Car Overheats When Idling: 7 Causes & Step-by-Step Guide To Fix

You’re sitting in traffic or waiting at a stoplight, and your car’s temperature gauge starts to climb. Before you know it, your car overheats when idling. But why does this happen? So, in this article, we will delve into the seven main reasons behind this common problem and give you some helpful advice on what to do about it.

Car Overheats When Idling: 7 Common Reasons

There are several reasons why your car might be overheating when idling. Here are seven of the most common.

Damage radiator fan

Your car overheats when idling could be due to a damaged radiator fan. Usually, a radiator fan is a key component that helps your car’s engine remains cool even though it generates a lot of heat. So, if this radiator fan breaks or starts malfunctioning, it can’t pull sufficient air over the radiator, leading to heat building up in your engine

 Radiator fan

Poor thermostat

Another reason is the thermostat. In general, it will help control the coolant flow to your engine. When your car’s engine reached a high temperature, this thermostat will open to let the coolant flow and cool your engine, keeping running smoothly. Thus, if the thermostat gets stuck or in bad condition, coolant cannot reach your engine. And this leads to the buildup of heat in an engine.

A faulty radiator cap

The reason may be the radiator cap. When it is working correctly, it helps keep the right amount of pressure in the cooling system, usually between 13 to 16 psi, depending on what kind of car you have.

If the cap isn’t sealing right or is damaged, it can’t keep the pressure at the right level. When this happens, the cooling system doesn’t work as well. The coolant can start to boil at a lower temperature than it should, which means it’s not as good at absorbing heat from your engine.

Check radiator

Radiator blockage

Furthermore, the problem could be caused by a clogged radiator. Over time, your radiator can build up rust and other debris, and that prevents the coolant from flowing smoothly. Therefore, it cannot effectively absorb and dissipate heat for the engine, causing your car to overheat.

Head gasket failure

In addition, the head gasket in your car can also be the cause. Normally, it is located between your engine block and the cylinder head, helping to keep the coolant from leaking out, causing engine leaks.

However, if the head gasket is damaged, the coolant will leak out and seep into the engine and then the amount of coolant will not be enough and keep your engine cool. From there, your car will easily get hot when idling.

Water pump failure

The water pump is the heart of your car’s cooling system. It ensures that coolant circulates through the engine and radiator, acting as a medium to transfer heat from the engine to the radiator, where it’s cooled down.

But if it isn’t pumping correctly, the coolant can’t flow as it should, creating an imbalance in heat distribution, leading to your engine can start to overheat, so, the system it supports begins to fail.

Car water pump

Coolant problems

Finally, the cause can also be coolant issues. If your coolant level is too low or not enough to dissipate heat. What’s more, if you use the wrong type of coolant, not is right for your car’s model, resulting in not absorbing heat effectively. Thus, causing your car to overheat when idling.

Read more: How to Stop Brakes from Squeaking Without Taking Tire Off !

How To Fix An Overheating Car

Has your car been playing up, showing signs of overheating while idling? First things first, don’t panic. Here’s a step-by-step guide to help you troubleshoot and possibly fix the problem. However, keep in mind that while some of these fixes can be done at home, others might require the expertise of a professional mechanic.

Step 1: Diagnose the problem

The first step to fixing an overheating car is to diagnose the problem. Identify the symptoms, when they occur, and try to pinpoint the cause. Is it only overheating when idling? Does the temperature gauge rise rapidly, or does it creep up slowly?

Step 2: Inspect the radiator fan

Once you’ve diagnosed the problem, start by inspecting the radiator fan. If your car overheats when idling, a damaged radiator fan might be the cause. So, you should check if the fan is working when your engine gets hot. If it’s not, you may need to replace it.

Step 3: Check the thermostat

If the fan is working fine, move on to the thermostat. If it’s stuck closed, it might prevent the coolant from reaching your engine, causing it to overheat. Alternatively, you might notice the upper radiator hose remains cool, even as the engine heats up, indicating that the coolant isn’t reaching the engine. So, you should take your car to a professional to replace it.

