Made from a mixture of water and antifreeze, coolant is a vital part of your car’s cooling system, which is designed to stop your engine getting too hot or cold.
Coolant circulates through the engine, absorbing the heat created by combustion, then releases it through the radiator. The antifreeze component also stops the coolant from freezing in cold weather, or overheating when it's hot.
If there’s an issue with the cooling system, the coolant warning light will come on. In this guide, we’ll cover how to identify this light and list its common triggers. We’ll also explain what you should do if your coolant warning light appears.
Get a free valuation
What is the coolant warning light?
The coolant warning light is a sign that there’s a potentially serious problem with the cooling system. The dashboard symbol normally looks like a radiator, a thermometer floating in water, or a combination of the two.
The colour of the light can be blue, amber, or red, depending on the severity of the issue. This follows the ‘traffic light’ system used for most dashboard warning lights:
- Blue is used to bring something to your attention.
- Amber warns of an important issue that should be addressed as soon as possible.
- Red indicates an issue that requires immediate attention.
Whatever colour light you’re seeing, it’s important to take the message on board. If you fail to heed a warning, you could seriously damage your car, leaving you with a hefty repair bill.
Why does the coolant warning light come on?
A low engine coolant level is the most common trigger for this warning light. Your coolant reserves will naturally deplete as you drive - but will drain faster if there’s a leak somewhere in the cooling system, such as in the hoses, radiator, or the pump.
Check underneath your car and around the engine for signs of a leak. Coolant is generally a bright colour, such as green, pink, or orange. So, it should be fairly obvious.
If the coolant level is just slightly below where it should be, you’ll see an amber light, reminding you to check the level, and get it topped up. If the level falls below the minimum, the red light will come on, indicating your engine is overheating.
Most cars have sensors that constantly check the coolant levels, pressure, temperature, and flow. This information is sent to the car’s computer so that it can make any necessary adjustments. If any of the sensors aren’t working properly, the computer will receive false information, triggering the coolant warning light.
The coolant warning light might also come on if there’s a problem with one of the cooling system components, such as the radiator, water pump, or thermostat. These parts can wear out, become blocked, or otherwise malfunction.
What should you do if the coolant warning light comes on?
-
Blue warning light
If the blue coolant warning light comes on, this usually means that your engine hasn’t yet reached an optimal temperature. Before you start driving, let your engine warm up. You should see the light disappear after a couple of minutes.
-
Amber warning light
If the amber warning light comes on, that’s a sign that your coolant level is low. Although the situation isn’t critical, you should still check your coolant levels promptly. Pull over in a safe place and let your engine cool down.
Don’t attempt to check your engine’s coolant while it is still hot, as you’ll run the risk of burning yourself. You should leave the engine to cool for around 30 minutes, then carefully open the bonnet.
Look around for signs of any coolant fluid leaks. If there are none, then check the coolant tank; its minimum and maximum levels will be marked to indicate how much coolant you need. If it needs topping up, do so carefully, wearing gloves - and using the correct coolant for your car. You can then restart your engine and check whether the warning light persists.
-
Red warning light
If the coolant warning light is red, that means your engine is overheating and you should stop driving immediately. If you carry on driving with an engine that’s too hot, you risk damaging it beyond repair. Once you’ve found a safe place to stop, switch your engine off and leave it to cool down. Again, check for coolant leaks and that the coolant tank is topped up.
Please note: If an amber or red coolant warning light persists after you’ve topped up the coolant and restarted the engine, take your car to the nearest garage, or call for roadside assistance immediately.
Coolant vs. antifreeze: How do they differ?
Coolant is made by mixing antifreeze, which is a concentrated liquid containing ethylene glycol or propylene glycol – with water. This is usually a 50/50 mixture, but a slightly stronger antifreeze concentration, such as 55/45, or even 60/40 is sold in some colder countries.
Although the terms ‘coolant’ and ‘antifreeze’ are sometimes used interchangeably, antifreeze is merely a component of coolant, which you put into your car’s cooling system.
Consequences of ignoring the coolant warning light
Like most dashboard warning lights, the coolant light should not be ignored. If you continue to drive with an overheating engine, you risk causing severe damage, or complete engine failure.
If the heat from the combustion process isn’t being taken away via coolant and other components of the cooling system, it will stay within the engine, which can cause parts to fuse together.
Once that happens, the only solution is to get a complete engine replacement, which can be very costly.
So, as soon as you see the coolant warning light, whether it’s amber or red, take action immediately to avoid damaging your engine beyond repair.
Regular maintenance and prevention
-
Regular maintenance is the key to keeping your cooling system working well. Check your coolant levels frequently; don’t wait for the warning light to come on.
-
Top up your coolant when needed, using the correct type for your car. You’ll see the minimum and maximum levels marked on the coolant tank, so you’ll know when it’s getting low.
-
Check for coolant leaks regularly. If there is a leak, you’ll see brightly coloured fluid either around your engine or under your car.
-
Keep your eye on the cooling system components. Watch out for issues such as a blocked radiator, cracked hoses, and a faulty fan. If you notice anything amiss, take your car to a mechanic for diagnosis and repairs.
-
You should also keep up with your regular services, so any potential issues and underlying problems can be caught early, saving you from pricey repairs.