Why is My Lawn Mower Blowing White Smoke?

White smoke coming from the lawnmower can be dangerous and inefficient at the same time. But what will you do when a big cloud of smoke induces from inside your mower? Scary right? Well, almost everyone asks this “why is my lawn mower blowing white smoke” question once in a while.  

A lawnmower may burst out in smoke for several reasons. Air leaks, overfilling the crankcase, poor grades of oil, etc., are just the tip of the iceberg. 

This article will see how you can find out the smoke causes and fix it with ease. So, let us begin.

Cause of white smoke from lawn mowers

Scary as it may seem, but all machines have problems lurking inside their parts. In the case of a lawnmower, the following mechanical problems are the most common. 

Crankcase Problems

A crankcase is a casing, which covers a crankshaft or encloses it. In other words, the crankcase provides housing for the mower’s internal combustion engine. Problems inside the crankcase may lead to blowing white smoke from the mower. The most common crankcase problems are,


Overfilling the mower engine causes oil issues. If you add too much oil to the lawnmower, the symptoms may take a little time to appear. But once it does, the results are pretty. You may find oil pouring from the tank or even white combustion smoke. 

A lawnmower engine is not for pouring too much oil as a reserve. So, submerging it in oil is a major cause of your problem. 

Air leak

Air leaks in engines cause engine misfiring, performance issues, overheating, and many other problems. If you don’t solve the air leak problem, your engine will show signs of white smoke. 

Why is My Lawn Mower Blowing White Smoke?

The symptoms of air leaks are often seen when you overfill your oil tank regularly. Overall, you will get reduced acceleration and power during mowing. 

Breather blockage in the crankcase

When you operate a lawnmower engine, the suction of air pulls gases out of the crankcase. So, to stop this type of vacuum, a breather comes into use. 

Yes. The part located in the oil cap is the breather. 

Blockage in the breather doesn’t allow proper air fluctuation. After a while, an internal pressure inside the engine generates and makes white smoke appear. 

Poor oil quality

When you use low-quality oil, your lawn mower engine may face some serious consequences. First, oil consumption will escalate and cause some costly engine repairs. Then again, your warranty may get void for using low-quality engine oil. 

Getting white smoke is also an issue as the engine can process the oil properly. 

Worn out Cylinder

A lawnmower can last for years with proper care and regular usage. However, nothing lasts forever, especially if it’s an oil engine. With regular use, you put pressure on the cylinder, and after several years, the cylinder gets worn out. 

An aged-out cylinder will produce white smoke no matter what. Replacing the cylinder will do the trick, and you don’t have to worry about any combustion smoke. 

Broken head gasket

A head gasket is a part of the mower between the cylinder head and the block. Though rare, you may still find yourself with a broken gasket. Symptoms of broken gaskets range from oil leaks, internal pressure increase, strange noise, and white smoke. 

The only way you can replace it is by replacing it with a proper head gasket. 

Fixing white smoke issues from Lawnmowers

To fix the smoking problem, first, you need to diagnose the cause of the problem. In most cases, the problem occurs due to overfilling. As a precaution, don’t overfill. 

Get to know your engine better. Search for leaks. Try finding any oil leaks, air leaks, and check the oil quality. 50% of the time, poor oil quality makes up for the white smoke emission from the mower. You can also check for a blocked breather. 

After the diagnosis procedure, we can move on to the fixing part. 

It is better to replace any part as the head gasket, cylinder, etc., rather than fixing it. Open the lower engine and look for any leakage, fix it a leak fixer. 

If any methods don’t work, you may have to replace the head gasket. For this step, try finding professional help, as the condition is rare and normal fixes can’t help. 

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How much does it cost to fix a blown head gasket on a lawnmower?

The price of a head gasket on a lawnmower depends on the brand and model of the mower. You can get a decent deal on a head gasket starting from 1200 to 3000 dollars max. 

What happens if you put too much oil in your lawnmower?

Putting too much oil in your lawnmower or any other machine is damaging. For starters, the mower engine can get oil leakage, and white smoke may appear, and so on. 

What causes oil to come out of your lawn mower?

When the lower bearing ring seal gets damaged, you will find direct oil leakage. Overfilling the mower with oil is a leading cause of oil leakage. So, to prevent it, don’t overfill. 

Can a lawn mower explode?

Yes. But the incidents are pretty low. The only way your lawn mower can explode is through catching fire combined with an overfilled tank. 

Is white smoke dangerous?

All types of smoke are harmful to the body. Black or white, smoking causes lung disease, trouble breathing, and even Carbon-mono-oxide poisoning. So, yeah. It is deadly. 


Why is my lawn mower blowing white smoke? When you ask this question, the condition is always bad. However, fixes are easy to find. With white smoking lawnmowers, the fix is usually simple. 

If you have any problem finding a solution, just let me know. Read the article once more, and keep in mind not to overfill once you fix the problem. 

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