Step 4: Examine the radiator cap

A faulty radiator cap can also cause overheating. If the cap isn’t sealing correctly, it can’t maintain pressure in the cooling system, reducing its effectiveness. Inspect the cap for any visible damage or signs of wear. This could include a broken seal, cracks, or other deformities. If you see the listed signs, you should replace them.

Step 5: Flush the radiator

Over time, your radiator can become clogged with rust and debris. In this case, you can flush the radiator can help remove any blockages and restore the cooling system’s efficiency.

Step 6: Check the head gasket

A failing head gasket can cause coolant to leak into your engine, leading to overheating. If you suspect this is the issue, you might notice coolant loss without any visible leaks, white smoke from the exhaust, or milky oil. We highly recommend you consult a professional mechanic if you suspect a head gasket failure.

Step 7: Inspect the water pump

If the water pump isn’t working correctly, it can’t circulate the coolant, leading to overheating. Listen for any strange noises from the pump or look for visible leaks.

Step 8: Assess the coolant

Finally, check the coolant. If the levels are too low or you’re using the wrong type of coolant, it can cause your engine to overheat. So, you need to make sure you’re using the correct coolant for your car and that it’s at the proper level.

Remember, while it’s possible to diagnose and fix some of these issues at home, it’s often best to consult a professional mechanic to ensure the problem is correctly identified and remedied.

Car overheating

Do’s and Don’ts for Overheating Your Car

Here, we provide some tips on what to do and what to avoid when your car is overheating:


  • Pull over safely: As soon as you notice the temperature gauge creeping into the red or steam starts billowing from your hood, it’s time to find a safe place to pull over. Driving while your car is overheating can cause significant and possibly irreparable damage to your engine.
  • Turn off your engine: Once you’re safely off the road, turn off your engine, allowing your engine to start cooling down.
  • Allow your engine to cool: Resist the urge to pop open the hood immediately. The engine and its components will be extremely hot and potentially dangerous. Instead, allow your engine to cool down naturally for at least 15-30 minutes.
  • Check the coolant levels: Once your engine has cooled down, check the coolant level in the reservoir. If it’s low, there’s a reason why your car overheats.
  • Call for help: If you’re unsure about what to do, don’t hesitate to call for professional help.


  • Don’t ignore the signs: You should notice If your car starts showing signs of overheating, such as the temperature gauge moving into the red zone or steam coming out from under the hood. Continued driving can turn a potentially minor and easily fixable issue into a major, costly problem.
  • Don’t open the radiator cap while your engine is hot: It might be tempting to open the radiator cap to check the coolant or relieve pressure, but doing so while the engine is hot can cause boiling coolant or steam to spray out, risking severe burns.
  • Don’t pour cold water over the engine: It might seem logical to try to cool an overheated engine with cold water, but the sudden temperature change can cause engine components to crack or warp.


While idling, a car overheats can be a sign of several problems, from a broken radiator fan to coolant issues. Understanding these potential causes can help you identify and address the problem more quickly. Remember to always consult a professional mechanic if you need help with how to fix an overheating car.


  1. What might lead a car to overheat while it's idling?

    One common issue that might result in a car overheating while idling is a malfunctioning cooling system. If elements such as the radiator, water pump, or fan belt aren't working as they should be, this could cause the engine to risk overheating.

  2. Does overheating ruin an engine?

    Yes, severe overheating in an engine might lead to deformation and warping of cylinder walls or pistons. This can disrupt the seal between the piston and the engine. Consequently, oil might bypass the piston rings and enter the engine, where it can cause the oil to burn.

  3. How long can a car get too hot before damaged?

    Overheating can cause permanent damage to a vehicle in as little as 30-60 seconds. Hence, it is crucial to respond promptly upon noticing any signs of overheating. Ignoring these signs might lead to issues such as coolant leaks, damaged radiator caps, or an improper cooling fan.

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