What Causes a Car To Overheat?

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One of the most common reasons drivers find themselves stranded on the roadside is also one of the simplest: overheating. In the summer months especially, cars’ cooling systems can fail to do their job. Engines in most passenger cars operate at temperatures between 195°F and 220°F – when this spirals out of control, you can face some serious problems.

Today we’ll discuss how to spot an overheating engine, the most common causes for this problem, and what you can do about it, and how to prevent it from happening again.

What Causes a Car To Overheat?


Surprisingly, an overheating engine isn’t always easy to spot! Fortunately, there are plenty of telltale signs to watch out for:

  • An Overly-Hot Hood

One of the first symptoms you’ll experience when your engine overheats is a hot hood. It’s completely normal for an internal combustion engine to feel hot after operation, but if the bonnet feels extremely hot after a journey, you should get the vehicle checked out by a trusted mechanic. So how hot is too hot? When your car is working properly, you should be able to hold your hand on the hood for 10 seconds without burning your hand.

  • A Warning Light or High Temperature Gauge Reading

One of the more obvious signs of an overheating engine is seeing a warning light appear on your dashboard, or seeing the needle on your temperature gauge reach the demarcated danger zone. Although it’s an obvious symptom, bear in mind that warning lights aren’t foolproof. They take the car’s temperature from its coolant, so if you experience a coolant leak your engine is most likely overheating, but the dash light or temperature gauge won’t warn you.

  • Ticking Noise

An audible ticking noise coming from the engine suggests that your engine oil is failing to properly lubricate the engine. This happens when the oil overheats, suggesting that the engine has become too hot.

  • Leaks

If you notice a pool of liquid forming underneath your car, this could be the result of a coolant leak. It could also mean that the coolant has boiled and overflowed. Either way, chances are your engine is overheating.

  • Burning Smells

Another telltale sign of an engine that’s become too hot is the distinctive smell of burning oil, plastic, or rubber. As the engine gets too hot, rubber seals, plastic valves, and resin can begin to burn. The smell produced is often described as ‘hot’, and slightly sweet.

  • Stem
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As soon as you notice steam floating out of the hood, this is a sure sign your engine has overheated, and it’s time to pull over. Steam issuing from the engine suggests that the engine coolant has reached its boiling point.

  • Thumping Noises

Thumping noises coming from the engine while you drive could well be a sign of an engine that’s too hot. These noises occur when a valve becomes blocked, and the engine coolant is superheated. When this hot coolant comes into contact with cold coolant, a loud thumping noise is emitted.

  • Loss of Power

Major Causes and How To Fix Them

Below are five of the most common causes, and their solutions.

  • A Leaky Cooling System
  • A Blockage in the Cooling System

Ironically, these blockages tend to occur in cold weather. Poor quality coolant solidifies in cold conditions, causing a blockage in the system that prevents the coolant from properly circulating. Mineral deposits or a foreign object in the system can have a similar effect. This can usually be fixed fairly easily by draining and flushing the system, before replacing the coolant.

  • Low Oil

Another common reason why engines overheat is a simple matter of oil levels. As well as lubricating the engine, engine oil contributes to the cooling process of your car. In fact, as much as 70% to 85% of unused heat in the engine is removed through this oil. Because of its lubricating properties, engine oil also helps prevent excess heat in the first place by reducing the friction produced as the engine runs. This problem can often be remedied by simply topping up the oil to its proper level, but consistently low oil levels could be indicative of another problem. The cause could be:

  • An oil leak
  • Faulty valve seals leaking oil into the engine
  • Worn-out piston rings
  • Bear in mind that engines tend to consume more and more oil as they get older.
  • Broken Water Pump
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When it comes to overheating engines, another common culprit is a faulty water pump. This pump is responsible for circulating coolant around the engine, as well as moving it towards the radiator where it’s cooled by a forced air cooling fan. If your water pump is faulty, you can expect to see coolant leaking out, hear whining sounds as you drive, and steam emerging from the radiator. Water pumps are built to last, but they’re by no means infallible, and may need to be replaced after around 100,000 miles. Often, water pump faults are simply caused by a leak, which can be easily fixed with sealant. However, in some cases the entire pump may need to be replaced.

  • Hot Weather

Most modern cars are equipped with cooling systems that can keep the engine at a proper temperature even in the middle of summer – provided everything works as it should. However, classic cars are a different story. Cars manufactured before liquid cooling was widely deployed can overheat in high temperatures even when nothing is wrong.

Preventing Overheating

  • Keep an eye on your car’s temperature gauge and regularly check your oil levels – as discussed above, engine oil performs a vital function in cooling the engine
  • Keep your radiator clear of dirt, debris and bugs – a simple spritz with the pressure washer can significantly improve the radiator’s efficiency
  • Consider exhaust wrap – this coating can be wrapped around your car’s exhaust components, and helps to hold heat in the exhaust system, preventing it from dissipating towards the engine
  • Try to avoid rush hour traffic – stopping and starting makes your engine considerably hotter than running at constant speed, so avoiding this type of driving in the summer, as far as this is possible, can go a long way toward preventing overheating
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Problems Caused by Overheating

An overheating engine can cause several problems with your car:

  • The engine can cut out
  • Gaskets and seals can become damaged
  • You could lose power
  • Pistons and cylinders can become damaged
  • The metal in your engine can swell and become distorted from the heat
  • Overheating engines can put stress on the radiator

What To Do If Your Car Overheats On The Move

  • Pull over if you can

The safest and most effective way to cool your car’s engine is to switch it off, so pull over if it’s safe to do so when you suspect overheating. Next, pop the bonnet to help dissipate the heat – don’t pop the radiator cap, however, as the pressurized hot air and water inside could burst out and cause serious burns. When the engine has cooled down, check your coolant levels and top them up if you have supplies available – proper coolant is best, but using water is better than nothing. If possible, call for roadside assistance.

  • Take steps to minimise overheating if you must drive on

If pulling over isn’t an option, take the following precautions until it is safe to stop:

  • Turn off the air conditioning, and turn the heater all the way up. Car heaters utilize heat from the engine, so redirecting this into the cab is a great way to help cool things down – try to direct the hot air out of the windows.
  • Sitting in traffic, turn off the engine but keep the ignition on so fans continue to function
  • Keep a steady speed rather than stopping and starting if possible
  • Pull over and seek assistance as soon as it is safe to do so

Originally posted 2023-10-21 22:41:09.

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