How Do I Know If I Have A Bad Thermostat Or It Is Sticking

Posted in Cooling Perfomance | Asked on May 25, 2010

Its a 2002 chevy silverado and it gets hot idleing and my air conditioner changes speeds and you can hear it get more powerfull at times? Could that be a bad thermostat? It does not overheat all the time.

There are 9 Answers for "How Do I Know If I Have A Bad Thermostat Or It Is Sticking"

  1. pathfinder says:

    You answered your own question. The car/truck will overheat.

  2. mel says:

    It takes so much fuel to run this guzzler, it’s anyone’s guess.

    the AC turns on and off because the engine can’t turn the compressor at idle, and your more liable to overheat this guzzler running ac at idle.

  3. jyd9999 says:

    replace it

  4. marvin_g_33334 says:

    The Thermostat won’t affect the AC Fan ! A bad Fan Clutch will change the sound of the engine when it engages & disengages.IT sounds like the fan clutch is on the way out.DOES it keep spinning as soon as U turn the engine off.Does the Fan look like it is Barely spinning with the engine running-if so – time 4 a new fan clutch.

  5. bostonianinmo says:

    It could be a bad thermostat, or a failing water pump, or it could be completely normal. BTW, a sticking thermostat IS a bad one.

    The increased noise is due to the thermostatic fan clutch on that beast. When the engine is cool the fan free-wheels and makes less noise and draws less power. When the coolant gets hot, the clutch engages and speeds the fan up to increase airflow through the radiator. When the fan turns faster, it makes more noise.

    On very hot days it’s not unusual for the temp gauge to get near to the red zone when idling especially when the A/C is running. As long as you stay out of the red zone, you are NOT overheating and need not worry about it. If the needle does hit the red zone, switch off the A/C for a few minutes and rev the engine slightly to increase the airflow through the radiator and cool the engine down.

  6. Silverstang says:

    More and likely it is the cooling fan for the A/C not working. Need to get that fixed. Don’t really think its the thermostat. When you start your truck, turn on A/C to Max, ot high, and pop the hood, and see if the Electric fan is running. If not then there is your problem.

  7. bill k says:

    Thermostats get a lot of blame, but are rarely the problem. Before you change your thermostat flush your cooling system. A 2002 is past due and this is more than likely the problem.
    You can get a reverse flushing system at your local auto parts store. After you flush it re-fill with the RED coolant that is specifically for Late model Chevy’s. Do not use the green coolant it will not cool as well and can end-up clogging your system.

  8. BitburgerPilsMan says:

    I’ve found that usually if a thermostat is bad, it will get real hot the first thing in the morning one time, then cool down and run at normal temps after that.

    Or, the thermostat will stick open and the temp will go low.

  9. Blazs (Skoda 120GL) says:

    You can check if your thermostat is working (at least partly :) ).
    Start the engine and let it idling. Wait for the warm-up. Check the waterpipe that goes from the thermostat housing towards the radiator. as long as the egine is cold, the thermostat doesn’t open and doesn’t let any water into the radiator. When the engine starts to warm up, the thermostat opens, which you can feel by checking the radiator pipe with your hands. When the pipe is getting warmer, that means that the thermostat has opened and lets the hot water flooding into the radiator.

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