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Why Is My Car Overheating?

Compact Cars, Bridgend

November 05, 2018 at 3:06 PM

Heat is an engine's enemy which is why every car comes with a cooling system built in. Unfortunately, there are certain conditions and mechanical failings that can cause an engine to overheat with potentially expensive repair work to follow if the problem isn't caught in time.

Although it's rare with modern vehicles, they are most likely to overheat in hot weather, especially if you find yourself in stop-start traffic or slowly climbing a steep gradient.

Overheating occurs when an engine's temperature exceeds the normal range, which is too hot to touch by hand, but significantly cooler with an effective cooling system in place. Any temperature that is upwards of 240° farenheit can cause long-term damage. 

You should see an engine warning light shaped like a thermometer on the dashboard or the temperature gauge spiking into the red zone to indicate that your engine is overheating. If you see steam coming from the engine area, you know you're in trouble and should pull over immediately and wait for mechanical assistance.


The reason your engine is overheating is because something inside the cooling system is preventing the absorption, transportation or release of heat. Below are some of the common causes for this to happen:

A Leak In The Cooling System

The cooling system comprises of the radiator, water pump, hoses, head gasket and thermostat housing. If there is a leak in any of these components, it can cause air to enter the system.

This air rises within the cooling system and as a result will form an airlock. Becuase this large air bubble is trapped, it prevents the coolant from circulating around the engine, and causes the engine to overheat.

If you know your way around this system and these parts, you might be able to find the leak and seal it yourself; however, you must always wait until the engine has sufficiently cooled down before investigating.

If you're not confident that you know what you're doing, it's best to get the expertise of a professional mechanic. 

Coolant Issues

If the concentration of coolant-to-water is not correct, your engine may have problems staying cool. This mixture keeps your engine cool in hot weather and prevents it from freezing during the colder months.

The coolant can solidify over the winter, causing a hard, gel-like mass which won't be able to circulate around the system. By flushing the system you might be able to fix this problem and add the proper ratio as recommended in your owner's manual.

Similarly, it can evaporate in the warmer months, making it seem like there's a leak. If this is the case, you just need to top the levels up and make sure they don't dip too far again.

Blocked Hoses 

If there isn't a leak and the coolant levels are correct, the next thing to check is the coolant hose. Sometimes mineral deposits like dirt or road sediment can build up in the coolant department and block the flow of fluid through the hoses.

Similar to the coolant issues, flushing the system and refilling the coolant tank could solve this issue.

Radiator Problems

Leaks, clogs or problems with the radiator fan all mean that heat can't escape your vehicle properly, which will cause the temperature of the engine to rise and overheat.

Damaged Water Pump

As the name suggests, the water pump helps to propel water and coolant through the cooling system. Any issue with the water pump can cause the engine to overheat.

Common water pump problems include leaks, shifting of the pump shaft and eroded impeller vanes.

Malfunctioning Thermostat

If you're lucky, your engine might not be overheating and you just have a dodgy thermostat that is giving false readings of the engine temperature.

Replacing a thermostat isn't something you can do at the side of the road, but when the engine is cool enough, you can check if it's working properly.

Remove the thermostat and reconnect the hoses without it. If the engine starts up and runs well without it, it was probably the cause of the dashboard light popping up or the temperature gauge going into the red.



If you start to notice that your engine is overheating, there are a number of things you can do to try and help cool it down:

Turn Off The Air Conditioning

Running the air conditioning puts an extra strain on your engine, so turning it off will reduce the amount of work it has to do. If it's a hot day, open the windows to try and get a breeze through to keep yourself cool.

Turn On The Heater

Although this will do very little to improve your personal comfort levels, turning on the heater will help an overheating engine because it transfers the heat from the engine to the cabin.

Rev The Engine In Neutral / Park

If you're in standstill traffic, put the car in neutral or park and rev the engine. This will make the fan and water pump work faster pulling more air and water through the radiator.

Don't Ride The Brakes

In stop-start traffic, try to crawl along slowly rather than sticking to the bumper of the vehicle in front and having to break repeatedly.

Brake drag increases the load on the engine causing it to heat up. If traffic is crawling, only move up when the gap between you and the vehicle in front gets too big.

Pull Over And Open The Bonnet

When you've tried all of the above and it's not making a difference, pull over to the side of the road, turn the engine off, open the bonnet and wait until things cool down.

If you start to see smoke coming from the bonnet, pull over straight away. Remember - don't open the radiator cap while the engine is this hot. If your engine has boiled over, don't add any water until it has significantly cooled down.


Sometimes, the engine can cool off quickly if you can get moving faster because more air will be pushed through the radiator, making the fan move quicker.

However, once your car overheats, expensive damage begins to happen. The longer it's allowed to overheat, the worse the damage is likely to get. So, if you're going to be stuck in gridlocked traffic, or unlikely to move very fast, it's often best to pull over and let the engine cool down.

Whenever you experience a situation where your car overheats, you should always get a professional mechanic to investigate the cause and provide a solution so that it doesn't happen again.

Category: Blog