Lawn Mower Smoking: Reasons Why & How To Fix Them. Lawn mower black smoke

Why Your Lawn Mower Blows Blue Smoke.

It’s a beautiful day and you head outside to mow the lawn. Probably thinking that you could be doing better things. This feeling is compounded when you start to see smoke rising from your mower. Although this is annoying it pays to do a few simple checks before running off to the local fix-it shop.

There are a few things that can make your mower smoke and although it may appear to be something major it is normally a simple fix.

A lawnmower blows blue, white or black smoke for the following reasons.

  • oil reservoir has been overfilled.
  • The mower has been tipped on its side.
  • Choke needs adjustment.
  • The air filter is blocked.
  • The carburettor needs adjusting.
  • The spark plug gap is wrong.
  • The engine is worn.

The colour of the smoke is a clue about the problem and in my 30 years of commercial lawn mowing I have encountered all of them.

This is a simple list I would give to my employees to go through before they contacted me. If you run through this simple checklist you should be able to self-diagnose the problem, fix it, and get back to that lawn.

The mower blows out Blue or White smoke.

This is a sign that the engine is burning excess oil. The excess oil in the engine causes incomplete combustion which will create smoke and a carbon buildup. The engine may run like this for a while but eventually, it will foul up and become increasingly hard to use and eventually die.

Has the oil reservoir been overfilled?

The first thing you should do is check your dipstick. If you cannot find a dipstick then you have a two-stroke engine go to the bottom of this post and I talk about two strokes there.

If the oil is above the maximum full lever on your dipstick then is a problem. You will need to drain some oil out of the mower. There are a few ways to do this.

  • Unbolt the sump plug. This is usually the engine manufactures recommendation. A word of warning here. Not all engines have a sump plug so if you cannot find it go to step two. Remember to access under the mower by lifting the front wheels up, not by flipping the mower on its side. (you don’t want to compound the problem). In most cases, you will need to remove the blades.
  • Remove the dipstick and tip the mower on that side. I know that in step one I said don’t tip the mower, but it is ok if the dipstick is removed. As long as you do not tip the mower on the filter side you will be fine. It is a good idea to run the mower for a few minutes first (this makes the oil flow better). Drain out a bit of oil and check the level again. Do this until it is on the right level on the dipstick and then run the mower for about five minutes until the smoke clears.
  • Use an oil extractor pump. This is the tool that most mower shops will use. I would suggest method two but if you are going to be doing this a lot then an oil extractor may come in handy in the future. This is a good one made by Briggs Stratton on Amazon. Again run the engine for a few minutes before draining the oil.

If you are not sure how to use an extractor pump then the Briggs and Stratton website has a video that walks you through this procedure.

Do remember that if your mower was smoking you have probably fouled up the spark plug as well. You will need to clean or replace it.

Finding the sump plug.

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Has the mower been tipped on its side?

If your mower has been tipped on its side then this could be the problem.

This can happen if you flip the mower without thinking if something tangles up on the blade or cleans under the mower. It is even possible for this to happen when you are mowing on a slope if the angle is great enough. This is more likely when you are mowing across a steep lawn rather than up and down.

If you flipped the mower with the muffler side towards the ground then you may have got oil in the muffler. Provided it wasn’t left like that for too long this should burn off. Let to mower idle for five minutes and see if it clears up.

If you tipped it on the air filter side then that is not as easy. First, check your air filter. If it is full of oil you are going to have to clean out the holder and replace the air filter. If you do not have access to an air filter immediately don’t worry too much, the mower will run ok without it while you finish the job. Just make sure to replace it before you use the mower again.

Now top up your oil, clean or replace the plug and you should be good to go.

Is the choke working correctly?

Check the cable attached to the on/off switch. Make sure it is not sticking in the choke position. This can cause too much fuel to get through which will create smoke and a badly running engine. Spray the top and bottom cable with Lubricating Oil and work the on-off lever.

Check to see if this has solved the problem.

