Why is my car smoking under the hood? — causes and fixes

You don’t have to be an expert to conclude that something’s seriously wrong with your vehicle if smoke starts coming from under the hood. This can happen while driving, or even while trying to start the car, and it might leave you completely confused.

Naturally, you’ll be asking yourself – why is my car smoking under the hood? Your car is smoking under the hood due to the vehicle burning engine oil, leaking gasket seals, or coolant leaks. While these are some of the most common scenarios, we’ll also discuss some other possibilities to get you prepared for this situation.

What does smoke from under the hood mean?

If you experience smoke coming from under the hood, it can be truly frightening at first, since that’s where your engine is. However, it doesn’t necessarily mean that something’s off with your engine. You can stop driving and look at the gauges on the dashboard first to try and figure out what’s happening.

If you notice a temperature gauge drastically fluctuating, and your car overheats and won’t start, it means there’s probably a leak in the cooling system. It can also be an engine oil leak, so it’s dangerous to keep driving.

However, if your engine isn’t overheating, it can be one of the minor causes. If you only notice smoke from under the hood when starting the car, it can be due to overheating the starter. Especially if it takes longer to crank your engine, this could be the culprit and you might not be able to start it at all.

When driving, make sure to check the gauges first. Along with the temperature gauge, the “check engine” light should also appear in case there’s a problem with the engine and its cooling system. Even if it’s not a big problem with the engine, you should consider towing your car to a mechanic shop, just to be safe.

Common problems that lead to smoke under the hood

A lot can be concluded about the nature of the problem by looking at the color and even sensing the smell of the smoke. However, black smoke usually exits through the exhaust, and white smoke or steam is the most common in case your hood smokes.

Sometimes, there’s also a gray or even blueish smoke under the hood, so let’s take a look at the main reasons behind it:

• Car fluids leaking onto engine parts or exhaust manifold
• Leaking head gasket
• Cracked cylinder head
• Leaking coolant
• Engine oil leaks

The most “harmless” option is if car fluids like engine oil or coolant are leaking onto the hot parts in the engine compartment. If some oil leaks onto the exhaust manifold, it will burn as the car reaches operative temperature and it will result in steam from under the hood.

This shouldn’t be normally happening, so make sure to inspect your car if you find these leaks to be the culprit. Even though it won’t hurt your engine as much as a leaking head gasket, you should still find the source of the leak and fix it.

Hood smoking due to leaking head gasket

If your engine’s head gasket has cracked and is leaking, you’ll have limited time to react and try to fix the problem. The head gasket makes a seal between the engine block and the cylinder head, and it keeps the engine oil and coolant from escaping the block.

However, its seals can sometimes degrade over time due to heat generated by the engine and constant friction. If that happens, you’ll end up with a blown head gasket and engine oil or cooling liquid might reach and enter the cylinders.

In this case, the oil or coolant burns with the combustion mix and it results in excessive white smoke. It leads to engine overheating, and a “check engine” light appearing on the dashboard. It’s one of the worst situations where your hood smokes, and could result in a complete engine rebuild if you don’t repair it on time.

You might be able to temporarily use a head gasket sealer to prevent the oil from entering the cylinders until you drive to a mechanic and replace the gasket.

Cracked cylinder head problems

A cracked cylinder head might initially appear similar to a blown head gasket. Some of the main symptoms are the same, including white smoke appearing from under the hood and from the tailpipe, and overheating.

A cylinder head consists of different valves that let air into the cylinders and at the same time, it allows the exhaust gases to go out. It seals the upper parts of the engine cylinders into the block connected with the head gasket in between.

So, any cracks in the cylinder head might lead to coolant entering the combustion chambers and burning out as smoke under the hood.

Leaking coolant

If there’s a leak in the cooling system, you might see white steam coming from under the hood. It’s usually accompanied by a sweet coolant smell, so that’s a clear sign of what’s happening. Coolant could be leaking from the seals or radiator hose.

Radiator tubes and hoses can get cracked due to high mileage or even corrosion, which might cause coolant leaks. It also happens if the water pump fails, or if your head gasket gets blown. There are two possibilities here – either the coolant leaks into the cylinders and causes the smoke, or it leads to engine overheating.

A faulty radiator hose could also sprinkle the coolant over the hot engine parts, resulting in white smoke coming from the hood.

Engine oil leaks

Engine oil lubricates the moving parts inside the engine block, and it also aids in cooling down the engine. So, if there’s a leak, chances are that you’ll see white smoke coming from under the hood due to overheating.

Also, you should check if you’ve properly changed the oil previously since even a few drops of oil leaking around the engine or onto the exhaust manifold can burn out. So, it might lead to smoke coming from the hood, and you could think it’s something more serious while it’s harmless.

Oil spilling over the engine can be the worst scenario, and it often happens due to a cracked or blown head gasket.

How to fix a smoking engine?

The first thing you should do if you notice white smoke coming from under the hood is to come to a safe stop. Wait until the engine cools down and pop the hood open, and look for fluid leaks. You should also consider the temperature gauge and “check engine” light if it appears.

If your car is overheating, tow it to a mechanic for a detailed inspection. The worst-case scenario, and also the most expensive one, is if you have a blown head gasket or a cracked cylinder head. It takes replacing the components for your engine to work properly again without burning fuel or the coolant.

Looking for a potential oil spill can save you the trouble if you overfilled the tube, and you should have your mechanic inspect your cooling system and look for oil leaks.

Our take

If you are not much of a car guy, the best thing you can do in case your hood smokes is to stop driving and tow the car to a mechanic. Hopefully, this guide answers the question of “why is my car smoking under the hood” and gives you some ideas on what might be the culprit.

Still, don’t try to do much fixing on the spot if you don’t have the right tools at hand, and leave it to a trusted mechanic to find the cause.