How to Replace a Thermostat on Pontiac Cars

by Contributing Writer; Updated June 12, 2017

The Pontiac car is considered to be a sport sedan that is not only capable of taking the kids to football practice but can get them there fast. High-performance vehicles like the Pontiac car can be prone to engine failure if attention is not paid to the systems that keep the engine performing properly. The oil needs to be changed regularly and the coolant system should be inspected. If you've noticed the engine running hotter than usual, inspect the thermostat sooner rather then later.

Under The Hood:

 How to Replace a Thermostat on a 2001 Pontiac Sunfire

Pop the hood release to access the thermostat housing. Locate the top hose on the radiator. Trace it to the engine.

Unbolt the hose clamp holding the hose to the thermostat housing with a flat screwdriver. Pull the hose off the housing by hand.

Unbolt the two bolts holding the thermostat housing together with a socket wrench. Pull the cover off the thermostat housing.

Pull the thermostat out of the assembly by hand. Discard the old thermostat.

Scrape the black gasket material around both surfaces with a razor scraper. Ensure both surfaces are clean.

Deposit the new thermostat into the housing with the spring end down. The thermostat will rest inside the housing.

Position the new gasket around the bottom surface of the housing. Ensure the bolt holes on the gasket match up with the bolt holes on the surface.

Bolt the surfaces together with a socket wrench. Ensure the surfaces are bolted tight to prevent leaking of coolant.

Slide the hose over the inlet pipe. Slide the hose clamp over the hose and the pipe. Tighten the hose clamp with a flat screwdriver.

Twist the radiator cap off to fill the radiator with coolant. Pour in pre-mixed coolant into the radiator until it is full.

Start the car and allow it to warm up. Once the car is warm, the level of coolant will drop. Fill the radiator with additional coolant until it can not hold any more coolant.

Tighten the radiator cap back onto the radiator. Close the hood and turn the car off.

Items you will need

  • Flat screwdriver

  • Socket wrench

  • Socket set

  • Razor scraper

  • Pre-mixed antifreeze

 How to Replace the Thermostat on the 3.1 Grand Prix

Pull the Grand Prix with the 3.1-liter engine into a safe and level work area. Set the emergency brake and open the hood. Shut the motor off and wait two to three hours for the engine to cool down completely.

Slowly unscrew the radiator cap and set it to the side. Make sure that the cap is not hot and does not have pressure on it. Slide the drip pan underneath the radiator drain plug on the bottom of the radiator. Loosen the drain plug with the pliers and allow a couple of gallons of coolant to drain into the drain pan. Tighten the drain plug back down tight.

Locate the top radiator hose that connects to the top radiator port and the intake manifold. The other end of the radiator hose connects to the thermostat housing on top of the intake manifold. Unscrew the hose clamp from the end of the hose that is attached to the thermostat housing port with the pliers. Pull the clamp back onto the hose. Twist and pull the hose off the thermostat housing port.

Unscrew the two thermostat housing mounting bolts with a ratchet and a socket. Pull the housing off and set it to the side. Pull the thermostat out of the intake manifold and discard it into the drain pan. Scrape away any of the old gasket from the base of the intake manifold and the bottom of the thermostat housing. Wipe away the excess gasket, dirt and debris from both places with a clean rag.

Spread a thin line of the red high-temperature silicone around the bottom of the thermostat housing. Push the gasket onto the bottom of the housing so that the silicone will hold the gasket in place and act as a extra sealer. Make sure that the bolt holes are matched up on the gasket and the thermostat housing.

Set the thermostat housing back over the intake manifold and match the bolt holes up. Screw the two mounting bolts through the thermostat housing and tighten with the ratchet and socket.

Push the top radiator hose back over the thermostat housing port and line the hose clamp over the radiator hose and the port. Tighten the clamp with the screwdriver until the hose is securely tightened to the thermostat housing port.

Add the antifreeze to the radiator until it is full. Leave the cap off the radiator. Crank the motor and let the engine heat up until the thermostat opens. The thermostat generally opens around 180 degrees. When the thermostat opens, the antifreeze level will drop inside of the radiator. Keep adding more antifreeze to the radiator until the antifreeze stabilizes at the top of the radiator cap. Screw the cap on tight and turn the engine off.

Items you will need

  • Drain pan

  • Pliers

  • Flat-head screwdriver

  • 1/2-inch drive ratchet

  • 1/2-inch drive socket set (metric)

  • Flat metal scraper

  • Clean rags

  • Red high-temperature silicone

  • New thermostat with gasket

  • Antifreeze

 How to Replace the Thermostat on a '95 Grand Am

Disconnect the negative battery cable from the Grand Am's battery. While this is not strictly necessary, it is good practice when doing any kind of auto work to make sure there is no active current running through the vehicle.

Raise the Grand Am off the ground with a hydraulic jack and then lower it onto jack stands.

