Auto Repair Help

by Mark Davidson

The engine overheats or boils over. The temperature gauge reads higher than normal or the instrument panel “hot” light is illuminated.

The most common cause of an engine overheating condition is a defective thermostat. However, there are numerous items that can cause an overheating condition. Coolant loss will also cause an overheating condition. If you are experiencing coolant loss in the form of a leak, refer to the “Coolant Loss” symptom on this site. If the vehicle overheats and has excessive white smoke from the tail pipe, refer to the “Excessive Smoke From Tail Pipe” symptom (also on this site).

You should start your diagnosis with a visual inspection of the cooling system. Ensure the coolant level is at the proper level. Do not remove the radiator cap when the engine is hot! Inspect for warped belts and leaking hoses. If the engine overheats a few minutes after start up, the most probable cause is a defective thermostat. If the engine overheats after several miles of driving or only overheats at low speeds, you should inspect the cooling fan operation and radiator. On vehicles that use an electric cooling system, ensure the cooling fan is coming on at when the engine reaches operating temperature, usually between 195F – 220F. Let the engine idle with all of the accessories in the off position (such as A/C). Monitor the engines temperature by observing the temperature gauge. The cooling fan should automatically come on prior to the gauge reading hot. If it does not, promptly shut the engine off. If the vehicle is equipped with air conditioning, turn it on and observe the cooling fan. If the fan comes on, the most likely cause is a cooling fan thermostatic switch. If the fan does not come on, further diagnosis of the fans electrical system will be necessary.

On vehicles with a conventional radiator fan, inspect the fan for damage. Ensure the fan clutch is operating properly. Have an assistant turn the engine off while observing the fan. The fan should only spin for about 2 seconds after the engine is shut off. If the fan continues to spin for several seconds after the engine is shut off and the engine only overheats at low vehicle and engine speeds, fan clutch replacement may be necessary. If the cooling fan operates properly, inspect the radiators external cooling fins for excessive debris, such as bugs and dirt. When the engine has cooled down, remove the radiator cap and inspect the inside of the radiator for excessive scaling. The tubes that run accross from one tank to the other should be clear of build up. If the radiator is not equipped with a conventional cap, it may be necessary to remove one of the radiator hoses to perform an internal inspection. You should do this when the engine is cold. If necessary, the radiator can be removed and inspected by a radiator shop that will provide advice. A radiator that is plugged may require a “Rod Out” to restore proper operation. If the radiator, cooling fan, coolant level and thermostat are in proper working order further diagnosis will be necessary. It is possible that the impeller on the water pump is damaged or the vehicle has a blown head gasket or cracked cylinder head. White smoke from the tail pipe is a key indicator of such a failure.

Use extreme caution when working on the cooling system. The cooling system is under pressure when hot and can cause extreme burns if opened when hot. Use caution when working around hot or rotating engine parts. On vehicles with electric cooling fans the cooling fan starts automatically. Keep your body away from the cooling fan at all times. Radiator flush agents may be an aid in removing scaling from the radiator. Use these products as per the manufacturers recommendations.

Continued on Part 2

(Mark gave up on sports when the Browns left Cleveland and now spends his Sundays working under a shade tree in the back yard tuning his son’s soap box derby car.)

95 responses to “Diagnose Engine Overheating”

  1. william says:

    engine still overheating after replacing heads,headgaskets thermostat and has a new raditor and cap’ only thing i having replaced is the water pump itself.please help me with this problem.

    • Luis says:

      Check your oil levels. If oil type is right (10w30 or whatever your vehicle requires) then check all the hoses. If all the hoses are good (no bends, kinks, collapses) then double check your coolant levels and that correct coolant type and blend are in your vehicle. After this, make sure you installed the thermostat with the air valve in the up position (some thermostat do not have this, google for further explanation). After that assuming your head, gaskets, radiator and cap have all been replaced, check the belt (engine off of course) that runs your water pump; check if it is loose (should only give about 1/2 inch of play. Wether it’s loose or not, at this point you should probably replace your water pump and belt at the same time. I understand this is a lot of work, but I believe that’s the culprit. If you wanted to procrastinate this potentially incorrect diagnosis, you could flush your cooling system with a kit or a shop to make sure that won’t be an option in fixing your overheat condition. Otherwise just make sure you nail the timing from start to finish and if the timing is off once your finished, don’t run the car (if it will run at all) until the timing is corrected. Best of luck!

