White Smoke from Exhaust – Main Causes & Fixes

Smoke from car exhaust can be of various types and can be because of a variety of reasons and situations.

Ranging from blue, grey, white and blue, every type directly or indirectly is because of a distinct phenomenon.

Generally, it is suggested to take your car to mechanic or technician if you experience any smoke from the car’s exhaust, but white smoke that we are discussing here may not necessarily be because of any malfunctioning.

First of all, it is necessary to assess whether the white smoke is of very low density, in which case it is thin or somewhat like vapor and it disappears shortly, or is it of thick density, flowing continuously with a burning type aroma.

It is highly suggested to consult a mechanic but to make sure he does not fool you with technical terms, maneuvering you from the main problem and letting you spend loads on other unnecessary aspects of your car. It is always better to get some knowledge for a better understanding of what you are up to.

Causes of White Smoke from the Exhaust Pipe

White smoke, as mentioned above, can either be very light just like vapor or it can be dense and heavy smoke.

White smoke from the exhaust pipe on startup, idle or acceleration is telling us that there is coolant or water that is getting vaporized. You can taste the water from the exhaust; if it smells swee,t it’s most likely coolant, and in this case, you have a bigger problem.

If the smoke emitted is of high density or thick, then you have to get a proper diagnose for your vehicle, because condensed coolants are never good for your engine. Let’s start with the most common causes of white smoke.

1. Condensation

The most common reason for white smoke from the exhaust pipe is that it is condensed in the exhaust pipe. White smoke that is like vapor and disappears soon could is likely caused by condensation. Steam is emitted by condensation in the exhaust pipe which is seen at the exhaust emission. But it is fine and is nothing to worry about as long as your car is maintained.

If the white smoke is light and just coming from the startup moment at cold starts, there should be nothing to worry about, because it’s most likely just condensation.

2. Bad EGR Cooler

If your exhaust smoke smells sweet, it’s most likely condensed coolant you are faced with. The most common cause of this on modern vehicles is because of a crack inside the EGR cooler. This can be pretty difficult to diagnose properly as there are no signs you can look for on the outside of the engine.

However, if the EGR cooler is cracked, it has to be replaced. If you suspect that your EGR cooler is faulty, you may have to get help from a mechanic to diagnose it properly. The best way is to use a coolant leak tester and to take the EGR pipes off to see if you can see any coolant is entering the exhaust pipe.

3. Bad Head Gasket/Cracked Cylinder Head

When the car’s cylinders head or gasket is either damaged or cracked, even a small crack, coolant starts to leak out of it and gets mixed with engine oil. This mixing results in contamination of engine oil, and ultimately results in white exhaust smoke with a sweet odor.

If you want to go further into bad head gasket diagnosing, check out our other article here: Bad Head Gasket Symptoms.

The engine will have to get taken apart and be repaired but if not repairable then in the worst case, it will have to be replaced, resulting in high costs.

4. Faulty Coolant Container/Tank

Leaking of the coolant tank can also be one of the reasons for white smoke. Although it is very rare that the coolant’s tank breaks, it can get damaged. Damage could be have been done while repairing some other nearby part, all of the sudden damaging reservoir tank. However, if this happens, the smoke will come from the engine and not from the exhaust pipe.

Whatever the reason is, it needs to get replaced as there is no other possible option. Replacing it is not a big deal and will not affect the car’s performance after replacement.

5. Oil Leakage

Another possibility is when oil starts to leak from the piston or if valve seals go faulty. This results in oil leaking into the combustion chamber and getting mixed with fuel that is to be burnt. Burning of this oil and fuel mixture results in blue smoke from exhaust hinting that your engine is prone to more wear and tear as oil is leaking and no proper lubrication is available for the engine’s components to work smoothly.

It is worth mentioning that when oil is combusted, the oil is blue rather than white.

To fix this problem, usually the seal will have to be replaced, ultimately by detaching the engine’s main part and then putting its new seals, which will result in high cost as well due to excess labor activity.

6. Faulty Fuel Injectors

The purpose of fuel injectors is to provide an engine with a sufficient amount of fuel and to make sure that neither more nor less fuel is provided to the engine. In case of these injectors getting faulty, the improper supply of fuel leads to over burning of fuel, resulting in gray, dense smoke from exhaust.

An overly rich mixture will produce black or gray smoke, but it can easily be mixed with the white smoke. Let a mechanic take a look at the smoke to tell you if it’s coolant, fuel or oil that is getting burned.

If the Fuel Injectors are faulty, they have to be replaced, the price of which depends on your model and make.

How to Diagnose a Car With White Smoke from the Exhaust

There are several ways to diagnose a car with white smoke. However, some mehtods are easier and faster than others. I work as a mechanic, and this is the way I would diagnose this issue.

Smell the Smoke

The first thing you should do is to taste the smoke coming from the exhaust pipe. If it has a sweet smell, it’s coolant, and you can continue with this guide. If the smoke doesn’t smell or taste of anything more than water, it’s most likely condensation and the smoke will go away after the car is heated up.

Use a Pressure Tester

The best and only (in my opinion), way to find internal coolant leaks is with a coolant pressure tester. You fit it on your radiator cap and put pressure inside the coolant system and let it stand for an hour. Remove the spark plugs or glow plugs and check for any signs of coolant leaks entering the combustion chamber. If you notice coolant there, you might have a problem with your head gasket or a cracked cylinder head.

If you can’t find any coolant there, remove the pipes to the EGR pipes and check for any signs of coolant inside of them. If you notice coolant, there is most likely a crack in the EGR cooler, and you have to replace it.

If you consider purchasing one, I can recommend this kit from Amazon: 8MILELAKE Universal Radiator Pressure Tester Kit

Conclusion

So basically, smoke can be of various types, but white smoke that we have above discussed in detail could be a result of both, fault and general combustion. But in the case of a fault, it can get repaired depending on the nature of fault that will decide how much will it cost to repair it and most important of all, if it is worth repairing.

If you have any other questions regarding white smoke from the engine or exhaust, comment below!

Magnus Sellén

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.