Position the bucket under one of the Grand Am's radiator hoses. You will be draining the coolant out of the radiator and into this bucket so as to prevent spills while working on the thermostat.

Loosen the hose clamp on one of the lower hoses with your flat-bladed screwdriver, then pull the hose away from the Grand Am's radiator to start the coolant draining into the bucket. Once it has drained, seal the bucket and place it off to the side.

Locate the Grand Am's thermostat housing. This can be found between the engine and the firewall on the passenger side of the vehicle. If you are having difficulty locating it, follow the largest hose on the upper portion of the radiator until you find the piece it connects to. This is the thermostat housing.

Loosen the two retaining bolts with your ratchet and socket set, then pull the thermostat housing up and away from the Grand Am's engine to expose the thermostat.

Grab the handle of the thermostat and pull straight up to remove it from its setting. Once the thermostat has been removed from the engine, you may discard it.

Use your razor blade--or a scraper tool, if you have one--to clean the remnants of the old thermostat O-ring or gasket from the bottom of the thermostat housing and from the thermostat setting. It is important to get these points as clean as possible to ensure a good seal and to prevent coolant leaks.

Apply a layer of gasket sealer to the bottom of the thermostat housing and press the thermostat gasket against it, making sure it sticks firmly.

Install the new thermostat into the thermostat setting, then replace the thermostat housing and secure it down with the two retaining bolts.

Replace any hoses you may have loosened or disconnected during this procedure, then lower the car back to the ground, take off the radiator cap, and start the Grand Am. Let the vehicle run until the large upper radiator hose is hot to the touch, then turn the car off and pour the coolant back into the radiator.

Items you will need

  • Jack

  • Jack stands

  • Flat-bladed screwdriver

  • Clean sealable bucket

  • Ratchet and socket set

  • Razor blade

  • Gasket sealant

  • Replacement thermostat

  • Thermostat gasket

 How to Change the Thermostat in a Pontiac Grand Prix

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.

Items you will need

  • Mechanic's toolset, including a full socket set, wrenches and screwdrivers

  • Replacement thermostat, new or rebuilt

  • New gasket for thermostat

 How to Change the Thermostat in a Pontiac Grand Am

Disconnect the battery ground cable. Drain the engine coolant in to a suitable container.

Remove the bolts that hold the water pump feed pipe to the thermostat housing. Take out the water pump feed pipe. Lift out the thermostat.

Clean the thermostat sealing surfaces completely. Remove any old gasket material and dirt.

Install the new thermostat. Connect the water pump feed pipe to the thermostat.

Set the bolt in place that holds the water pump feed pipe on the thermostat housing. Torque the pipe bolt to 89 inch pounds.

Refill the cooling system, recycling the coolant. Add more coolant as needed. Reconnect the negative battery cable.

Start the engine and allow it to run until the thermostat opens. Turn off the engine and let it cool. Recheck the coolant level and add coolant as needed.

Items you will need

  • Mechanic's toolset, including a full socket set, wrenches and screwdrivers

  • Replacement thermostat, new or rebuilt

  • New gasket for thermostat

 How to Change the Thermostat in a 2002 Grand Prix

Remove the radiator filler cap on the Grand Prix and set it off to the side. The engine should be cool to prevent the cooling system from spraying vapor out of the radiator filler.

Remove the radiator hose from the thermostat intake housing by removing the band clamp that holds the hose to the housing. This is done with a nut driver or a screwdriver. Slide the band clamp further onto the radiator hose to prevent losing it and pull the hose off of the housing. Push the radiator hose off of the side. It's possible that fluid will leak out of the hose. To prevent this, keep the open end of the hose facing upward.

Remove the two bolts that hold the thermostat intake housing onto the Grand Prix's intake manifold with an 8-mm wrench or socket. The bolts should be retained as they will be used again when installing the new thermostat.

Pull the old thermostat out of the intake manifold and discard it. Pull the old thermostat housing gasket off of the intake manifold and discard it. Nether item will be used again.

Place the new thermostat into the intake manifold. The thermostat must be put into the engine with the correct end up. The thermostat will be stamped "top" on one end. This is the end that should stick out of the engine.

Place a small bead of PVC gasket maker on the machined mating surface of the intake manifold. Allow the PVC to "skin over" or cure for 15 minutes. Place the gasket on top of the PVC gasket maker. Place a small bead of PVC gasket maker on the bottom lip of the thermostat intake housing and allow it to cure for 15 minutes. Place the thermostat intake housing onto the intake manifold and tighten it down with the original housing bolts. A small amount of gasket maker will squeeze out of the seam. This is normal and will aid in the sealing process.

Reconnect the radiator hose by sliding it onto the thermostat intake housing and tightening down the band clamp. Place the radiator filler cap back onto the radiator.

Items you will need

  • Grand Prix thermostat

  • Grand Prix thermostat gasket

  • 8-mm wrench

  • PVC gasket maker

  • Screwdriver

About the Author

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.