Question about 1999 Pontiac Grand Prix

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How do you change the thermostat and the radiator hose on a 1999 pontiac grand prix

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  • Anonymous May 27, 2010

    The same as any other vehicle. Tell me you have never done one before, not that you can't find the thermostat


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  • Pontiac Master
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Thermostat - REMOVAL & INSTALLATIONCAUTION Never open the radiator cap or the cooling system when the engine is hot. The system is under pressure and will release scalding hot coolant and steam which can cause severe burns and other bodily harm. After the engine has cooled, drain the coolant into a suitable container. Coolant should be reused unless it is contaminated or several years old.
3.1L, 3.4L (VIN X) and 3.8L Engines

  1. Disconnect the negative battery cable.
  2. Partially drain the cooling system into a suitable container, to a level below the thermostat.
  3. It is usually possible to leave the radiator hose attached and simply remove the thermostat housing (also called a water outlet) and flex the radiator hose enough to service the thermostat. It is good practice, however, to remove the radiator hose so the thermostat housing can be given a thorough cleaning. Debris on the thermostat housing sealing surface can cause leaks.
  4. Some applications may have electrical connections to sensors which mount in the thermostat housing. Use care when detaching these connectors.
  5. Unfasten the thermostat housing bolts and remove the housing.
  6. Remove the thermostat by simply pulling out. Discard the gasket.
To install:
  1. Clean all parts well. Make sure the sealing surfaces on both the thermostat housing gasket flange and the intake manifold are clean and free of corrosion damage. It is good practice to run a thread cutting tap or a clean bolt into the threaded holes in the manifold to clean out old sealer and dirt. The threads should be clean so the thermostat cover clamps the gasket evenly at assembly.
  2. Position the thermostat in the intake manifold. Make sure it is seated.
  3. Position a new gasket over the thermostat. If no gasket is used, apply a 0.125 in. (3mm) bead of RTV sealer to the thermostat housing and install the housing. Lightly lubricate the bolts with clean engine oil. Torque to 18-20 ft. lbs. (23-27 Nm).
  4. If removed, attach the radiator hose to the thermostat housing.
  5. Refill the engine with the proper mix of DEX-COOL® and water. Connect the negative battery cable, start the engine and check for leaks.

Hope helps (remember rated and comment this). Good luck.

Posted on May 28, 2010

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  1. Disconnect the negative battery cable.
  2. Lower the coolant level a bit.
  3. Follow the top radiator hose to the thermostat housing.
  4. I would just leave the hose on for this thermostat and go right to removing the two mounting bolts.
  5. Pull the housing up and clean the gasket off bothe sides of the gasket real well. Becarefull not to gouge the aluminum.
  6. Install the thermostat with the little "tip" facing up.
  7. Now put the new gasket and a little sealer on it too.
  8. Reverse the previous steps to finish the installation.
  9. When you get the antifreeze full remember to burp the system with that little bleeder valve on top.
  • see diagram below for a visual.


  • Hope this helps.

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