Lawn Mower: White Smoke then Dies

Is a mysterious white smoke emerging from your lawn mower? If so, you’re probably worried and wondering what on earth is going on. If your lawn mower blows white smoke then dies, there’s even more cause for concern. In this article, you will learn about the potential causes of white smoke in a lawn mower, and what you can do to address the issue.

Let’s get started with your first burning question – is this serious and/or dangerous?

White Smoke Isn’t Always a Serious Problem

A bit of white smoke coming from a lawnmower is a common occurrence with many mowers. If you’ve been a homeowner for a while, you have probably experienced this at least once.

In many cases it is not a serious issue and this problem is easy to resolve, but in some cases may be serious. I’ll tell you about the likely causes, other potential causes, and how to address them below.

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Your Lawn Mower Blows White Smoke Then Dies – Why?

If your lawn mower blows white smoke then dies, this is likely a result of oil getting into the machine’s carburetor. This typically means that the gas feed jet is blocked. In many cases, you will be able to fix this problem by continuing to run your engine until the oil is cleared, but if it’s impossible for you to run the engine for a long enough time, the carburetor probably requires cleaning.

How you clean your mower’s carburetor will depend on the type of mower you have, but if you’re handy at all it’s usually something you can do yourself. I have an article which will help you locate your lawn mower’s carburetor, and that article also provides some tips and resources for cleaning your carb, or replacing it with a new one.

Remember to carefully consult the manual that came with your mower (find it online if you no longer have a hard copy).

You should remove the plug and then try turning over the engine three times. This will help to remove the oil from the cylinder. After you’ve done that, clean and replace the plug. Use some carb cleaner spray like this one on Amazon (you can find these locally as well). Spray it right into the carburetor, replace your air filter, and then try to start the engine again.

If this doesn’t work, you will need to take out the carburetor and clean it.

Other Common Causes of Lawn Mower with White Smoke

Two of the most common causes of white smoke coming from a lawnmower are:

• an overfilled engine, or
• tipping over the mower when getting ready to clean it.

There are other more serious causes, such as a faulty crankcase breather or a head gasket failure, which I’ll go over below.

It’s also possible that your mower’s engine is simply worn out. But in most cases, adding too much gas or tipping your mower and getting gas where it isn’t supposed to be is what causes mowers to emit white smoke.

White Smoke and Burning Oil

White smoke often points to the problem of burning oil. This can manifest in a few different ways in your mower, and burning oil can be caused by the following problems:

• Using the wrong oil grades
• Too much oil in crankcase or exceeding the oil capacity of your engine (you should be able to tell this from the dipstick)
• Crankcase breather inoperative
• Air leak from crankcase
• Head gasket is blown
• Cylinder and/or rings are worn
• You turned or tilted the engine to the side for an oil change or storage (or another reason)
• The breather tube is obstructed (the breather tube is found behind the air filter)

When figuring out engine oil capacity, remember that the capacity depends on the specific kind of engine your mower has.

Check your lawn mower manual for more information, and if you don’t have the original manual, you can typically look it up and download it online by searching your mower’s name and model number plus “manual”.

Why is there White Smoke After Tilting or Flipping My Mower?

Many people will tilt or flip their mower to clean the mowing deck. This is especially true for self propelled and push mowers.

After tipping your mower to clean it, you may notice white smoke coming out of the machine. This happens because oil is able to get into the cylinder. This oil will then burn when you restart the mower, and this leads to the white smoke.

It’s also possible that oil could have spilled and come out of the muffler on your mower, which causes the same type of smoke.

If white smoke comes out of your mower and you recently tilted or flipped it for service, it’s likely a minor issue and the smoke will stop after it burns off. You can check to see whether the oil has made its way where it shouldn’t.

I recommend giving the machine time to idle until there is no more smoke prior to operation. The smoke should clear within about 10 minutes.

Lawnmower Smoke Due to Too Much Oil

If you have a riding mower like a lawn tractor and there is white smoke, this is usually an indication of excessive oil being added to the reservoir, or you may have a fault with the carburetor. It could also be a sign of a blown head gasket, but that is more rare.

Adding too much oil is one of the most common causes of white smoke, so ensure that you only put in what you need when changing the oil in your mower.

Most mower engines need just a little over half a quart to operate smoothly, which is less than you’d think. Accidentally overfilling is easy to do, so be careful when servicing your mower.

While you may believe that too much oil will simply burn off, an excessive amount of oil can actually damage your mower’s engine. Most engines have splash lubrication systems. As a result, if you use too much oil, its level will exceed the splash paddle. You will have problems (such as white smoke) when this happens.

It’s wasteful, and it isn’t great for your machine.

When this is the cause of the white smoke coming from your mower, you are seeing the result of the excess oil being burned. In order to resolve this problem, remove the excess oil and let the engine idle for about five minutes to burn off any excess that remains in parts of your engine it shouldn’t be.

Draining excess oil can be quite difficult for some kinds of mowers, but on walk-behind mowers it’s typically easy (tilt the mower and it drains out of the hole where you added it). If you own a riding mower, investing in a special oil extractor isn’t a bad idea. This one on Amazon runs about $25.

Failed Carburetor Seal

If you have an overfilled oil level and there is a gas smell, your mower may have a failed carburetor seal.

If you think this could be the case, you shouldn’t run the engine. This is because the oil is too thin for it to give your machine the protection it needs. Once you’ve repaired the carburetor, change the oil.

Find information on carburetor cleaning for your type of mower. These should include removing the carburetor, stripping it, cleaning it, and rebuilding it.

YouTube is a great resource for this, because it’s helpful to see the job done before you attempt it yourself.

Failed Head Gasket

While the white smoke coming from your mower probably isn’t caused by a failed head gasket, it’s still a possibility. If your mower has a failed head gasket, there will be an especially large amount of smoke.

The head gasket is made of graphite and metal. It is situated between the cylinder head and cylinder block of the engine. It is there to keep the combustion chamber sealed.

When a head gasket has failed, it can show itself with high crankcase pressures or oil leaks. There could also be a quiet puffing noise. This will be compression escaping from the cylinder. In this case, you will need to replace your head gasket.

White smoke can be caused by a blocked crankcase breather. This situation will also mean there is oil in the cylinder. To deal with this, you should clean out the breather pipe. If you find that you actually have failed or worn piston rings in the end, you will probably need a new engine. A new engine is usually the less expensive option when rebuilding is necessary. A new engine will also come with a guarantee.

Oil Accidentally in the Gas Tank

If there is white smoke coming from your mower, you have possibly put oil into the gas tank. This is quite a common problem. If you’ve done this and need to fix it, drain the gas tank and then put in fresh gas. You can use a siphon or fluid extractor (again, here’s a cheap one on Amazon) to make it easier if you like.

After you’ve cleared the contaminated fuel run the engine until the mower dies from lack of fuel. This should clear out the system so you can replace it with fresh gas.

If the engine still won’t start, you probably need to clean the carburetor.

Best of luck – I hope this article has helped you identify and resolve your mower problem!