The thermostat in the 4.3-liter GM engine is in the front, on the top center area. Install a new thermostat when the engine is running hot or overheating regularly. The thermostat can stick shut and not allow coolant to run through the block, causing the engine temperature to increase until it overheats. If that happens, the engine can be damaged internally, leading to blown head gaskets, cracked engine blocks and damaged heads.
Instructions
- 1
Place a drain pan under the radiator and open the drain petcock at the bottom of the radiator. Drain the radiator until the coolant level falls below the level of the upper radiator hose
2Follow the upper radiator hose down toward the engine until you locate the thermostat housing on top of the engine. Remove the hose clamp using a screw driver and pull the hose off the thermostat housing.
3Remove the two mounting bolts that hold the thermostat housing on the engine. Carefully remove the housing from the engine block by wiggling it. If needed, pry the housing loose with a flat screwdriver.
4Clean the sealing surfaces of the housing and block with a putty knife. Scrape off any pieces of gasket or other material that may cause the housing to not seal properly.
5Remove the old thermostat and discard it. Install the new thermostat into the hole in the engine block. Be sure to orient it properly or it will not work correctly.
6Place the new gasket on the block and set the thermostat housing in place. Insert the two mounting bolts into the housing and thread them into the block. Tighten the bolts using a socket and ratchet, working back and forth between the bolts so you pull the housing down evenly.
7Reinstall the upper radiator hose and clamp onto the thermostat housing. Tighten the clamp with a screwdriver. Do not over tighten the clamp or you may damage the hose.
8Refill the radiator with coolant and start the engine. Let the engine run, checking for any leaks and verify that the engine does not overheat. Replace the cap after the system is topped off.
