Why Car Overheats?


Your car overheating is one of the most serious problems you’ll face as a vehicle owner. When your engine overheats, it may lead to irreparable damage or trigger a fire. What causes a car to overheat?

Cars overheat when the cooling system is compromised, and heat can’t escape quickly from the engine. A damaged water pump, broken coolant hose, damaged radiator fan, and reduced coolant volume due to leaks are common causes of overheating in cars.

The rest of the article will take a closer look at these reasons for car overheating. I’ll also cover what to do when your car overheats.

Top Causes of Overheating in Cars

If your car overheats, it’s likely due to any of the following causes:

Inadequate Coolant Level

The engine in your vehicle generates a huge amount of heat as it works. The coolant removes the bulk of the excess heat by absorbing heat from the engine before moving to the radiator to cool down. Once the coolant disposes of the absorbed heat, it cycles the engine to repeat the process.

Therefore, if your vehicle’s coolant level is lower than it should be, your cooling system is compromised. The result is higher temperatures for your engine. Over a typical commute, your engine may start to overheat. 

You should check your coolant levels regularly. It’s as simple as taking a quick look each time you check your oil or wiper fluid. Low coolant levels often signify a leak because you don’t need to top up coolant regularly like gas. If you suspect a leak, take your car to a technician.

Read: Temperature Gauge High But Car Is Not Overheating

Faulty Thermostat

The thermostat in your vehicle controls the flow of coolant. Once your engine reaches standard operating temperature, the thermostat valve will open up to push coolant through the engine. If the thermostat is faulty, the valve will stay closed when it should be open, causing the car to overheat.

Read: Why Your Car Won’t Heat Up

Broken Water Pump

The water pump is responsible for circulating the coolant across your vehicle’s cooling system. It’s known as a water pump instead of a coolant pump because earlier car models mostly used water to cool down the engine. Coolant is still water and ethylene or propylene glycol, but the pump remains the old name to date.

When the water pump is faulty, coolant may not circulate well across the engine or may not move at all. The result is an overheating engine even when your coolant levels are okay.

Read: How to Start a Car With a Bad Fuel Pump

Broken Radiator

The radiator is important in your car’s cooling system because it’s where the coolant goes to dissipate heat. It moves through tubes in the radiator, where attached fins in the tube collect heat from it. Air moving across the radiator dissipates the heat. If the radiator breaks down in any way, it may not carry out this function effectively.

Similarly, the radiator cap has to keep the cooling system pressurized. If the cap is damaged, the coolant will most likely escape the system leading to shortage. Any such damage will leave your engine at risk of overheating.

Broken Radiator Fan

Air flows over the radiator as you drive to remove the percolated heat transported in by the coolant. However, the radiator fan has to take over when your car is static. If the fan is damaged, your car may overheat as you idle at stops or move slowly through traffic. It will cool down again after you start moving.

Broken Head Gasket

Your car’s head gasket separates the engine block from the cylinder head. If it’s broken, oil can get into your cooling system, and coolant can get into your car’s combustion chamber. The result is a visible or invisible coolant leak, ultimately leading to overheating. If your head gasket breaks down, your vehicle may also start to extrude white smoke from the exhaust pipe.

Read: Car Full Service Cost // Whats included?

Common Signs of an Overheating Car

Your car overheating won’t damage your car’s components immediately. If you detect the signs of overheating and act quickly, you can reduce the risk of irreversible damage to your engine. 

Some of the top signs you should watch for include the following:

  • Steam coming from under your car’s hood.
  • Engine temperature gauge moving to critical/red/high (depending on vehicle brand).
  • Burnt or sweet smell coming from the engine (the burnt smell is leaking oil while the pleasant smell is leaking coolant).

Read: Car Diagnosis Cost

What To Do When Your Car Overheats?

Here are some steps to take if you notice your car engine overheating:

1. Turn Off the AC and Increase the Heat

Turning off the air conditioner will relieve the engine of some stress while turning the temperature control dial to maximum heat can draw away some heat from the engine. Wind down your glasses so you won’t feel too uncomfortable and pull over safely as soon as you can. The discomfort from the hot cabin beats the huge dent in your pocket from engine repairs.

2. Pull Over in a Safe Location As Quickly as Possible

Once you find a good location, pull over and turn off your car. Wait 15-20 minutes for the engine to cool down—or as long as it takes for the temperature gauge to go back to normal. While waiting, weigh your options for taking care of the problem.

You may call a friend for help or call the local mechanic. You may also need to call a tow truck, depending on the severity of the problem.

3. Top Up Your Coolant

Check your coolant level to see if it has dropped. Topping it off is a temporary solution that can save your engine in the short term while you mull over permanent fixes. However, topping up your coolant may not yield any results if there are other problems with your cooling system (such as a broken radiator or water pump).

4. Restart the Car

If you’re not expecting a tow truck, you can restart your car and slowly drive it to the nearest repair shop you can find. You may have to repeat the cool-down process a few times before you reach your destination, so keep an eye on your temperature gauge. If you’re far away from qualified mechanics, it’s best to park the car somewhere safe and wait for help to arrive.

Read: How Much Is an Inspection for a Car?

Other Tips for When Your Car Overheats

Don’t Panic 

Your car overheating doesn’t mean it’ll go up in flames in seconds. You don’t need to panic, swerve all over traffic, or slam your brakes while in the fast lane. Keep your eyes on the road and slowly maneuver to a stop to avoid causing an accident. A damaged engine is nothing compared to the risk of injuries and lawsuits.

Stop Driving ASAP

If your car overheats, you’re taking a big risk by keeping it on the road. While you may get to your destination with the occasional stop and start, there’s a high risk of causing significant damage by pushing the engine to the limits. Stop driving as soon as you can find somewhere to park.

Open the Hood After the Engine Cools

After you’ve pulled over, you may want to pop the hood as fast as possible. However, that exposes you to the risk of burns. The hot bonnet and the boiling steam can char your skin. Stay patient and wait for the engine to cool down (using the temperature gauge as a guide) before you open the hood.

Take the Car to a Repair Shop

If your car overheats once, topping the coolant and wishing the problem away isn’t a good idea. In most cases, the issue goes beyond coolant leakage. Take your car to a mechanic for inspection and get to the root of the problem. A qualified professional will find the main cause of the problem and recommend the best solution to solve it permanently and save your engine.

Final Thoughts

Cars overheat when the cooling system is compromised. If your car overheats while you’re driving, stay calm and pull over for it to cool down. Get to the root of the problem as quickly as possible and take steps to prevent reoccurrence in the future.

Most professionals recommend flushing your coolant when due and maintaining your radiator in line with your manufacturer’s recommendations.

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