      • willy panaligan says:

        hi William check the installation of thermostat regarding its power supply, since if something wrong the thermostat will not open and it will restrict the cycle of coolant in cooling system of the car

      • Robert says:

        I have a 2000 3.9l dodge Dakota I’ve changed out my water pump tstat clutch fan, flushed all the hoses! It drives fine for a couple of days then overheats Then it’s fine again for a couple of days! This all started when I changed the water pump! Can someone please help!

  2. okumu says:

    Hi William, Please try and check all the radiator hoses followed by the water pump

  3. […] I'd take a look at this: Diagnose Engine Overheating – Auto Repair Help If turning the heater on makes a noticeable difference, the radiator becomes a likely source of […]

  4. Ahmed Soorma says:

    I just had the radiator removed from vehicle and found that one of the ends at the radiator metal body had a small section (ribbed) was slightly loose.
    Had the radiator body internally cleaned and then used solder mix with “Magic Epoxy” and spread it over the affected area.

    Replacement cost of that end is the next solution if the radiator leaks again.

    Have the radiator checked by a good workshop who will not chisel you off.

  5. john sooner says:

    My engine is overheating the thermometer does not go off scale but is high. The electric fan runs does mean the thermostat does not need changing. I note you recommend changing the thermostat as a first diagnostic action but is that even if the fan works, I do get Blue smoke but not exceessive

  6. terry bell says:

    I have a Pontiac astex it is over heating new water pump new radior new thermostat new radior cap there is no white smoke from tail pipe it dosnt use water no leakes can you tell me what is next?

  7. terry bell says:

    fans are also working

  8. Josh Cataldo says:

    I have a 2000 Cadillac Seville SLS 4.6L. The car has 175,000 miles on it.
    The car over-heats while driving faster and cools when driving slower but still stays at the half-way point on the gauge. The thermostat, lower and upper radiator hoses have been replaced and the fan does turn on. The car still run dangerously hot. Any ideas?

    • Josh Cataldo says:

      I did do the chemical block test. Both times the fluid chemical did not change color. The fluid chemical stayed blue.

  9. tom says:

    my alarm says “engine hot turn off A/C and idle enigine”
    I changed the thermotat no help. it has no signs of leaks
    and as long as I am moving its fine but when i stop i have to turn the car off once i start moving temp goes down fast

  10. Lisa Neufeld says:

    My car only heats up when it is idaling or when is at a stop. The temp goes back to normal when driving especially on the freeway. I’ve replaced radiator, water pump, timing belt, cooling sensor, and thermostat. I’ve actually replaced the thermostat several times. Once repairs had been done car would be normal temp for a bit then it starts to heat up bout 2 weeks later. There are no leaks and head gaskets are good. Any suggestions?

    • Lisa Neufeld says:

      Also all fluids are good with no loss.

    • Michelle says:

      This is exactly happening to me. Did you ever find out what it was?

      • Curt says:

        I am having this problem with my jeep grand cherokee as well. I am tired of this. I’ve been dealing with this for too long. I put money into changing all of those things and it still does this. Why can’t anyone fix this!!?

        • Jrhea says:

          My Jeep has the same problem I have had it in the shop 3 times now and they can’t figure it out. I love my jeep but I am ready to trade it in. I don’t understand why no one can findthe solution either.

    • Brandon Williams says:

      My car does this too. I drive a 2012 Ford Fiesta SE 1.6 L 4 cylinder. I’m starting off with the small non expensive items before, fuse and relay. I changed the fuse just this past day and noticed that when I turned on my A/C, that smoke would come from the radiator fan, so I’m hoping that I need to replace just a relay and not the fan. I’m also going to see if maybe it’s the fans wiring, but I have to wait for my brother-in-law to see if he has a voltmeter. I’m hoping to get this problem fixed as I live in southwest Texas and the heat without an A/C and with the car getting very warm are not mixing well.

