White Smoke From Lawn Mower: Possible Reasons & Effective Solutions

It happens a lot when you see the lawn mower white smoke then dies. It’s disappointing and people get frustrated if it happens during the mowing season.

Fret not! It may simply indicate oil spillage on the engine which has a simple fix.

However, you are in the right place to learn why you are seeing the white smoke from the lawn mower and how to solve the problem yourself. More so, you will learn how to stop a lawn mower from smoking in the future.

Keep reading!

Why Is Your Lawn Mower Blowing White Smoke?

white smoke from lawn mower

Not just your mower, any motor engine can emit white or blue smoke for numerous reasons. Luckily, you don’t need the help of an expert to figure out such problems and fix them.

I will tell you exactly when you need to take it to the repair shop later in this article.

But before fixing it, you need to know why it happens in the first place. Once you know all the possible reasons, it will be easier for you to take preventive measures.

White or blue smoke from your mower engine simply indicates burning oil. And here possible reasons why are your lawn mower white smoke and sputtering:

  • You are using the wrong oil grade/poor oil grade.
  • The crankcase is overfilled with oil.
  • Faulty breather of the crankcase.
  • There is an air leak in the crankcase.
  • Expired cylinder or any rings in there.
  • An obstacle in the breather tube.
  • Lawn mower blown head gasket
  • Engine is operating at more than a 15-degree angle.
  • For storage or oil change, if you tilt the mower engine on its side. Mowing steep heels may result in the same problem too.
  • Damaged piston rings or cylinder.
  • Pouring engine oil in excess of its capacity shown on the dipstick.

Let’s explain each of the problems more elaborately. I will explain what to do to solve or prevent these problems as well.

How To Stop A Lawn Mower From Smoking?

A smoking lawn mower does not mean the end of its lifecycle. There are plenty of fixes when the lawn mower blowing white smoke and won’t start smoothly.

As you have seen, there could be plenty of reasons for white smoke and sputtering, there are plenty of solutions as well. You need to fix that particular reasons.

So, here I have listed some fixes on each of these problems:

  • Fix The Blown/Leaking Head Gasket

You can’t fix the problem yourself. That’s why I started with this one first. This is the most serious reason why the engine is emitting white smoke which may cost you money to fix.

The head gasket seals the area where the combustion happens. You can find it in between the cylinder block and head.

You will notice a lot of smoke of any color like white, blue, or black if the head gasket breaks. Other than the smoke, you may other symptoms like a strange noise, oil leaks, and extra pressure in the crankcase.

A damaged head gasket means there is no proper sealing. Even a tiny leak in the head gasket will result in oil leak into the cylinder from the combustion chamber.

As plenty of oil will rush into the cylinder, the engine won’t most probably start. Or, it may stop running suddenly.

No matter how long you keep the engine running, the smoke won’t go away until you seal the leak. It’s very hard to fix because it’s not repairable and you must replace the gasket.

Luckily, a new head gasket is very inexpensive and you should replace the old one instead of trying to fix repair yourself.

  • Overfilling The Engine with Oil

lawn mower burning oil fix

As part of the regular maintenance of your mower, changing the mower engine oil is crucial. But for that purpose or for any other reason, if you overfill the engine with oil, you may end up having a smoking problem.

Of course, your mower needs the engine oil to function smoothly and to keep functioning for a long time. But you must ensure not to overfill it. You should not be putting in less oil than needed to.

When it comes to engine oil, keeping the optimal balance is important. Whereas less oil will result in friction from the lack of lubrication, excess oil will enter the cylinder & causes problems like emitting smoke.

Putting less oil is more damaging than overfilling it. But maintaining the optimal level is crucial.

Overfilling the engine with oil will not only result in white smoke, you may even notice the oil is coming out of the engine muffler. But don’t get too scared of it.

The easy fix to this problem is not to overfill it in the first place. Normally your lawnmower should not need more than 20 ounces’ engine oil. But fill it up with the exact amount.

Every now and then, read the user manual of your mower to remember the recommended amount of engine oil needed.

After filling the engine with oil, use a dipstick to make sure the oil level is within the optimal level as indicated in the dipstick. Remove the excess oil if it indicates any overfill.

Removing excess oil is not easy. You have to drain all the oil first, then pour the recommended amount again. That’s why it’s better to get it right the first time.

Read the manual to see whether your lawnmower has an engine with splash lubrication method or not.

If it has the splash method, the engine will splash a little amount of oil automatically on different parts of the engine to keep them lubricated. The rest of the oil will sit at the bottom of the engine.

  • Tipping The Mower/Mowing Steep Heel

Mowing the steep lawn or tipping your mower may result in oil entering the cylinder and start burning. When the oil in the cylinder starts burning, you will see the white smoke emitting.

When you replace the blades or want to have a look under the deck, you may unwittingly tip the mower to its sides. So, mowing on the steep heel and tipping over are two common reasons why the cylinder may fill up with oil.

The simple solution to this problem is to keep the engine running idly until all the oil burns up that has gotten into the cylinder.

