower is blowing white smoke, turn it off immediately and try to troubleshoot the issue. White smoke doesn’t mean that the lawn mower is broken, but it may need a bit of TLC. 

Before you go, be sure to check out some of our other posts:

Can You Over Fertilize A Lawn?

11 Perennial Ryegrass Facts For Lawn Owners

Leave a Reply