  11. ajith says:

    my car is over heating while i am corsa el 43 ( 5 e )

  12. i have a 02 300m 3.5 eng g, i had the radiator replaced for a leak, after that it would overheat below 2700 rpm in any gear,above it cooled fine, had the w/p replaced & all timeing parts while they were there, still same promblem, installed another radiator,flushed cooling system, put in correct fluid twice, the initial rad had wrong fluid put in, changed thermostat, hollds 15 psi for 24hrs then released, original spark plugs good,still the same problem, any ideas, thanks pete

  13. Dickson says:

    Where is the thermostat found on hino ho7d

  14. suzette van tonder says:

    We have a 2003 opel zafira 1.8. The car keeps on overheating if driving on open road. The waterpump,cambelt,thermostat, radiator are all replaced and it still overheats. What can this be.

  15. […] resulting in an imminent fire. To prevent the engine heat up, experts advise all drivers to closely inspect the engine temperature, especially in hot summers. If you notice temperature rising too high, stop your car by the road […]

  16. fouad says:

    Dear ,
    i have a nissan pathfinder 2004 running 123000 km .once i drained the coolant and i refilled it the engine started over heated , after that i change the thermostat and i flushed the radiator .but still the engine became over heated , special when you gave more torque the temperature will be increase .
    can you help me to find the failure .


    • Dave says:

      You may have created an air pocket in engine and engine needs to be burped. This can be done by elevating from of car removing radiator cap and letting engine run until thermostat opens. Then refill radiator to make up for displaced air. I’ve had this happen before too

    • mahmoud says:

      Hi Did you solve this problem dear and how please i have the same

  17. Adrian says:

    Jeep wrangler 2000, will only overheat after highway drive around 25 minutes. Local drives the needle sits just above halfway. I replaced the thermostat.

  18. fredy says:

    So my cluster is marking its over heating but my engine is cold and am on the road the engine is not overheating at all is it my sensor?

  19. Junaid says:

    Willim . Cheek the water jacket hols he is open ?

  20. Junaid says:

    Willim . Cheek the water jacket hols their is open ?

  21. jesse says:

    yes i have a question my car overheated and i took it to a mechanic he said the the muffler is licking water and there is some white smoke coming out he said that the best thing is to change the motor what do you think i should do another person told me i could fix just half of the motor that will be doing the job but i do not know to much of cars and i do need that help

    • Boris says:

      I have a problem with diesel engine. After rebuild (new piston rings bearings and gaskets) it wont start. Timing belt ok. It is posible to start it by pushing the car and then engine has no power, can’t work on idlle and over heating very fast (I remove thermostat). Also I check bearings and it looks good. Engine is not hard to move with key on crankshaft. All liquids ok. Help please.

  22. Wendy says:

    I have 2002 chrysler sebring. Temperature gauge say normal but the car is overheating.

  23. Aoniba says:

    my car is overheat while driving and the speed is very low while pushing to drive. Could you help me with it??

  24. Aoniba says:

    the model is Nissan, Liberty

    I really need to know the spare parts and also to be fixed if you know.

  25. Cate ndish says:

    My car is overheating,did ovahaul but stil overheating with alot of smoke.please help urgently.

  26. Petra says:

    I have a 04 Ford Focus. In the last few weeks I noticed my temp gauge started moving up. It hasn’t reached red yet but it stops right before. At first it was only happening if I drive in hot temps/long distances and especially and stopped at lights. But now it’s been happening in cool temps without much driving. Coolant level good. I have been told I have a coolant leak but it hasn’t been a problem till now.


  27. My boyfriend just put in a new thermostat, new top radiator hose and a new radiator my car is still over heating can somebody please give me a helping hand here and let me know what’s going on with my car I do not know nothing about cars

  28. Tommy Rancher, sr says:

    I have a 2003 Durango, it keeps shutting down when the guage reach the half way point. I change the radiator, starter, alternator, and thermostat. But it still shut down when it reach the half way point. Please help, I have spent over $500 in one week on this truck..

  29. benjamin says:

    i have replaced gasket, radiator cap, water pump, and the sensor, and crankshaft sensor, cleaned my radiator but the vehicle is still overheating what might be now the problem please assist

  30. Dana Mari says:

    My son has a 2002 Honda Civic with 70,000 miles. It broke down, it was overheating. We just got the radiator and thermostat changed. The temperature gauge is still going up but car doesn’t show signs of overheating. Running smooth. Any idea what else might be happening?

  31. Rudy says:

    Hi my gmc envoy keeps turning off and the computer reading said faulty thermostat. Is it possible for that to be the cause even if the vehicle is not overheating?

