Car Engine Overheating: Here Are the Causes & What to Do When It Happens

An engine relies on its cooling system to keep its operating temperature stable. However, there may be times when the cooling system is unable to function as it should, which leads to overheating. An overheating engine will not only ground your car but could also cause permanent damage if you don’t take the right actions to fix it. That’s why we’re here to help you understand what causes an engine to overheat and what you can do when it happens.

Asian woman and car overheating

Reasons that Cause a Car Engine to Overheat

Your car’s engine cooling system is more than capable of cooling your engine down when it works properly. However, your engine can overheat when there are problems with the engine components or the engine’s cooling system. There are various reasons that can cause the engine temperature to rise above normal, such as a faulty engine coolant temperature sensor or a clogged radiator. Here are some of the most common causes of engine overheating.

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1. Faulty Thermostat

The thermostat functions like a valve that controls the amount of coolant that enters the engine. If the valve on the thermostat doesn’t function as it should, your engine might not be getting enough coolant which will lead to your car overheating. Besides overheating, signs of a faulty thermostat also include coolant leaks under your vehicle and frequent temperature fluctuations. If your engine temperature warning light comes on and off frequently, it’s a good idea to check your thermostat. 

2. Faulty Radiator Fan

The radiator fan blows cool air through the radiator fins to cool the coolant in the radiator. If the radiator fan is faulty, the coolant can’t dissipate the heat that it carries from the engine, leading to overheating. Since there is less air flowing into the radiator when your vehicle is at a standstill, your engine temperature might spike while you’re stuck in traffic. Here are common issues that can cause your radiator fan to fail:

  • Faulty engine coolant temperature sensor or sensor relay.
  • Problems with the fan motor such as a worn-out motor carbon brush.
  • Damage to the wiring.
  • Damaged or loose fuse.

3. Dirty or Clogged Radiator

Rust can sometimes build up and be sedimented in the radiator pipes. This will eventually disrupt the flow of the radiator coolant and reduce its ability to dissipate heat from the engine. In the long run, a clogged radiator can lead to the coolant leaking and even cause damage to the water pump.

Besides the coolant, air also needs to circulate freely through the radiator fins. When the fins are clogged up by dirt, leaves, or insects, the airflow is blocked. This prevents cool air from cooling down the radiator, which leads to your car overheating.

4. Broken Water Pump

The water pump keeps the coolant moving through the cooling system so it can absorb the heat from the engine. When the water pump is faulty, the flow of the radiator coolant can get disrupted, leading to overheating. Besides an increase in the engine temperature, a broken water pump can also cause the coolant to leak. A common issue with the car water pump is a worn-out impeller or a loose connection between the impeller and impeller shaft.

5. Leaking Head Gasket

The head gasket is the gasket that’s compressed between the engine block and cylinder head. One of its key functions is to seal the engine block and keep coolant and engine oil from mixing together. A leak in the head gasket could cause the gas from the cylinder to enter the cooling system. This gas then increases the pressure in the cooling system which can cause the coolant to be pushed out. Eventually, the coolant can get depleted causing the engine to overheat.

6. Leaking or Dried Up Radiator Coolant

Without enough coolant in the radiator, the cooling system is unable to get rid of excess heat in the engine. The usual causes of coolant leaking are a faulty water pump or leaks on the radiator, radiator hose, or water jacket core plug. If you don’t have coolant leaking but notice that your coolant level is always low, it could mean that your coolant is evaporating and drying up. This could be caused by a leaking gasket head or a faulty radiator cap.

7. Trapped Air in The Cooling System

Air bubbles can form in the cooling system when the head gasket fails to keep the gas from the cylinder out. However, air bubbles can also be trapped when you perform an incomplete radiator fill-up or improper coolant flush. When you have low levels of coolant in the radiator, it can cause the water to evaporate and produce air bubbles. If you face this issue, you can send your car to the workshop for a radiator bleed to get all the air out.

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Car engine temperature sensor gauge

Signs that Your Engine is Overheating

If left unchecked, an overheating engine can cause irreparable damage. That’s why it’s crucial to get your car checked if you notice any signs of overheating. Here are some signs to look out for:

  • The engine temperature gauge on your dashboard rises above the normal temperature. Some cars only have an engine temperature warning light that lights up when the engine temperature rises above normal.
  • White smoke or water vapor rising from the engine bay.
  • A burnt or acrid smell from the engine. A burnt smell is usually a sign of leaking engine oil while leaking radiator coolant usually smells sweet.

What to Do When Your Engine Overheats

If you notice that your engine temperature warning light is on or there is smoke coming from the front of your car, chances are your engine is overheating. To help you in this situation, here are some steps you can take.

1. Stay calm

The most important thing to do when your car overheats is to not panic. If you’re driving on the road, don’t slam on the brakes. Instead, take note of your surroundings and slowly pull your car over to the side of the road so you can assess the situation. Turn off all electrical components while you do this to minimize the strain on your engine.

2. Stop at a safe location and turn off your engine

If your engine temperature warning light is on or the temperature gauge needle is in the red zone, don’t continue driving. Driving while your engine is overheating can result in bigger damage to your engine or even cause a fire. Instead, pull over at a safe location. If there’s a workshop or parking lot nearby, you can park there instead of at the side of the road. Also, turn off your engine and all electrical components as they can cause further stress on the engine. 

3. Don’t open the bonnet immediately

Once you have stopped, wait until the engine has cooled down or for the temperature gauge to return to the normal level before opening the bonnet. If you open the bonnet too soon, you could risk burning or hurting yourself as there could still be hot vapor or smoke waiting to escape.

4. Add water and get your car checked

After your engine has cooled, you can top-up water in the radiator as a temporary fix. This may just be enough to get the engine running for a short while. If you’re able to start your car after the engine has cooled down, take it to a nearby workshop immediately. Just be sure to drive slowly and keep an eye on the temperature gauge. If the temperature spikes again, pull over and let your engine cool down before continuing your drive. If you’re unable to start your engine, do get a tow truck to tow your car to the workshop. By having your car checked at a workshop, you can properly identify the reason your engine is overheating and fix it before it develops into a bigger problem.

Refilling Radiator Coolant

Tips To Prevent Engine Overheating

By taking care of your car, you can minimize the chances of it overheating or breaking down. That translates to you having a safer car and reduced repair costs. To prevent your engine from overheating, here are some simple things you can do:

  • Regularly check your coolant reservoir and make sure that it’s sufficiently topped off.
  • Check the radiator to see if it’s clogged as debris (dirt, leaves, insects, etc.) stuck on the radiator fins can block air flow into the radiator. 
  • Check the radiator cap and make sure that the spring in the cap isn’t loose as a loose cap won’t be able to maintain the proper pressure level in the radiator.
  • Check your timing belt, as a faulty timing belt can cause a host of engine problems including overheating. Some signs of a faulty timing belt include ticking or rattling noises as well as poor engine performance.
  • Don’t skip your car’s scheduled maintenance. During this scheduled check, your mechanic will check your car’s engine, fluid levels, and other components to make sure everything is alright. If there are any issues, you can get them fixed before they turn into something serious.

Now that you know what can cause your engine to overheat and how to prevent it, we hope you’ll be prepared if it ever happens to your car. If you’re looking to buy a used car or even sell your own car, do check out CARSOME for more information. At CARSOME, we put all CARSOME Certified cars through a strict 175-point inspection to rule out major accidents and flood damage. We also professionally refurbish our cars to give them safety beyond standards, complete comfort, and refurbished aesthetics.