If this does not solve the issue or you have an automatic choke then you will need to get this checked at your local mower shop.

Ware and tear on the engine.

If you can find none of the causes above it may be the engine and you will need a compression test.

This could be any excessive wear on the engine but it is usually a worn cylinder, rings, or the sign of a blown head gasket. All of these things will need to be done by an experienced mechanic so do not attempt to fix this unless you know what you are doing.

The mower blows out black smoke.

This is caused by the engine burning more fuel than air. Too much air leads to partial combustion and the excess fuel can turn into smoke.

The air filter may be blocked.

Pull off the air filter. Clean it by tapping it on the ground or by using an air compressor. Clean out the housing and replace the filter if it is too far gone. To test simply pull the filter out and start the mower. If the mower starts and doesn’t smoke then it is the filter.

If you have a foam air filter then you could wash it in warm water with a few drops of dishwashing liquid. Wring the water out and leave it to dry naturally. When dry I put it in a plastic bag with a little bit of Foam air filter oil then I squeeze the bag to evenly distribute the oil. This last step is not necessary but I prefer doing it as it catches dust better, especially if you work in dusty environments.

lawn, mower, smoking, reasons

Your air mix on your carburettor needs adjusting.

This is normally a screw that you can adjust on your carburettor called the idle adjustment. You can turn the screw and it will adjust the idle on your engine. You can slow the engine down if it is idling too fast or vice visa.

How to Adjust your carburettor video

I normally just throw a new plug into the mower if I have any problems. This is the first thing a mower shop does when you bring a lawnmower in. They are only a few dollars each so its always worth having one on hand.

A Faulty crankcase breather.

If you have ruled out everything else excessive oil consumption and smoke can be the sign of a blocked crankcase breather.

Unless you are handy with engines then you would probably want your local mower shop to do this.

Two-stroke engines blowing smoke.

The first thing you would want to check with a two-stroke engine is that you have used the correct two-stroke oil at the right mix. If the oil mix is too heavy then it will cause the engine to smoke.

You do not want to just add petrol to dilute the mix because if you dilute the mix too much you will risk seizing the engine which is even worse.

You can check that you have the correct oil easily enough but there is no easy way to check the mix in your tank. I always say “if in doubt then throw it out” better safe than sorry.

There is normally a small fuel hose that attaches underneath the tank held on by a butterfly clip. Unclip that and drain your tank. Reattach it and put it in the correct oil/gas mix. If the engine stops smoking then you have found the problem.

If there is still smoking go through the list above starting at “Is the choke working correctly?”

Nobody likes a smokie mower and hopefully, by now you no longer have one.

Now that your mowers are fixed, you can get back to that lawn. Time to mow the lawn while daydreaming about all the fun things you could have done today instead of fixing a mower.

Lawn Mower Smoking: Reasons Why How To Fix Them

It can be an alarming sight when you fire up your mower and instead of running smoothly, it starts billowing smoke – especially if it starts sputtering and stalling too. While it’s understandable that your immediate reaction may be to panic, very often the source of a smoking lawn mower or engine is an innocuous issue that will go away on its own or with a simple DIY fix.

When assessing the severity of a smoking lawn mower, the clue is in the color of the smoke. In the majority of cases, a lawn mower smoking white or blue smoke will stop producing the smoke on its own after you let it run for a few minutes. However, if the smoke continues to billow out of your mower and you notice other telltale signs that the mower’s engine isn’t running the way that it should, you may need to address the issue yourself or have it repaired by professionals. A lawn mower smoking black smoke is also a cause for concern and indicates there’s an issue with the inner workings of your mower.

Read on to learn more about the different causes of a lawn mower smoking white, blue, or black smoke, along with step-by-step guides on how to fix each issue at the source.

Before following these troubleshooting tips, make sure you’re using the right technique to start your lawn mower by referring to our guide: How to Start a Lawn Mower.

Why is My Lawn Mower Smoking White Smoke?