  32. junior says:

    last month i bought audi tt 2003 93000kms,it’s temperture gauge shows 90 whenever we starts the engine and after drive 5min, it goes 130 really fast ,but i checked radiator( water and coolent mix was just normal hot) ,we changed temperture sensor aswell but still same problem.please help

  33. khaled says:

    my problem started one month ago when i bought gmc acadia slt 2011. there was a problem in the differential and i solved by replacing it . i drove the car for five days and everything was fine. then the engine started overheating two lines after the middle. which means the first quarter. i took my car to the mechanic and he changed the thermostat , the fans and the sensor and some fuses , i took the car and after two days it started overheating and the ac started turning off. i took to another technician and he did know what to do . in liberty which is the car company said it is fine but actually it was not fine . one mechanic told me to check the condenser and i did and it was clogged and leaking and I changed it. then the car started reducing the engine power and makes white smoke with a fuel smell . i took to the company again and they changed the injectors and high pressure pump and some other stuff . i took the car and the ac was not working fine. and the car overheated again. i took to another mechanic and he changed the ac compressor and valves the front and rear and condenser again.I took the car home . it did not over heat. the second day it overheated . the car overheats in traffic and if turn the ac off it becomes fine . the engine is good and the power is fine . all the mechanics said there is no faults in the engine. I am still suffering , can you help.

  34. Krystle says:

    I have a 04 Jeep Grand Cherokee Largo. I just replaced the cooling fan and it still overheats. What else could it be.

    • shawn michael says:

      check for a fuse, i replaced my fan and let it idle so that i could see if it would over heat, it took 30 minutes? and it overheated, this told me there was another problem, i checked for the fuse and sure enough it was a fuse that was blown. now you would say, should have checked the fuse first, yes, but there was a reason why the fuse blew, and so by changing the radiator fan helped because it never occurred again.
      so there are a few things to watch for
      radiator, (leak) (low level)
      rad fan
      fuse relay
      also, when in trouble and see the temp gauge hitting hot, turn off ac turn on heat and hit the fan to blow as much of that heat out of the engine into the car, open the windows. also, if you can, get your speed up and put into neutral and turn engine off and coast as far as you can before turning on engine again, and do it again, this will help cool the engine down so that you can get back, depending on how far.
      a rad flush should be performed at times also. as per maintenance instructions.

  35. jack says:

    i have a 2008 pontiac g6 gt 3.5L. i have checked all major problems for why my car is overheating. I’ve checked thremostat, water pump, there are no leaks on the hoses. coolint is full. kinda stuck on this one. any ideas on what my problem could be? i would be very grateful if someone could help me with my problem.

    • Chris says:

      Hey man I am having the same problem on my 08 g6. I’ve replace the thermostat first than the radiator started leaking so I replace it. Bleed the system and it’s still running hot. I’ve checked for all major problems and I also change the coolest temp sensor. So I was wonder what was your solution to your problem cause it hits the nail on the head with what you posted. Thanks. Chris

  36. Aurora says:

    I have a 2005 Kia Sedona. Our van overheats after a few miles. It has no heat when the car is first turned on. After about 10 mins the heat will kick on and the gauge will go back to normal range… then it will start to overheat again and then heat will start back up and it will go back to normal range. Can you please help us figure out what could be the problem. We do have to add coolant to it also, but there doesn’t appear to be any leaks (or at least nothing we can see under the van). It doesn’t hiss when it overheats and no smoke from the engine.

  37. Howard says:

    how long does it take a large V8 engine to cool down after being shut off and parked in a one car garage in Florida

  38. micheal says:

    my engine is over heating..i replaced thermostat radiator cap fluids and passes the midway mark of the temperature gauge bout 3/4 of the way then cools back down a little then sits there havent had it hit the red mark..but i need to fix so i can drive with no worries..any help to solve this problem?

  39. imran says:

    MY car was being driven by friend in a hilly area, he reported that at end it got over heated and there was some gas coming out of radiator bottle, after it cooled down approx 1.6 liter water was required to fill radiator and extra bottle.
    After that car is normal i did nt experienced any change except some smell from bonnet, should i go for any inspection/maintinance?

