How do you replace a thermostat on a 2000 Pontiac Grand Prix 3.1 liter?

Answer 1

GM 3.1 SFI Thermostat replace

Tools required:

1. 13 MM, 12 point, box end wrench for lower thermostat housing bolt

2. 3/8 ratchet

3. 3/8 drive 13 MM wobble socket or 13 MM short socket with universal joint for upper thermostat housing bolt.

4. 3/8 drive 6" extension

5. 9/32" socket or end wrench for bleeder screws

6. Channel Lock to release hose clamps. Also a normal pliers for the small clamps if using Method 1.

7. Siphon tube

8. Container to capture antifreeze

9. Latex gloves

Procedures:

1. Let the car cool down.

2. Siphon about a gallon of antifreeze from the radiator.

3. Follow the top radiator hose on the driver's side to the engine and remove the hose from the thermostat housing. The thermostat is under the thermostat housing. There is no gasket because the thermostat has a rubber ring built onto it.

4. Remove the rigid PCV intake hose from rubber air inlet duct

5. Loosen the air inlet duct clamps on the air cleaner and throttle body, and move the duct aside. This is a perfect time to check the air cleaner element and clean the housing of debris.

6. There are couple of methods you can use to remove the thermostat housing.

Method 1. Removing the throttle body. You will need a new throttle body gasket but it makes getting at the lower thermostat housing bolt easier. You will also need to remove the little coolant hoses that feed the throttle body. It does give you the opportunity to clean the throttle body with carburetor cleaner if you wish. This method requires no more explanation since the thermostat housing lower bolt will be fairly accessible.

Method 2. Without removing the throttle body. You will not need any parts other than the thermostat, but you have very little room to move your wrench on the bottom thermostat housing bolt, which makes it slow going. It generally requires you to remove one coolant line from the heater core where it connects to the steel tube by the throttle body in order to get the lower bolt back in, depending on the length of your fingers.

a. Optionally, remove the heater hose that runs to the metal tube near the throttle body. You can get the lower bolt out without this step. The problem I have without this step is getting the lower bolt back in.

b. Remove the lower bolt first. You will need to maneuver your hands both under the exhaust manifold on the front side and from behind the exhaust manifold on the back side to move the 13 MM box end wrench 30 degrees at a time. This is why you need a 12 point box end. You could try the ratcheting box end wrench, but when it starts to get loose, it's tough to put enough friction on it for the ratchet to work. You will hear people talk about how the hosing is slotted so you don't need to remove it all the way. That is false. That only works on old 3.1 non-SFI engines, some of which have a long stud and nut. You cannot remove the thermostat housing without removing the bolt because the thermostat extends into the thermostat housing for longer than the bolt.

7. Remove the upper bolt with the 13 MM socket, universal joint, extension, and ratchet.

8. Clean the face of the thermostat housing and recess there the thermostat fits into the inlet manifold in the thermostat rubber seal contact area.

9. Insert the new thermostat into the inlet manifold, spring end first. Make sure it is in all the way so the rubber ring does not get pinched when you tighten the thermostat housing down on top of it.

10. Replace the thermostat housing.

11. Using the 9/32" wrench or socket, open the bleeders on the thermostat housing and water pump. The water pump is located on the passenger side on the front of the engine on the steel water manifold.

12. Pour as much antifreeze as will fit into the radiator.

13. Start the engine to bring it up to temperature, and turn on the heater.

14. While it's running, watch the bleeders. When antifreeze starts to come out of a bleeder, close that bleeder.

15. When the thermostat opens, the level in the radiator will drop and you will be able to pour in most of the remainder of the antifreeze. Replace the cap. Pour the little remaining into the reservoir.