Oil Spilled on the Engine

Mower oil spilled onto the engine can be a cause of the lawn mower smoking white smoke. If you notice your mower smoking after adding oil, you may have accidentally spilled some of the oil onto the engine’s housing. Oil may also inadvertently spill onto the engine if you’ve been mowing on a slope steeper than 15 degrees, or if you’ve tipped the mower onto its side for any reason.

How to Fix an Oil Spill on the Mower’s Engine

The smoke may appear alarming, but this issue is relatively minor and is easily fixed using the steps below.

Restart mower’s engine

Simply restart the mower’s engine and allow the spilled oil to burn off.

Wait until white smoke stops

If the white smoke doesn’t completely dissipate after about 15 minutes of running the mower, it’s an indication that there may be a bigger issue that needs to be addressed. If this is the case, see the following sections where we have gone through the next steps you should take towards identifying and solving other potential causes.

Oil in the Fuel of a 4 Stroke Mower

If you don’t own a 4 stroke mower then you can skip this section. In the case that you do have a 4 stroke mower, it may be smoking white smoke due to oil mixing in with its fuel. Many up-to-date lawn mower models come with a 4 stroke engine, as they are more reliable and tend to have a longer lifespan than 2 stroke engines do. Not only are they more reliable, 4 stroke engines require less maintenance than their 2 stroke counterparts, and don’t require oil to be mixed in with its fuel. If you put fuel that has been mixed with oil into a 4 stroke mower engine, then the mower will burn the oil which causes it to smoke white smoke. If you continue to run the engine of a 4 stroke mower when there’s engine oil in the fuel tank, it may lead to the engine becoming damaged and prematurely worn out.

How to Remove Oily Fuel from a 4 Stroke Mower

You should take care to avoid draining the fuel out of the mower by tipping it, as this can cause engine oil to spill into the carburetor or cylinder.

Find fuel line

Locate the fuel line, which is the part that exits the fuel tank responsible for feeding fuel into the mower’s engine.

Remove fuel line

Undo the clip on the fuel tank that’s holding the fuel line in place and pull the fuel line off. Alternatively, you could follow the fuel line to where the shut-off valve is located and remove the line at the point at which it connects with the valve. The shut-off valve is a small switch that enables the user to control the flow of fuel to the engine, and is easy to spot around the base of the fuel tank. Be aware that when you complete this step, fuel will start pouring out of the tank.

Drain fuel from fuel tank and collect it in appropriate container

After you remove the fuel line, fuel will start pouring from the fuel tank. Use an appropriate container such as a metal pan to collect it and prevent it from spilling everywhere. Spilt gasoline is not only a nuisance, but also a serious fire hazard, so make sure to clean up any liquid that you don’t manage to contain.

Drain fuel from carburetor

As you drain the fuel from the fuel tank, find the carburetor on your mower to drain the fuel from it as well. Underneath the carburetor you will find the carburetor bowl, which has a small screw or nut located on the side or bottom of the bowl that can be tweaked to empty it out. Loosen the screw or nut and allow the fuel to drain out of the carburetor into your container.

Wash fuel tank if necessary

This step is unnecessary if you can’t see any oil stuck to the inside of the mower’s fuel tank. If you do, then you will need to remove the tank from the mower completely and give it a deeper clean with dishwashing liquid. Pour dishwashing liquid into the fuel tank and give it a good shake to remove the oil from the inside of the tank. You can then clean the carburetor using a can of carburetor cleaner.

Overfilled Oil Reservoir

If your lawn mower is leaking oil and smoking white smoke, you may have accidentally overfilled the crankcase. Lawn mowers suffer from having too much oil as much as they do from having too little. An excess of oil in the reservoir can spill into the engine’s cylinder and start burning with the fuel, which can cause white smoke to come from the mower’s exhaust and oil to start leaking from the muffler. Excess oil in the mower can also leak onto the housing of the engine, which causes the mower to smoke white smoke when the engine heats up and burns it off. In addition to creating the white smoke, the excess oil may also drown the mower’s crankset, impeding its motion. If the mower’s engine won’t start, or takes a much longer time than normal to start and you find that it’s difficult to idle it, these are telltale signs that the combustion chamber is burning oil.