  40. Yana says:

    Hi i have a Hino 500 1626 truck that overheats and cuts off while your driving what can be the cause of it, but when you try to start it – it starts with no problem.

  41. Tabitha Patterson says:

    My car gets hot when u first drive it and then if u pull over and open the radiator cap it goes back down …. There is no water in my oil ppl keep telling me it might be a cracked head gasket but I’m wondering if I should replace the radiator ? Help me please

  42. Mekia says:

    My 08 acadia, gives the Engine hot’ Message when I turn heater on. Radiator and ovreflow jug is empty. Had similar issue when I started using heater last year. Took to mechanic then and he advised it could be a water pump or thermostat..but then issue just stopped. Refilled antifreeze and left heater off holding steady. Now being told it’s the head gasket, please help

  43. Mike woodworth says:

    I have a 1990 Subaru Legacy L. It’s been over heating.
    I have replaced the radiator, water pump, thermostat, radiator cap, re timed the vehicle. Replaced all cooling system hosea. Flushed heater core. It is still over heating…but when it does I have no warm air coming through heater.
    How can I fix this

  44. Gift says:


    – there are two fans: radiator and A/C
    – when A/C off, radiator fan does not turn on automatically
    – when A/C is turned on, both fans turn on and off at the same time automatically
    – engine temperature gauge shows i presume normal as it at half the mark of the temperature guage

    Harrier 2003 model

    • Valerie Lau says:

      Hello, did you manage to find out what was wrong? I am having the same problem with my fans and had just done top overhaul & now very worried if problem wasn’t solved it would happen again. Already broke fixing this Honda crv ??

  45. Scherita Hill says:

    Car ran hot replaced radiator, thermostat, the gauge is still going into the red HELP.
    Acura 2000 TL 3.2

  46. Have replaced water pump thermostat it runs hit when going over 69

  47. Ive changed my water pump and thermostat and cool ing sensor and cluth fan all belts om my 2003 yukon with 4.8 and still gets hot when i run my air ..but dropes back down once i drive it also get hot when i pull my boat ..i do have dexcool in it what else could be causeing this

  48. Jami says:

    We turn on the truck. Drive it for a bit. It starts heating up. But too much. It goes a little over 210 and then opens up, releasing hot air. The temperature goes down. If we idle too long, the temperature goes up too much, kicking the hot air off. Any thoughts?

  49. mahmood says:

    hi i have nissan sunny 2016 gulf specification. my car getting overheat problem . the problem is this is heat gage is going on half50 % than fan start run than gage coming on normal position 25 %. before it was not like this. gage always stop on 25 % even ac or or off. i changed the gage n thrmostate but still facing this problem . as per mechanis this is normal .no need to do anthing. pls advise.rewaak@

  50. davion Williams says:

    I have a 2002 pontiac grand prix. I recently changed out my thermostat and changed my radiator cap and my car is still running hot. What is causing this.

  51. Chris says:

    While driving I noticed the temp gauge go from half way to three quarters so I turned on my heater and it dropped down why is this what is the issue. Thermostat or radiator
    Thank you

  52. Gregory Morales Sr says:

    i have a 1992 honda accord….i replaced the timing belt, water pump, thermostat, coolant temperature sensor, coolant fan switch….no coolant loss and right now the fans do kick on, but always at the three quarter mark temperature wise….i dont know what else it could possibly be….

  53. anna says:

    I have a 2002 sunfire was wondering if I should even fix it, pipe in on the ground in front, it overheats been wrecked book value is from 200 to 450 it has been sitting for about a year and two fat tires

  54. JOHN says:

    HAVE TO PUT WATER IN Radiator EVERYDAY, … when fan motor comes on it starts over heating and when it goes off it will drop back to normal….. I have check my oil and no Milkey in my oil….. what could be the problem , don’t think its the head gasket ,also there no leaks anywhere…… need help…..

  55. B Marsh says:

    I’ve replaced water pump, radiator, all hoses, removed thermostat. drove ok for a week. now temperature gauge shows overheatin. but when I look at motor the radiator is cool.Fans are working, still has oil although I’ve had a slow oil leak for over a year. What could it be?

