Engine Temperature Warning Light Explained

The engine temperature warning light typically looks like a thermometer with 2 wavy lines at the bottom. Depending on the make of your vehicle, other symbols can include the letters ‘TEMP’, or ‘ENGINE OVERHEATING’.

The symbol should briefly illuminate on your dashboard when you start the car and go out shortly after the engine has started. This is perfectly normal, but if the temperature light comes on while driving, immediate action should be taken, particularly if the symbol is red.

Red Engine Temperature Warning Light

A red (occasionally yellow on some vehicles) engine temperature warning light that stays on or comes on while driving means there’s a coolant fault or your engine is overheating and requires immediate attention. Sometimes this warning light may flash.

Coolant, or antifreeze as it’s also known, consists of a mixture of water and ethylene glycol and constantly circulates the engine to keep it cool (see what is engine coolant for a detailed explanation). The usual cause is that there’s insufficient coolant in the system to keep the engine running at optimal temperatures.

What to do if the Engine Temperature Warning Light Comes on

If a red engine temperature warning light comes on, it’s essential that you stop and turn the engine off as soon as it’s safe to do so. An engine that has overheated to the point that it fails will almost certainly be irreparable and will require considerable expense to replace.

Leave your engine off for at least 20 minutes (ideally a little longer) before attempting to top up with coolant. Water in the coolant tank is pressurised and hot, so leaving to cool is essential. Ideally open the cap using a thick cloth in case hot water splashes onto your hand. Though a top up of engine coolant may be required on occasions a substantial drop in levels, or frequent topping up suggests there’s a leak that needs repairing.

Red temperature engine warning light
A red engine temperature warning light requires immediate action

Blue Engine Temperature Warning Light

Having a blue engine temperature warning light appear on your dashboard shouldn’t concern you anywhere near as much as a red one. This simply means that your engine oil is not up to optimal efficiency due to the low temperature. This may also apply to certain transmission types. Drive steady and avoid pushing the engine too hard until the light goes out. On certain models of vehicles, this engine temperature light may be green.

Engine Temperature Light on but not Overheating

If you’re experiencing problems with the engine temperature light coming on, but it’s not overheating, the likely cause is a faulty sensor. A sensor is used to constantly monitor engine coolant. This information is used by the computer to determine which settings to use for the engine, for example, if it is cold the engine will burn more fuel than when it’s warm.

Symptoms of a faulty coolant temperature sensor can be:

  • using more fuel (if more fuel is being burned because the computer thinks it’s cold)
  • temperature warning light stays on while driving but coolant levels and engine temperature are fine
  • smoke coming from the exhaust due to the incorrect fuel mixture being burned

8 thoughts on “Engine Temperature Warning Light Explained”

  1. Feroz

    Heat engne warning light kay kam karna padegs

  2. Hi Feroz,
    Check that you have sufficient engine coolant in the reservoir.
    Check the V-belt / serpentine belt is present, not lose or damaged.
    Check the water pump is working.
    Check that the coolant system is clean and doesn’t require flushing.
    If the engine doesn’t appear to be hot though the light is on, it could be faulty sensor.

  3. Sean

    Sometimes when i’m about to start my engine, the temperature light is red. But it disappeared when engine started. Is it because the engine is still hot compare to every morning is shows blue light?

  4. Hi Sean,
    It’s perfectly normal for the red engine temperature warning light to come on for a short period and then to go off once the engine has started. This is usually a simple bulb check. When the engine temp light is blue, it means the engine is not yet up to optimal running temperature.

  5. Richard

    Is this OK, even if the light stays on for 5 minutes or more on a warm day (only just bought the car). Or could it be a sign the thermostat is faulty?

  6. Hi Richard
    If there are no signs of your engine coolant overheating, then yes, as you say, it’s likely a sensor fault.

  7. Franck Grippon

    Hello, I was Driving my 2016 Nissan Rogue home from work on Friday. The temp light came on its white coolant levels are good, temp gauge is sitting at normal. It sat all night Friday and all Saturday I then drove it home from a buddy’s light is still on and white.

  8. Hi Franck,
    It’s likely a problem with the multi-function temperature sensor which operates the gauge, warning light etc.

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