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What To Do: When Your Coolant Light Comes On

Dashboard lights are such a familiar sight, particularly in more modern cars, that it is easy to ignore them until it is too late. Warning lights are there to do just that: warn you when there could be a problem with your car. This week, we take a look at your coolant light: when and why it comes on, and what you can do about it.

Combustion engines create power through combustion - that is, a series of controlled explosions. While these explosions are controlled, they still make a huge amount of heat. Your vehicle’s cooling system helps to control this heat, by pumping coolant throughout the engine.

When it comes on

Your coolant warning light will come on for a couple of seconds when you start your vehicle, before going out. Your vehicle computer system monitors the heat and levels of the coolant in your engine, to make sure that it can always control the temperature of the engine. The light will come on when the coolant is too hot. This is a sign that, for whatever reason, the coolant is unable to reduce the engine temperature enough to make it safe.

Why it comes on

Your coolant warning light has come on, or has stayed on once you have started the car, because either your coolant levels are low, or your coolant is overheating. If your coolant is low you probably have a leak, so you need to contact a garage as soon as possible.

What to do

If your coolant warning light illuminates while you are driving, safely pull over as soon as you can and turn the engine off for at least half an hour to let it cool down. Once the engine has cooled, you can use a cloth to open the radiator cap. The cap itself is designed to pressurise the coolant tank so that the water in it takes longer to boil. When you remove the cap, the water may well start boiling and release steam, so it is very important that your hand is covered to stop nasty scalding. If your engine still feels hot, do not attempt to remove the radiator cap; wait for longer, or call for help from a mobile mechanic. If the engine has cooled and you are able to safely remove the radiator cap, check the fluid levels in the radiator. If the coolant levels are low, you can create a short-term fix by topping it up with water. This should allow you to get to a nearby garage safely, without your engine overheating.

Remember that topping up with water is a quick fix that will get you safely to a nearby garage. If you don’t get the problem fixed, it is likely to happen again and, at some point, could cause serious damage.

For more tips and advice, follow Trust A Garage on Facebook or Twitter. Got a car problem? Get in touch with a trusted local mechanic.

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