  56. Mike Hutchins says:

    Changed water pump in 2006 Chrysler 300 C and took for test drive. It was running hot before I even got a mile up road. Thermostat was changed about yr ago. HELP

  57. KEN says:

    Ford Edge 08, overheated. Inspected engine, no leaks, boiling coolant in reservoir. Let Cool down and restarted drove 30 miles without an issue. When I got home checked engine while running and the fan was working. Is it possible for a thermostat to stick closed and then open and operate normally

  58. Angel says:

    i have a Nissan pathfinder 2008, I have changed the thermostat, I have installed anew radiator, new water pump, and new fan clutch, and still overheating?

  59. Jameel says:

    My Car is overheating while driving at above 100Km/h with AC switched on, without AC its working fine.. i changed Radiator, Fan and Thermostat… please help

  60. lnweaver says:

    That’s good to know that the thermostat or a lack of coolant will cause overheating. It’s good that you can limit the potential causes to a few guesses. If you’re not good with cars, that may just be an issue for a mechanic to deal with, though.

  61. I have a 98 Honda Civic LX a month ago it was overheating found that my my radiator was cracked so I put a new one on and a new thermostat and cap. The last two days it has been overheating issue again between half way and hot. So I burped it yesterday and it Was ok for 80 miles then started again then cools down when I turn my heat on high. It’s not leaking not smoking fluids are fine hoses to and water pump is only 4 years old.. I need help??
    Rebecca Ohio

  62. My Chevy Sub. is loosing coolant through the heater overflow. I can drive it about 60 miles before it starts to overheat, I add water to coolant container and it cools down and so on. The water is coming out of the short tube from the firewall. any idea’s ?

  63. anza says:

    my engine in heating up when i start my ac in long journey but my radiator water level remains same and heat meter also don,t rises

  64. Toby says:

    Question: How come my engine overheated (and eventually fried) when the temperature gauge read normal. We had no warning, check engine light came on, normal temp, no steam, no smoke, nothing. Engine died. Opened the hood, no radiator cap was present. Two issues: the radiator cap missing (this was shortly after an oil change and check of fluids) and why did the temperature gauge read normal all this time of excessive overheating and finally fried the engine. If the thermostat was stuck in closed position, thermostat would show overheating. Nothing, it was normal. Garage said the radiator cap “blew off” when it got excessively hot with temps on the coolant system at 46psi. I have a hard time believing that since radiator caps are rated for 12-14psi. Other hoses would have blown before a radiator cap is blown off. My dealer said caps never, ever get blown off. I am baffled. No radiator cap present, no coolant in system, temperature gauge reading normal. (Check engine light did come on late after it was too late. (Garage indicated 8 mins and it was toast.)

  65. April says:

    Hi I was driving and out of no where my car gets hot . the dash said engine coolant is hot then didn’t want to excellarate. Am I low on coolant or what? I opened coolant cap and its empty what do I do.

  66. Megan says:

    I have replaced thermostat and radiator. Haven’t blown a head gasket but the car is still overheating. It is an 04 Nissan Maxima


    I have a problem with my opel astra G turbo coupe it’s overheating and high pressure

  68. When i turn my ac on it doesnt leak raditor fluid. But if i drive without the ac after it get hot it start to leak

  69. Jean says:

    I have an Audi tt 2003. It is overheating. I have changed all the following: Thermostat, Radiator, Coolant, Temperature Sensor, Water Pump, Timing Belt, both fans. Still, it is overheating. I know I don’t have a head gasket problem because there is no smoke coming out of the muffler pipe. Pleas help, this car is driving crazy. Thanks!

  70. DStein says:

    What would be the price ranges for fixing a thermostat all the way to a blown head gasket? Just a ballpark would be helpful as I did everything that Google said as far as put coolant in and the needle remained normal and then my car burn up and would not restart. So now I’m looking at repairs and would like to make sure I don’t get ripped off as a lone female out here in the world.

  71. Anthony says:

    I have a 95 cadillac seville and my problem is it keeps overheating and leaking antifreeze only when the a/c is on. It doesn’t leak or overheat as long as the a/c is off. Matter of fact it runs perfect when its off. Can anyone help me?

  72. Daughters car overheated so my husband was looking at it and changed gasket. Its not overheating but now won’t go over 24 mph. Any idea on cause ?

  73. amber says:

    I have a 2009 Pontiac G6 it was overheating but as long as I kept water or coolant in it it wouldn’t overheat except for now it’s overheating as soon as I get down the street what could it be

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