How to Fix Prevent an Overfilled Oil Reservoir

It varies between models, but generally speaking, lawn mowers take just over a pound of oil. This isn’t very much, which is why it’s common to accidentally overfill the oil reservoir. Check the manual for your mower to find out the exact recommended amount of oil for your model.

Check current level of oil

Use the dipstick to check whether the oil level is within the indicated amount marked on the stick. If it shows that there’s an excess amount of oil in the engine, follow the next steps to fix it. You may need to seek the help of professionals if the oil is present in unmanageable amounts.

Drain excess oil

Remove the excess oil by draining it out of the engine. Tilt the lawn mower onto its side so that the carburetor is facing upwards in order to prevent oil from spilling into the combustion chamber. Let the oil run out of the mower into an appropriate container, and clean up any oil that spills onto other parts of the mower. Dispose of the excess oil appropriately. Finally, change the oil filter.

Check new level of oil is adequate

Use the dipstick to ensure that the new level of oil is within the recommended amount. Run the mower and wait until the white smoke dies down. If it doesn’t, refer to the next section.

Damaged or Leaking Head Gasket

If neither of the previous two issues are the source of the white smoke coming from your mower, then it could be due to a damaged or leaking head gasket. The head gasket is a seal that functions to keep the engine closed off, and is found in the area of the mower where the cylinder joins with the rest of the engine. When this part of your mower fails to seal the cylinder head properly, it can cause oil to leak from the crankcase into the cylinder. As there is a lot of compression in the cylinder to pull oil from the crankcase, any small crack in the gasket will cause oil to be sucked into the combustion chamber. The oil will start burning as it enters the cylinder, and will cause the mower’s engine to produce clouds of white smoke. If the engine is left running, it will only cause the mower to produce increasing amounts of smoke as more oil is sucked through the damaged gasket into the combustion chamber. In addition to your lawn mower smoking white smoke from its exhaust, you will be able to hear the air that’s blowing from the faulty gasket, and you will notice a reduction in compression which can cause the mower to have a low power output. If there is a large amount of oil flowing into the cylinder, it may cause the mower to die after a few minutes of use or prevent it from starting at all.

How to Replace a Damaged or Leaking Gasket

Only Overhead Valve (OHV) engines have gaskets, so make sure your mower definitely has an OHV engine before taking it apart. Examine the head gasket for signs of damage, such as oil around or under the gasket and on the body of the mower. If the head gasket does appear to be damaged, it will need to be replaced as these parts aren’t repairable once they’re damaged. They are inexpensive so you’ll be able to purchase a good quality replacement for a relatively small amount of money. You can DIY and replace the head gasket following the steps below.

Remove spark plug wire and cylinder head bolts

First, remove the spark plug wire, then use a socket to remove the bolts holding the cylinder head onto the engine block.

Remove damaged gasket

The gasket is found where the cylinder head connects with the engine block. Remove the old damaged gasket. Use a tool to scrape off any remaining spots of hard-to-remove parts of the gasket, but take care not to scratch the smooth surface when scraping off the leftover debris.

Install new gasket

Take the new gasket and place it on the engine block, then replace the cylinder head before bolting the gasket onto it. Reinstate the spark plug wire onto the spark plug.

