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Lawnmower Blowing White Smoke And Leaking Oil Why

Lawnmower Blowing White Smoke And Leaking Oil WhySo your lawnmower is blowing a cloud of white smoke and leaking oil everywhere, each time you turn it on? Are you seeing a heavy smoke show when you start it and when you turn it off there is oil leaking from the air filter? Sometimes it can also leak from the muffler too.

This is the worst situation if you do not know what is wrong with your lawnmower. The answer to this is not simple because there could be several reasons why it happens and we will figure it out together in this article.

Lawnmower Blowing White Smoke And Leaking Oil Why

Lawnmowers are an essential part of the household to keep things right and in place. They help to keep a clean and tidy lawn that looks pleasant and attractive. There are many kinds of lawnmowers available in the market.  Nevertheless, no matter how good of a lawnmower you have at home, this issue can arise with any lawnmower and the reasons behind it are common.

Possible Reasons Why Lawnmower Blowing White Smoke:

1.) There Is Too Much Oil:

The very first whenever you hear that a lawnmower is throwing white smoke out is that there is too much oil inside of it. Too much oil will make it hard to start eventually causing the engine to work harder. The overload of work on the engine can cause overheating as well as smoking. You need to check your oil level to make sure that it has the proper amount accordingly.

2.) The Carburetor:

The carburetor inside your engine brings together air and fuel and mixes them in the proper amount ratio of combustion for the lawnmower to work smoothly. If there is an issue with your carburetor, the mixture may become off.

If there is too little amount of fuel, it can damage your engine and if there is too much fuel it will build up carbon that can lead to a smoking engine. You need to remove the carburetor and give it a good clean. If you notice any damaged components inside, replace them.

3.) The Air Filter:

Dirty air filters are the common cause of a smoking lawnmower. After a while, the dirt or debris can plug up in your lawnmower and it will eventually restrict the amount of air delivered to the engine. If there is not enough air in your lawnmower, it will cause too much amount of oil in the engine. Too little air and too much water can also cause the engine to smoke. The filter should be removed and cleaned or you can replace it after every three months for a smooth experience of your lawnmower.

4.) The Piston Rings:

Pistons rings can be defined as the seal between the piston and the cylinder wall. If either of these components is damaged, the oil can leak through the rings into the combustion chamber and cause engine smoke. To avoid this situation make sure your air and fuel filters are completely clean. In case they are dirty or messing altogether, dirt can find its way into the combustion chamber.

You also need to check your oil, dirty or low oil levels will not lubricate the engine properly, leading to piston and cylinder wear.

Possible Reasons Why The Lawnmower Is Leaking Oil:

The engine of your lawnmower will be at great risk if there is oil leakage. To fix this issue, we need to find out the source of it. You need to immediately stop the lawnmower if you detect any oil leakage and get it fixed.

1.) Lower Oil Seal:

Oil seal is mostly located somewhat near the underside of the engine and it seals the bearing of the crankshaft – the crankshaft helps to spin the blade of the mower – and helps to fix it in the place. If you detect any leakage under the center of the engine. When the lawnmower is on its feet and there is a leakage under the center of it, the most probable reason is that its lower bearing ring seal has broken.

If your lawnmower is blowing white smoke alongside the oil leakage, the reason could be that your lower bearing seal is broken as well as the carburetor is not tilted.

How To Identify?

When you check and there is oil under the engine, wipe it out and wait if it still leaks to confirm that the lower bearing seal is the source of leakage.

Sometimes, the oil only leaks when you run the lawnmower, when it is cool down the leakage might stop.

Also, keep in mind to empty the gas and the carburetor is always in the upwards tilted position to avoid any kind of gas leakage from the lawnmower. This is important because is the old as well as new mowers too, gas can get into the carbon emission vent and ruin it.

2.) Upper Oil Seal:

As it is obvious from its name, the upper oil seal is located on top of the engine and it has a purpose in the lawnmower, to seal the crankshaft when it enters into the crankcase.

How To Identify?

When you run your lawnmower and its engine is on the move, you will notice oil leakage from the top of your engine. The oil will be running down from the sides of your engine and deck.  The only hard part is that seal is covered up with the flywheel and you cannot remove it without proper gadgets, so if you successfully remove the flywheel, you need to check right under it. This is the entering point of the crankshaft into the crankcase.

Now, you will be able to check if the seal is broken and damaged or if there is oil scattered, the oil seal is the cause of the damage here.

You can get the seal replaced to stop oil leakage.

3.) The Fill Seal:

Next on the list is the oil fill seal of your lawnmower. It is located near the crankcase where a tube is attached to it and the oil fill seal can be found at the base of this tube.

How To Identify?

The oil can leak from the dipstick, the chances that the oil is leaking from here are quite low because of the distance between them but as long as there is a possibility, you should consider checking it.

4.) The Fill Tube:

The oil fill tube is a staircase to deliver oil to the crankcase. The oil goes through this tube into the crankcase and that is how it runs on your lawnmower.  A fill tube is connected to the crankcase at one end while at the end of this tube; it has a screwed cap that makes sure there is no leakage.

How To Identify?

You will notice that there is oil gathered either on the tube itself or it can be seen around where the oil fill tube is connected to the crankcase. Another identification can be seen as if there is oil leakage on the deck of your lawnmower.

Just like other identification methods, remove oil from all parts, turn on the mower again and see what is the source of oil leakage here. If the oil is coming from the tube itself, it is most probably damaged but, if it comes from the joining point, there is a high possibility that the oil seal is broken.

Either the tube itself or its seal, you will need to replace them for your lawnmower to function again.

5.) The Crankcase Gasket:

The last reason why your lawnmower is blowing white smoke and leaking oil is the crankcase gasket. It seals around two-thirds of the crankcase and it does not seal the crankcase cover. It covers the crankcase normally from the back to the front.

Now, what type of gasket you have installed on your lawnmower depends because some of them are liquid, paper, or even rubber built. All of them are good it does not even matter which one of them you are using because if it is broken, it will not do the work.

Check out the More Lawn Mower Tools from our Website.

How To Identify?

The very first thing you need to do is find out the crankcase cover and then where the gasket is attached. Once the seal of the gasket is found, you need to check if there are any traces of oil here. In case, you find the oil in your crankcase gasket. The very first assumption is that your gasket is damaged.

Again, clean up all the oil, use your lawnmower again and check if there is oil building up again in the specific area.


There could be several reasons for the question, of why lawnmowers blow white smoke and leak oil suddenly. After doing thorough research we have jotted down a few possible reasons for the situation. The possibility to remove all these errors at home is quite low because not many people are good with the mechanics of it, but it is highly recommended as soon as you smoke and oil comes out of your lawnmower, else, there is a huge danger to its engine.

Tom Hanks

Tom Hanks is a DIY lover and an expert of tools to give you detailed unbiased reviews and guides on using and buying great tools for your DIY projects.

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