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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