To prevent the same problem from happening again, I must refer to the user manual of your mower. There you will find exactly how to tip over the mower or whether you can mow on the steep heel.

Unless it is not suitable to mow steep heels, you should not mow on the surface with more than a 15-degrees slope.

If you have to tip over the mower for maintenance work, you should do so by keeping the carburetor and air filter facing upwards.

Of course, this does not apply if you own a tractor mower. Then you have to figure out other kinds of reasons.

  • Damaged Piston Rings

Another common reason for having a smoking lawn mower is the failed or damaged piston rings. If you don’t maintain your mower properly and regularly or you have a really old mower, this problem is pretty much inevitable!

There are plenty of reasons why the piston rings get damaged. But the most common reason is the worn-out or dirty air filter.

The worn-out air filter can’t prevent the dust and other tiny particles from entering the combustion chamber which ultimately damages the piston rings.

Having the damaged piston ring is bad news. This is why…

Because the piston rings of your mower control the engine oil. And it supplies the required amount of oil (which is very little) to the piston to keep the moving smooth inside the cylinder.

It also removes any excess oil from the combustion chamber. So, when you got the damaged piston rings, it can’t stop the oil to enter the combustion chamber. Ultimately, it can’t prevent the burning up of the oil and the white smoke.

The reason I said having the bad piston rings is bad news because you can’t repair it yourself unless you are a professional and you have the special kind of tools required for it.

The damaged piston rings mean you have a damaged cylinder issue as well. Repairing the piston rings also means a complete engine rebuild.

If you are hell-bent on repairing it, take it to any professional repair shop. But the wisest decision would be completely replacing the engine with a brand new one!

  • Mixing Oil in 4-Stroke Mower

All the modern lawn mowers come with a 4-stroke engine. Whereas a 2-stroke mower engine can accept mixing oil in the fuel, it’s a big no for a 4-stroke engine.

If your mower has a 4-stroke engine, it means it’s more reliable and requires less maintenance than any 2-stroke mower. You don’t need to mix oil in its fuel. This is where some people make their mistakes.

Mixing the oil in the fuel for a 4-stroke engine will result in burning the oil with plenty of smoke. To make things even worse, running the engine with mixed oil will lead to damage to the engine!

By mistake, if you put the oil in the fuel engine, you can remove the oil simply by running the engine until the contaminated gas runs out. Then you can put the clean gas into the fuel tank again.

Removing oil by running the engine will result in while smoke for sure. If you want to be on the safe side and want to remove the oil without running the engine, follow the below-mentioned steps:

  1. Get a pan to collect the oil from the fuel tank.
  2. There is a fuel line connecting the fuel tank and the engine. Locate that line.
  3. Remove the fuel line from the fuel tank end. You can simply undo the clip holding the line and pull it off.
  4. Keep the pan in place to collect the oil from the tank as soon as you remove the fuel line from the tank. Make sure you don’t have any spilled gasoline scenario. It’s a serious fire hazard.
  5. Now, locate the carburetor to remove oil from there too. Locate the carburetor bowl located right underneath the carburetor.
  6. Unscrew the nut from the carburetor bowl to remove the oil from there and collect it with the pan.

Of course, there will be some leftover oil inside the carburetor bowl. I strongly recommend removing the leftover oil as well. You can find plenty of good carburetor cleaners from online stores like Amazon easily.

FYI: Do not tilt the mower while draining fuel from the tank or the carburetor bowl. It will spill the oil into the carburetor or the cylinder.

Frequently Asked Questions (FAQ)

What Does White Smoke From A Lawn Mower Mean?

Answer: It indicates either a blown head gasket of your mower or moisture in the combustion chamber. You need to replace the blown head gasket ASAP or remove the moisture from the chamber.

How Do I Fix White Smoke From My Lawn Mower?

Answer: If it’s happening due to the blown gasket, replace it immediately. But there are plenty of other reasons for the white smoke. If it’s for the spilled oil, burn off that oil.

Why Is My 4 Stroke Lawn Mower Smoking?

Answer: Most likely you have put mixed oil in the fuel tank. Remove the mixed oil from the tank and from the carburetor bowl and put clean gasoline again.

How Do I Know If My Lawnmower Has A Blown Head Gasket?

Answer: Well, if your lawnmower does not start or is dropping out and there is an oil leak, your mower has a blown head gasket issue.

Will Too Much Oil Cause White Smoke?

Answer: Yes. If you overfill the engine with oil, you will notice white smoke with grey or blue tint. Because the engine will be burning the excess oil that has entered the combustion chamber.

Why Is My John Deere Tractor Blowing White Smoke?

Answer: As per the company itself, you got nothing to worry about. It’s normal that your new John Deere tractor will be emitting white or blue smoke during the initial break-in period because it consumes oil during that period.

Sum Up

Of course, blue or white smoke from lawn mower is concerning. But as you have seen, there are plenty of easy fixes to stop a lawn mower from smoking irrespective of the color.

As long as you know the right lawn mower burning oil fix, you can take preparation for the mowing season in full swing! Share it with your friends so that they can learn what to do when there is mower white smoke and won’t start.

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