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How to Change the Thermostat in a Pontiac Grand Prix

by Contributor

Pontiac introduced the Grand Prix as a "personal luxury car," which means a big coupe with a big engine, a fancy interior and an exterior that sometimes bordered on the flamboyant. Grand Prix maintains its popularity over the years as its niche is a sensible family sedan with various engine options.

Remove the Thermostat

Drain about half the engine coolant into a sealable container. Disconnect the negative battery cable.

Take the hose clamps from the water inlet housing with a pair of hose clamp pliers. Remove both the radiator hose and the heater hose from the water inlet housing.

Disconnect the clamp on the surge tank inlet hose. Take the hose from the water inlet housing.

Loosen the bolts that secure the water inlet housing then remove them. Lift out the water inlet/thermostat assembly.

Install the Thermostat

Clean the sealing surfaces to remove all traces of gasket material and dirt. Position the new inlet-thermostat assembly on the engine.

Apply RTV Sealer GM#1052366 or a similar product to the bolts before installing them. Tighten the bolts to 80 inch pounds.

Connect the hoses to the surge tank, the heater and the radiator to the inlet housing. Fill the cooling system with the proper type and mix of coolant.

Reattach the negative battery cable. Start the engine and allow it to run until the thermostat opens.

Allow the engine to cool. Test the coolant level and add coolant as needed.


  • The hoses slide onto fittings or connectors that grip the individual hose and hold it in place with a clamp.
  • No special tools are required to remove or reconnect hoses. Label the hose and its connectors before separating.


  • Keep in mind that dogs and cats are attracted to and will drink coolant left in open containers or puddled on the floor and ingestion is often fatal. Reuse the coolant unless it's contaminated or old.

Items you will need

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