The engine temperature light is one of the most important dashboard warning lights. A blue engine temperature warning light isn’t necessarily cause for alarm. However, if it turns red, this indicates that the engine is overheating - and immediate action is required.
In this guide, we’ll cover the purpose and appearance of the engine temperature warning light - and list some of its most prevalent triggers.
We’ll also explain the action you should take when you see each variant of the engine temperature warning light. Finally, we’ll share some tips to prevent your engine from overheating.
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What is the engine temperature warning light?
The engine temperature warning light may indicate that the engine is overheating, the coolant levels are too low, or the engine coolant is too cold.
It is usually depicted by a thermometer dipped in liquid. However, some car models will show a radiator symbol, or the word ‘TEMP’.
The specific meaning of this warning light differs depending on its colour:
Red: A red engine temperature warning light often appears when your engine is overheating. It may also indicate that the coolant level is below the minimum, or that another coolant fault is present.
Yellow/amber: This means that the engine coolant level is low.
Blue: A blue engine temperature warning light indicates that the engine coolant temperature is low. In some car models, the coolant temperature will also be displayed numerically, or by an analogue gauge.
Common causes for engine temperature warning lights
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Low coolant levels
When the engine’s coolant level is too low, this may cause it to overheat, triggering a yellow or red engine temperature warning light. Low coolant may be caused by a leak in the cooling system, a damaged water pump, or a blown head gasket.
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Faulty thermostat
The thermostat regulates the flow of coolant throughout the engine. If it gets stuck, the engine can overheat, triggering the warning light.
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Radiator fan malfunction
The radiator fan circulates air throughout the radiator to cool the engine. If it fails, this can cause the engine to overheat.
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Water pump issues
If the water pump cannot circulate coolant throughout the engine, it may overheat, triggering a warning light.
What to do when your engine temperature warning light comes on
The action required depends on the colour of the engine temperature warning light:
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Red
Whilst your car may technically be driveable, you should stop and allow the engine to cool for at least half an hour before resuming driving. Otherwise, you could cause costly damage to your car and its engine.
If the red warning light persists when you restart the engine, call your breakdown provider to tow your car to the nearest garage.
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Yellow/amber
When you see a yellow or amber engine temperature warning light, this means the coolant level is low. Pull over when it is safe to do so, check your coolant level manually, and top it up as soon as possible.
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Blue
This indicates that your engine coolant (or antifreeze) is too cold, which can stop the radiator from warming up. As a result of this, the engine can freeze, meaning it’s unable to start at all.
It’s important to note that this light will often illuminate when you start the engine in colder weather. It will usually only stay lit for a couple of minutes, then disappear once the engine has had enough time to properly warm up.
However, if the blue light persists for more than a few minutes, this could indicate a coolant issue, such as a leak.
Warning: Make sure you give the engine enough time to cool down before investigating the coolant levels. Otherwise, you could be sprayed by dangerously hot water.
If you are unsure how to identify a coolant leak, take your car to a mechanic for inspection.
Tips to prevent your engine from overheating
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Keep up with maintenance: Make sure you service your car at the recommended intervals. Your mechanic should perform coolant flushes, radiator checks, and thermostat inspections. If the hoses, belts, or radiators become worn, they should be replaced in good time.
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Keep up with oil changes: Fresh oil in the engine helps to prevent engine overheating and damage to components that are reliant on engine oil’s cooling and lubricating properties.
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Monitor coolant levels: Ensure that your car’s coolant reservoir is filled to an optimal level at all times. Also check that the ratio of coolant is appropriate for the climate.
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Adapt your driving habits: Avoid idling where possible; this can cause the engine to heat up with insufficient airflow. When driving in hot weather or heavy traffic, turn on your car’s fan or heater to direct heat away from the engine.
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Replace your car battery: After around three years of use, car batteries lose power, forcing the engine to work harder, which increases the risk of overheating. Make sure you replace your battery, spark plugs, and other electrical parts when necessary.
Can you drive with the engine temperature warning light on?
If the engine temperature warning light is red, you should stop driving for at least 20 minutes. If the light persists, call your breakdown provider to take you to the nearest garage.
You shouldn’t drive with a blue engine temperature warning light, either. Wait for the light to disappear, or have your car towed to a mechanic if it persists.
If you see a yellow engine temperature warning light, this indicates low engine coolant. Check the coolant level; if it is low, but still above the minimum, you can safely drive to the nearest garage. If it’s below the minimum, top it up; if you can’t, call for assistance.
What happens when you ignore the engine temperature warning light?
You shouldn’t ignore a red engine temperature warning light, as you could expose your engine to dangerously high temperatures that could severely damage your vehicle.
You should also avoid driving with a blue engine temperature warning light, as the engine could seize up. The engine system may develop cracks due to coolant expanding as it freezes. Without a steady flow of coolant, the engine will start to overheat, and may even explode due to pressure caused by blockages in the cooling system!