Damaged Piston Rings

The worst culprit of all that may be causing your lawn mower to smoke white smoke is a damaged or worn out piston ring. Piston rings are responsible for controlling the flow of engine oil within the mower, supplying small amounts of oil to the piston to enable it to move smoothly within the cylinder. The piston rings in your mower also work to expel excess oil out of the combustion chamber and to channel it back into the engine block. When the piston rings fail to work properly, engine oil is able to enter the combustion chamber where it gets burnt up, which is what then causes the mower to smoke white smoke. This is an issue commonly seen in older and worn out lawn mowers, or in mowers that have been poorly maintained. Piston rings can become damaged through a number of different ways, but one of the most common causes is if the mower has a dirty or worn out air filter that has allowed dust and debris to enter the combustion chamber where it has managed to damage the piston rings. Another extremely common cause of piston ring damage is if the engine oil hasn’t been changed on time or has become dirty, as this results in poor lubrication and wears out the piston rings. In addition to the white smoke, your mower will run with little to no power, and will burn through a lot more oil than it should need.

How to Fix a Damaged Piston Ring

Unfortunately, fixing a damaged piston ring is a complicated job that requires the engine to be opened up and rebuilt entirely. If the piston rings in your mower are damaged, it’s likely that the head cylinder will also be damaged to some extent and will need to be replaced too. You would need specialized tools and a lot of experience to carry out this type of repair, so unless you are a lawn mower expert, it’s probably best to seek the help of a professional repair shop instead of trying to DIY it. Alternatively, you can just replace the whole engine, which is probably the best option at this point as rebuilt engines tend not to work as well as new ones.

Why is My Lawn Mower Smoking Blue Smoke?

For the most part, a lawn mower smoking blue smoke is likely to be suffering from one of the issues known to cause white smoke – read through the previous sections to find out more about the potential causes of blue or white smoke. Other possible reasons why your lawn mower is smoking blue smoke can be due to the use of the wrong oil grade, or if you have over-tilted the lawn mower when mowing on a slope.

Why is My Lawn Mower Smoking Black Smoke?

Dirty or Worn Out Air Filter

Dirty or worn out air filters are a common cause of lawn mowers smoking black smoke. The air filter in your mower ensures that the air flowing to mix with the gas is clean and free of contaminants such as dirt, dust, and leaves, which would potentially damage the mower’s engine. When the air filter becomes dirty or worn out over time, airflow is restricted and the combustion mix becomes too gas-rich due to the reduced amounts of oxygen. This can cause black smoke to pour out of the mower’s muffler, and may also cause the mower engine to stall after a few minutes of use.

How to Clean an Air Filter

We’ve provided some rough guidance below on how to clean an air filter, but you can refer to your mower’s manual to know the exact instructions for your model. If the filter is severely clogged, it may be easier to just replace the part entirely.

Clean light dirt with compressed air

As air filters are made from a sturdy and porous material, you can use a can of compressed air like the Innovera Compressed Air Cleaner to clean out light amounts of dirt.

Clean heavy dirt with lukewarm water water and dish soap

If the air filter is severely clogged and needs more of a deep clean, you can remove it completely from the mower and hand wash it. Fill a bowl with lukewarm water and dish soap, and remove as much of the debris as possible. Let the filter air dry and then replace it in the lawn mower.

Run the engine and check for smoke

Run your mower’s engine for a few minutes and check if it’s still smoking any black smoke. If it is, then the issue may lie with the carburetor instead. See the next section for more information on this.

Malfunctioning Carburetor

If your air filter isn’t the problem, then the next source of the issue could be with your mower’s carburetor. The carburetor and other parts of the fuel system work together to mix oxygen and gas in the right ratio to create combustion, which in turn regulates the flow of fuel to the crankshaft that powers the lawn mower’s engine. When airflow to the carburetor is restricted, the fuel mixture becomes too rich in gas, and this can cause the mower to smoke black smoke from its muffler. Other signs of a malfunctioning carburetor in a lawn mower include the mower’s engine stalling during use or failing to start at all, the engine running roughly during use, and the mower consuming more fuel than usual.

How to Clean a Carburetor

Find the carburetor located on the side of the mower, behind the air filter and on the opposite side to the muffler, and inspect it. If the carburetor appears damaged or worn-out, you may need to replace the part entirely. If it’s just a case of a blocked or dirty carburetor, you can follow the steps below to remove the blockage and get it functioning properly again. If neither of these things seem to be the issue, it may be necessary to adjust the carburetor to increase airflow.

