Steam Or Smoke Coming From Radiator Cap: What To Do?

The radiator of your vehicle is one of the components in your vehicle that must give you problems first before you even think of it. The cooling system of your vehicle is made up of a thermostat, radiator, and water pump. If your radiator cap has a problem, it will alert you. 

So what do you have to do if there is steam or smoke coming from your radiator cap? What you have to do is pull over and then turn off your engine. You have to let your engine cool off first before diagnosing what the problem is. 

You might also have some experience with your radiator cap. A steam or smoke that is coming out of your radiator cap is not normal. You should immediately check your vehicle and you have to let the engine cool first. 

In this article, we will be talking about steam or smoke coming from your radiator cap. A lot of car drivers have always been asking if such an event is normal. You can always have your vehicle checked at so that you will know what to do. 

If you have experienced steam or smoke from your radiator cap, this article is definitely for you. Let us get started. 

Steam Or Smoke Coming From Radiator Cap

Why Is Steam Coming From The Radiator Cap?

A lot of car drivers have been experiencing steam that is coming out of their radiator caps. This situation is not normal. Some people might think it is normal to find steam from their radiator cap, but it is not normal. 

You might have a shot in your cap gasket, or your radiator neck might be worn. The cap can also not be sealed. Steam coming from your radiator cap might mean just something minor, or it can mean something more serious. 

Is Steam Supposed To Come Out Of The Radiator?

It depends. The steam will rise, and it will enter each heating radiator through a single pipe. It will push air out of your radiator with the vents. Condensate will return to the boiler through the same pipe, and it will then pass out through a particular passage in the radiator control valve. 

This is regular steam, but there is also steam that is not normal. An issue can cause it with your radiator cap or something else. 

What To Do If The Radiator Is Steaming?

If you are in a situation where your radiator is steaming, do not think you are helpless. Instead, take control of the situation and follow the steps. Here is what you can do. 

1. Pull Over

If you see steam coming out from under your radiator, immediately pull the vehicle over. Driving the vehicle with the steam coming out might be dangerous, depending on the steam’s real cause. So stop driving and pull over as fast as you can. 

2. Turn AC Off

The next step is to turn off your air conditioning and then turn the heater on. 

3. Turn Off Engine

The next step is then to turn off your engine. 

4. Cool The Engine

Leave your engine to cool down. After your engine has cooled, you need to open the hood. 

5. Check Coolant Level

And then check the level of your coolant. 

Why Is My Radiator Smoking From The Cap?

The smoke you’re referring to is steam. If you have the radiator cap off the radiator, the water will not be under pressure, and it will then come to a boil. There are also the issues with a blown head gasket or a cracked water passage or jacket. 

It can also be a bad thermostat, resulting in a boiling coolant or white smoke. You need to check where the white smoke is coming from. If the white smoke comes from your engine compartment, you might be leaking coolant from your radiator. 

It can also come from a hose or a gasket. It can also be a gasket by the water pump, or it can also be a hole in your radiator. If you find out that it is in your radiator, you can buy something that will plug the leak at your local parts store. 

Is Smoke Supposed To Come Out Of The Radiator?

The radiator will prevent overheating. This is done by cooling the fluid flowing around the engine block so that it can dissipate the engine’s heat. 

If you see smoke from your radiator, it can be a symptom that your radiator is not doing its job. And the result can be an overheated vehicle.

What To Do If The Radiator Is Smoking?

One of the first things you will notice if your cooling system is having a problem is that white smoke will come out of your radiator. It can come out under the hood, or it can puff a large quantity in your tailpipe. 

If there’s smoke coming out from your radiator, you need to pull over immediately and shut off your engine. This can be a sign that your vehicle is overheating. 

White smoke coming out of your tailpipe indicates an internal coolant leak, allowing the coolant to be burned in your engine. It will then be dismissed through an exhaust system. Your vehicle will then overheat. 


In summary, car drivers have experienced that steam or smoke is coming out of their radiator cap. A lot of car drivers have been in this situation. 

The reason can be severe, and it can also be minor. You need to find the cause to fix the problem.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more