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

33 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.

  9. My temperature warning lite was flashing rapidly red, heating was freezing, did notice water on my drive when I stopped. Does this sound like an expensive job? Any comments will be greatly appreciated …

  10. Hi Norah,
    It’s difficult to say. It might be a leaky hose which would be rather inexpensive to repair. Then on the other extreme, it might be a broken water pump, or going to greater expense, your engine’s head gasket. Until you have the fault diagnosed, there’s no way of knowing I’m afraid. I would avoid driving, perhaps only a short distance for repair as an overheated engine may seize and require a new engine – costing much more than the original repair.

  11. Simon

    hi, what does it mean when my engine temperature lights shows up when i on the car and disappears some seconds later. Note: I went to change some shocks and wheel alignment after that the 2 light high and low appears for some seconds and goes off.

  12. Stanley Feuer

    The temp light has come on twice on my wife’s car, once for a few seconds and once for a minute or so. It didn’t come on when we drove to another city on the interstate. Is this likely a sensor or something else? I don’t think the car is overheationg.

  13. Hi Stanley,
    Yes, it is likely the engine temperature sensor. The data from this sensor is sent to the ECU, which is then used to make adjustments to fuel, cooling system etc. You may notice changes in fuel consumption and how the car generally operates.

  14. In my case , when I start the car , the red temperature symbol shows up. Then turn off the engine and start again, it disappears. I don’t know if it’s normal or should I go to the rapair service?

  15. Hi Krishna,
    No, the red engine temperature warning light should go out when the engine starts. On some cars, there is a blue temperature light indicating that the engine has not reached has not reached optimal running temp. If it’s a cold start and the red temp light stays on, then obviously it’s not an overheating issue, but more likely a sensor fault. If it is a sensor fault, it’s a relatively inexpensive repair and worth getting fixed. A faulty coolant sensor can cause your engine to run rough.

  16. Danny

    my 2009 Nissan red light comes on a little bit after I start it. then it will go off and back on again. and so on and so forth. the coolant looks good. but the AC does get less cool when the light is on. and works fine when off. any thoughts

  17. Hi Danny,
    If you’re pretty confident that the coolant isn’t overheating, then it’s likely the coolant sensor.

  18. Sahib Adedayo Ganiyu

    I just topped my vw polo’s power steering oil and the next thing I see is the temperature light coming up after a start and remains there….what cold be wrong?

  19. Robin

    I have a Nissan Note light comes on but engine is not overheating and water levels are fine

  20. Prima Throop

    temperature sensor has been replaced and temperature light is still coming on .

  21. Hi Prima,
    Provided that the sensor was installed correctly and your coolant is at the required levels, you should have your car inspected for issues such as the water pump and drive belts. Your coolant may need flushing if it’s old and contaminated.

  22. Aufy

    I have a Toyota Sienta, when I drive over a long distance and high speed the red temp light flashes, when I stop and check coolant level I am able to add 1/4 liter, but when I drive at speed of not more than 90kph i am able to cover the same distance without the temperature warning light coming on, what might be the problem

  23. Hi Aufy,
    When you say you add 1/4 liter of coolant when driving over a long distance, how far is a long distance?
    In general, the coolant system is a sealed unit and when working properly, should rarely need topping up with coolant (50% antifreeze and 50% water).
    As you drive faster, the engine gets hotter and as the engine gets hotter, so does the coolant. The hotter the coolant gets, the more it expands and the more the coolant system comes under pressure.
    The result of this is that any weak areas of the coolant system may start to leak water.

    A leak can be either internal, such as a leaky gasket, or external, such as a hose failure or crack in the radiator, water pump etc. You can usually ‘get away with it’ for a while, providing that you keep checking coolant levels and top up when necessary. Leaks do have a tendency to get worse over time though. If you are getting white smoke coming from your exhaust pipe, it means water is getting into the engine block and mixing with the engine oil. This is a more serious condition that will need sorting quickly.

  24. Hi. I have a 2017 hyundai Santa fe. Out of no where my temperature gauge went all the way to the H and the red temperature light is comes on and the heater is not getting hot. But the car is not smoking or over heating and coolant level is fine. What are your thoughts on what the problem may be?

  25. Hi Elaine,
    It sounds like a thermostat problem. If the thermostat isn’t working properly, it may prevent water circulating to the heater core, hence the cold air.

  26. Saam

    Today I was on start mode in my honda vezel for 20 minutes with AC..and it was really hot day. Suddenly I felf AC was gone and only blower was workng..And I noticed temperature warnng light flashed in red. I suddenly stopped my vehicle, opened the bonnet and left it for 30 minutes. After 30 minutes, i started my vehicle then temperature waring light didnt appear and AC also worked as usual.
    What could be the reason for flashng the temperature warnng light in red and not workng the AC that time in my case? Is there a problem in the cooling fan or sensor fault?

  27. Dward

    I have toyota vios, before blue light temperature appears and go off when i start the engine..but now the red light temperature appears and go off when i switched on the engine.. is it a faulty Engine Coolant temperature sensor?please help..thanks

  28. Hi Dward,
    If the ambient temperature is already warm, then I’d expect the blue coolant light to go off quickly. The red temperature light going off when you start the engine is as it should do. It should be consistent though. I wouldn’t say it’s a problem, but keep an eye on it.

  29. Donald Monroe

    The blue coolant let comes on when I first start it for a couple mins then the orange system indicates orange light with an I and circle light stays on mechic was suppose to have checked it on June 29 but orange light stays on with no message

  30. Andrew

    Hello i have a ssanyong kyron 2008 my issue is after driveing a while my engine temp warning light comes on and guage goes to hot when i turn engine off and restart again everything goes back to normal. I have just changed radiator and all new coolant it is turbo diesel

  31. Hi Andrew,
    Provided everything is connected up correctly and there’s no leaks, it could be your thermostat.

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