Engine Overheating Silverado 1500...Please Help!!!!

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by emy1, Jul 14, 2010.

  1. emy1

    emy1 New Member

    I have a 99 chevy silverado 1500 5.3L V8 with running hot problems, would be overheating if not for turning on the heat to bring the temp down. I have tried many solutions including the following;
    1. Flushed radiator twice
    2. Replaced thermostat twice
    3. Replaced fan clutch
    4. Replaced temperature sensor
    5. Replaced water pump
    6. Replaced radiator cap
    7. Replaced front two O2 sensors
    8. Checked all lines
    Now after alot of time and money and 3 different mechanics there isn't much left that anyone can think of. The mechanics are suggesting it could possibly be a crack head, but they are not confident b/c the truck runs perfectly fine as i can tell with the exception of the temperature. Usually within 10-15min the temp starts rising, but not consistent...other than it always gets hot.
    Been going on for over a year now...
    Engine not losing oil, or water...
    Still has good power...
    Still runs good...
    We did check the engine with a laser thermometer, and the engine was hot.
    Is there anything I can try...Please help and thank you in advance.
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Have you blead the system?? Also have you checked the lower radiator hose while the truck was running under throttle?? it could be colapsing not allowing water into the motor. Also a is the CEL on?? Since there could be an electrical problem letting the motor run lean and get hot. I did have this problem with my truck a bit older but similar fault.
  3. 04-silverado

    04-silverado Rockstar 100 Posts

    In addition to what murdog94 said...

    Ensure that the fan shroud is in place and that the radiator grill itself is free of debris/blockage.

    Years of bugs, road dirt & dust can build-up on the radiator fins/coils... using LOW-pressure air/water to flush it, is usually not sufficient. Application of AC-920 foaming cleaner, to the exterior surfaces of the radiator... followed by LOW-pressure air/water flush... should help to ensure efficient & proper "heat exchange" as air passes through the radiator.
  4. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    No chance it is pinging? You would have mentioned that I guess.
    Those motors did have a problem with building carbon above the top ring-and that caused the piston slap noise they are famous for. It didn't hurt the reliability, but the noise sure bugged owners.

    I was wondering if you could have a hot spot from carbon buildup that was causing pre-ignition which might cause it to run hot.Of course you would hear something and the knock sensor would be retarding the ignition-probably showing codes-check engine etc.

    Guess you have run it with the radiator cap off so you could see coolant pumping thru the radiator? And
    I would be tempted to remove the thermostat and run it just to make sure it isn't a thermostat problem.

    Just how hot does it get?

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