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Car Smokes when driving

Why Does My Car Smoke When I Start It? 7 Possible Reasons

Has it ever happened to your that you get into your car at the crack of dawn, and switched it on only to see smoke coming out of the car? Fortunately, this is rarely indicative of a serious problem in your car. But it can be quite mysterious and worrisome to those who don’t know what is causing the issue. That is why we have written this article to help you understand why your car smokes when you start it in the morning.

The car smokes that you might see when you start it are of multiple types. However, they are primarily two sources for them – the tailpipe and under the bonnet. Both problems have their causes. For example, smoke from the tailpipe is caused due to various liquids leaking into the combustion chamber like engine coolant or engine oil. However, the fumes that you see under the hood are a result of an external leak of engine oil or coolant. Fortunately, these problems are usually not serious and don’t affect performance too much either.

However, it is better to be safe than sorry. Understanding why these problems occur in the first place will help you fix the root cause and prevent this from happening again. Time to take a deeper look at these symptoms.

Exhaust fumes

Usually, when you see smoke coming out of the car (especially during start-up) it is from the tailpipe of the car. While this is more common, it is also less apparent as the driver doesn’t have a direct view of the tailpipe while in the driver’s seat. This type of smoke is generally caused by improper combustion.

Thin white smoke

Thin White Car Exhaust Smoke
Thin White Smoke | Image Credits: Unsplash

The most common form of smoke that you see coming out from your car exhaust is usually steam. This can be seen especially during cold mornings. The water in the atmosphere condenses and gets deposited in the tailpipe of your car. When the car starts, the hot exhaust gasses make this water evaporate and come out as steam.

The way to confirm this is that it would be thin white smoke that you see. Moreover, this smoke will disappear after a while. There isn’t much you can do about this, and it is perfectly normal for your car to do so. It does not pose any risk to your car. However, if the smoke does not disappear eventually, you might want to check out the other possible reasons.

Black smoke

Fuel Injectors
Faulty Fuel Injector | Photo Credits: Youtube – Ratchets And Wrenches

The second most common form of smoke observed is the black-colored one coming out of the exhaust of cars. There may be a couple of reasons for this. The first one is that a lot of unburnt soot has been deposited in the exhaust over time.

A second reason might be a problem with some sensors, the fuel system, or the air intake system. This causes a sub-optimal air-fuel ratio (which is rich) leading to unburnt carbon in the fuel. It may also cause black smoke in the exhaust. Since this is an indication of an underlying problem, unless that issue is rectified, the black smoke is not likely to stop.

Often this black smoke is seen in vehicles that aren’t regularly maintained.  Regular maintenance can easily prevent many of the problems leading to black smoke in the exhaust.

Blue/grey smoke

Engine Oil Cap
Engine Oil Cap | Image Credits: Pixabay

If there is oil being combusted in your engine, this might lead to a bluish-gray smoke coming out from your exhaust. Oil generally finds its way into your combustion chamber in one of two ways – either through the valves or through the piston rings. In either case, the problem isn’t too major. The first thing you will notice is a power loss (due to compression loss) and also fast engine oil consumption.

This problem does tend to snowball though as a lack of engine oil can lead to engine overheating or even some damage to the engine. Thus, in such cases, you should get the car checked up. Unfortunately, no matter the root cause, this is an expensive repair as there is significant assembly and disassembly involved. Moreover, entire parts may need to be replaced.

White smoke

Thick White Smoke
Thick White Smoke | Image Credits: Pixabay

Finally, the deadliest smoke that you might see from your exhaust is thick white smoke. As you learned earlier, this is generally caused by moisture content. In this case, the coolant is what leaks into the combustion chamber. However, the engine and the coolant circuits are sealed well. Hence, if this problem occurs it probably means the head gasket is blown. Or worse yet, the cylinder block might be damaged leading to a leak of coolant.

In such cases, the best thing to do is to switch off the engine and ask a technician to take it to their shop and inspect it properly. It is very dangerous to drive in this condition. There is a safety risk, and you might end up damaging the engine much more. Needless to say, this will also be a very expensive fix.

Under the bonnet

The problems discussed above are all related to the exhaust pipe. However, there is a chance of seeing that your car smokes when you start it from under the bonnet too. This is more apparent as the driver can see it while starting the car. At the same time, it is also rare. The causes for this are rather few and usually don’t mean anything serious.

Evaporating water or oil

Coolant Leak
Coolant Leak | Image Credits: Youtube – Gearheads

Sometimes, there is an external leak in the cooling or the lubrication system. This does not severely affect the engine. However, the leaking liquid sometimes falls on the hot exhaust system which leads to steam or smoke that you can often see under the bonnet.

Once this liquid evaporates, the smoke should disappear too. However, you would need to tighten some bolts/sensors or probably replace a cracked pipe to help solve the problem completely.

Engine overheating

Car Dashboard with Engine Temperature
Engine Temperature on Dashboard | Image Credits: Pexels

If you have some leaking engine coolant or oil, there is a high chance that your engine starts to overheat. This is because both these fluids have an important job in keeping your engine cool and operating at optimum temperature. An easy way to deduce if this is the problem that smokes up your car when you start it is to check the engine temperature indicator on your dashboard. You will even get a warning in case of high temperatures.

If you are certain that there are no leaks, then you simply have low levels of engine oil or coolant. Take a quick look at the fluid levels. If any of them are on the lower side, then you can just top them off to solve the problem.

If this still does not solve the problem, then you might want to flush and switch out the engine oil and coolant. Over time, several impurities get mixed up in them affecting their functionality. Thus, they need to be changed completely from time to time. This is usually done during the regular service checks.

Electrical Failure

Electric Current
Electrical Problems | Image Credits: Unsplash

Finally, one of the rarest reasons your car starts to smoke up when you start it is due to an electrical failure. You might want to check if all the electrical connections are fixed tightly or not. If there is some part of the electronics that have short-circuited, there is a high chance of heat generation. This heat generated leads to the melting of some plastic coatings which might cause some smoke under the bonnet.

In such scenarios, it is important to identify where the electrical problem is and then fix it accordingly. This should immediately rectify your smoke issue.

Final Thoughts

Seeing that your car smokes when you start it can be quite worrying. Hopefully, this article helped shed some light on where this smoke can be spotted and the possible causes for it. As you saw, most of these symptoms generally don’t point to anything very dangerous. However, it is important to get the underlying problem solved before it amplifies and snowballs into other problems. With any luck, the only smoke you will see out of your car is the common water evaporating from the tailpipe in cold weather.


Abheek is an Engineering student with a background in Automotive Engineering and Sustainable Energy Engineering. He has worked in Engine Development for a couple of years but is quite interested in Electric Vehicles too! In his free time, he likes to use his knowledge to help others with their car problems. Other times, he can be found following the sport of Formula 1.

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