Question about 1999 GMC Sierra

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Thermostat location on 1999 4.8 L v8 GMC Sierra

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  • admin63004 Dec 31, 2010

    Thanks for the help/advice. I'm going back to double check everything. Must have missed something somewhere, happens when you're in a hurry ;-)


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Hello Admin
The location of the thermostat is on the right front side of the engine about half way down on the end of the radiator hose.
It is visible on the diagram below just above the AC compressor. The bolts that retain it are also shown.
Thermostat location on 1999 4.8 - kiltylake_120.gif

Posted on Dec 30, 2010

  • 1 more comment 
  • FUBAR Dec 30, 2010

    Thank you for taking the time to rate the answer. It is appreciated....


  • admin63004 Dec 31, 2010

    Seem to be losing small amount of coolant, no visible leaks, no loss of power, no oil in water, no water in oil, no overheat. Heater does not get hot at all, barely warm. Installed new blend door actuator,no difference.

  • FUBAR Dec 31, 2010

    Hello Admin...The vehicle is over 10 years old so it is possible the heater core is partially blocked....It may need to be flushed or replaced....To check it, run to operating temperature and check the two hoses going into and out of the core. They should be very hot and close to the same temperature. If one is considerably cooler than the other the core is partially restricted..........As far as the coolant leak is concerned, have a pressure test done..A dry day is best. let it stay under pressure as long as possible and look for leaks. Small leaks are sometimes hard to locate, especially in todays crowded engine compartments.... If the pressure drops but not visibly it may be going inside the engine. Cracking the oil drain plug after the pressure test may reveal coolant if this is true. Coolant goes to the bottom as it is heavier than the oil.......There are a couple of tips for you. I hope you find the problem easily and inexpensively.......Take care.....Bernie.


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