Remove carburetor bowl and its screws from mower

Use a plug wrench to loosen the screws holding the carburetor bowl in place, and remove them along with the bowl from the mower.

Clean carburetor bowl, hole and screws

Purchase an aerosol carburetor cleaner and use it to clean away any debris or residue from the carburetor bowl and screws. Aerosol carburetor cleaners are cans of pressurized air specially designed to clean carburetors, and some brands come with directional nozzles that help get into the harder-to-reach corners of the part – this Carb and Choke Cleaner from Gumout will do the trick. To remove any blockages, use a thin piece of wire or a nylon cleaning brush to clean out the hole that sits underneath the carburetor – we like to use the wire needles in this Cleaning Tool Kit to break through any tough debris.

Replace the carburetor bowl and screws

Take your plug wrench again and use it to reattach the carburetor bowl and its screws. Take care not to over-tighten the screws when replacing the bowl as this may distort the seal.

Our East Coast editor Frank focuses on lawn cutting and maintenance. His experience with lawn mower repair and lawn maintenance is second to none.

He is a lawn mower and fertilizer expert with over 30 years of experience in the industry. He has been providing advice to homeowners and businesses on lawn care since 1990 with his lawn maintenance business based in the small town of Waterbury, Connecticut.

White Smoke From Lawn Mower: What It Means And How To Fix It

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If there’s white smoke coming from your lawn mower, don’t freak out!

There are two common causes – spilled oil or too much oil – and both have simple solutions. You’ll either need to burn off the oil on your engine, or drain some oil from your reservoir.

Is your lawn mower smoking? Here’s what that means and what you can do to fix it.

Why is My Lawn Mower Smoking?

There are a lot of different reasons for your mower to spew smoke. Common causes include excess oil, a blown head gasket, not enough air in the gas tank, or a dirty air filter.

What Does White Lawn Mower Smoke Mean?

lawn, mower, smoking, reasons

For lawn mowers spewing white smoke (or even blue smoke), the likely culprits are an overfilled oil reservoir or oil spilled onto the engine.

You may have overfilled your mower with oil, which then spilled over and caused engine smoking.

Alternatively, if you’ve been mowing on a slope greater than 15º or if you’ve tipped your lawn mower sideways to inspect the mower deck, the oil will spill.

If you’ve accidentally turned your lawn into a DIY rave, there’s no need to panic. White smoke is generally harmless and easy to fix.

Quick Fixes for a Smoking Lawn Mower

Step one, if there’s smoke from a lawn mower, is to shut off the engine immediately. Your safety is the main priority here, so turn off your mower until the smoke clears.

For electric mowers, take out the spark plug so you don’t risk a fire hazard.

After the mower cools and the haze is gone, check the air filter.

For a dirty or clogged air filter, you’ll need to clean it. For a worn-out air filter, you’ll likely need to change it out.

If that’s not the case, replace the parts and restart the mower. Let it run for about 5–10 minutes to burn off any oil that could have entered the lawn mower engine.

If there’s no more blue or white smoke, you should be fine.

How to Fix White Smoke from Lawn Mower

If the quick fixes don’t work and you’ve run your engine for about 10 minutes, then it’s time to get down and dirty. Identify the cause of your white smoke and use the appropriate solution.

White smoke from spilled oil

lawn, mower, smoking, reasons

Oil spills in mowers have a few common causes:

  • Worn-out seals in the combustion chamber
  • Cracked crankcase or air leak
  • Mowing a slope of over 15º incline
  • Tipping the mower on its side
  • Overfull oil reservoir
  • New mower with leftover oil residue

The excess lubricant will leak out onto the mower’s engine, where the oil burns and causes smoke.

In this case, just restart the engine and let it run. Eventually, all the oil will burn off and the engine will stop producing white smoke.

