The thermostat is a small spring loaded valve that controls the flow of coolant between the radiator and engine. As the engine heats up, the thermostat opens and allows coolant to flow to the engine to reduce its temperature. A defective thermostat will either fail in the open or closed position. If the Bravada’s thermostat remains open over-cooling occurs which leads to no heat when the blower motors turned on. A closed thermostat will quickly raise the engines temperature and cause mechanical failure. You can change the thermostat on the 4.2-liter 2001 Bravada right at home. The repair should take you 40 minutes or less to do.
Raise and fully support the hood on the Bravada. Remove the radiator cap and place a coolant drain pan underneath the radiator.
Open the drain-cock on the radiator and completely drain all of the coolant from it. It should take 10 minutes to fully drain. After this time close the drain-cock securely.
Locate the thermostat housing on the side of the engine below the alternator. It’s not necessary to remove the hose from the thermostat housing. You can access the thermostat easily once the housing unbolted.
Slide your coolant drain pan directly beneath the thermostat housing. This way any coolant that comes out of the housing will go into the drain pan and not on the ground.
Remove the two bolts holding the heater core housing to the engine with a socket wrench. Pull the housing away from the engine and take out the thermostat.
Soak up any residual coolant from the thermostat’s mounting area on the engine with a shop rag. Then use another dry shop rag to go over the area once more including the flat mounting surface of the thermostat housing.
Install the new thermostat just as you removed the old thermostat. Your new thermostat should have a rubber seal already installed on it, if not you have the wrong replacement part.
Position the thermostat housing back into its original location and then return both of its bolts by hand to insure they thread correctly. Set your 1/4-inch drive torque wrench to 89 inch-lbs. and completely secure both bolts in place.
Refill the radiator with fresh coolant or with the coolant from the drain pan if it’s less than three years old. Return the radiator cap and then start the engine on the Bravada. Check for leaks every five minutes until the engine reaches normal operating condition. Take the truck for a test drive once you’ve determined there aren’t any leaks present.