To stop this issue from reoccurring, target the source. Check the owner’s manual for ways to limit oil leaks.

If your lawn has a steep slope, consider levelling it so it places less stress on your mower.

White smoke from too much oil

Double-check the oil level to ensure you didn’t overfill the reservoir.

Use the dipstick to check the engine oil (remember to wipe the dipstick clean first so you get a good reading). Compare the level to the “fill” line on the stick.

If the level is too high, you’ll need to drain oil from the reservoir. Follow the instructions in the owner’s manual for draining and refilling the oil to the fill line.

You may also be using the wrong grade of engine oil, which could cause lawn mower smoke.

Other Smoke Problems

The smoke from a lawn mower might not just be white – sometimes you’ll get blue or black smoke as well. If that’s the case, here are some potential causes.

Black smoke

If you’re getting black smoke from your mower, the issue may be a too-rich fuel mixture.

The carburettor regulates the proportion of gasoline and air mixture, but if it’s not getting enough air, it causes black exhaust smoke.

The usual cause for this is a clogged air filter that’s limiting air flow. You may also need to adjust the carburretor.

Blue smoke

The causes for blue smoke are generally the same as white smoke – spilled oil or too much oil. The smoke is simply a different colour, usually the result of higher combustion temperatures.

Maintain Both Your Mower and Your Lawn

If the smoke problems persist, or you discover a deeper engine problem that you can’t fix, it’s better to take your mower to a repair shop.

You may also need expert help to change the seals on the combustion chamber or fix an air leak in the crankshaft.

For those who hire professional mowing services. keep yourself available in case they report smoke issues with your mower! You can also check to make sure they know these solutions in case a problem arises.

Check your lawn mower regularly to ensure everything is in working order, from the engine lubrication system to the oil seals.

Frequent check-ups let you catch malfunctions or damaged mechanisms before they can cause bigger problems.

Knowing how to tackle white smoke from lawn mower will save you some stress in the long run. Not only will it help your mower last longer, but your lungs will be more thankful – and you’ll get fewer complaints from neighbours too!

Jamie Donovan

Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.

Why Does My John Deere Smoke? [Causes Solutions]

You’re bound to get some anxiety when you notice smoke spewing from the exhaust or elsewhere on your expensive John Deere Mower. How bad is it? How much is it going to cost to get it fixed? Is the damage permanent? These are all reasonable questions, but there’s no reason to panic.

There are several potential causes behind smoke pouring out of your John Deere. Low coolant levels, low engine oil levels, too much oil, bad injectors, plugged air filters, and leaking head gaskets are some of the most common reasons for a smoking John Deere.

Fortunately, all of the above is repairable, and although a leaky head gasket sounds complicated, it’s not as bad as you think, and it’s also one of the rare causes on the list.

There are also cases where there may be white smoke, and nothing is wrong with your mower.

Potential Causes and Solutions

Nobody wants to see smoke spewing out of their lawnmower, especially if it’s a new John Deere, but it happens. So, the next step is ascertaining the problem. Where it’s coming from and how to fix it, hopefully on your own.

DIY repairs are the best way to go if you have the tools and capacity, especially when it comes to a John Deere because they don’t just hand out repairs for free.

However, if you have it under warranty, that’s a different story. Warranty or not, what could be the source of the smoke?

Low Coolant Level

Low coolant levels are easy to ascertain as you can simply check your coolant level and ensure that it is where it’s supposed to be. Of course, you want to let your mower cool down before you pop the cap.

When the coolant gets too low, overheating occurs throughout the engine, and while it won’t smoke like crazy, you will see some white smoke coming from the engine. If you own a relatively new John Deere, there’s a chance that you have low coolant because there is a slow leak somewhere.

You should top your coolant off, but you should check all of the connections in and around your radiator and observe it carefully while it is running.

Air Filter

There are three things required for combustion: air, fuel, and spark. If your engine isn’t getting enough air, then it is probably running “rich,” a term for too much fuel and not enough air for proper combustion. This will cause black smoke rather than white, and one of the first suspects is the air filter.

You should remove it and clean it thoroughly (use compresses air to blow it down if you can), but you should also include your air filter in your routine maintenance procedures.

Oil Level is Too High or Too Low

Lack of lubrication will certainly produce smoke, as you will have an increase in friction and heat from moving parts within the engine that are not properly lubricated.

The problem with low oil levels is that by the time you notice it (thanks to all of the smoke), there will likely be side effects throughout the engine.

Also, like the coolant levels, if your John Deere is relatively new or well taken care of, a low oil level is likely a sign of a leak somewhere.

Too much engine oil is nearly as problematic as the reverse. Excess oil burns off and increases pressure in the crankcase. The burning off creates smoke and, as a side effect, will damage or clog your air filter as well.

You’ll need to drain the oil and change or clean the air filter. Whenever you put oil in the mower, always use only the recommended oil type and the exact amount specified in the user manual.

Bad Injectors

If your injectors aren’t working correctly, you will not get the right amount of fuel. This usually leads to fuel that isn’t burned away and leftover fuel that isn’t ignited. The typical result is white smoke. However, the John Deere will also show signs of sluggishness, vibration, or otherwise just not running right.

Depending on what John Deere you have, the process for changing the fuel injectors can be drastically different. Fortunately, there are a lot of YouTube videos on the process. Also, if your John Deere is under warranty, you will want to take it in rather than risk voiding the warranty trying to repair it yourself.

There are also several fuel injector cleaners you can try first, as that might be enough to resolve the problem without having to get it repaired.

Leaky Head Gasket

If your John Deere is pretty new, a leaky head gasket is undoubtedly something that will be covered under warranty, so long as you haven’t done anything that would directly cause damage to a head gasket.

This is probably one of the more difficult things when it comes to a DIY fix, so if you are not a John Deere Tractor or Mower mechanic, it might save you a lot of headaches to just take it in for a repair.

It may be on the expensive side, but it’s not as bad as purchasing a new John Deere.

White Smoke, Black Smoke, and Blue Smoke

White, black, or blue smoke might not tell you exactly what the problem is, but they will point you in the right direction if you know what they mean.

Black Smoke

Black smoke is usually caused by burning too much fuel without enough air. Most of the time, that indicates bad injectors or, more commonly, a clogged-up air filter. If your air filter is relatively clean, there is an air restriction somewhere, which might be a problem with the choke.

Blue Smoke

Blue smoke is usually the direct result of burning oil. It’sIt’s just the color that tends to come from it when it is burning rather than lubricating the moving parts throughout your engine. Sometimes, the blue can be really dark, and that might mean that you have multiple issues going on.

If you see blue smoke, check your oil levels to ensure that the reservoir wasn’t overfilled during your last oil change or that there is plenty of oil there.

It’s mostly going to be a problem from excess oil. However, leaking oil can find its way into places hot enough to burn it off, and you’ll notice a low oil level.

White Smoke

You get white smoke from leaky head gaskets and gas in the oil or vice versa. Diesel engines are more prone to white smoke, but that doesn’t mean you will never see it in gasoline engines.

Diesel fuel filters that aren’t working properly can cause white smoke, and out of three colors of smoke, this one will be the most prevalent, especially in diesel engines.


Signs of smoke emanating from your John Deere aren’t the end of the world. However, there is always cause for concern.

The best thing to do is address the smoke immediately and locate the cause, even if you discover that the cause is nothing damaging.

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  • Why Does My John Deere Gator Grind When I Put It In Gear?
  • Can I Use Synthetic Oil In My John Deere Riding Lawn Mower?


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I love working in the yard and coming up with projects around the house. In addition, I am blogger. I’ve decided to start this blog to share stuff I learn about yard work, or any projects that are house related. These days I blog about everything related to anything pertaining to the outside of the home. Everything in this blog should be used for educational purposes only. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Privacy Policy

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