The thermostat in a General Motors LS1 engine is designed to prevent coolant from circulating through the engine until it reaches operating temperature, allowing the engine to warm up quickly. When the thermostat fails, the engine may overheat because coolant is never allowed begin circulating through the engine. The thermostat is located on the front of the engine to the right of the battery. An aluminum thermostat housing covers the thermostat and is secured to the engine block with two 10 mm bolts. Replacement thermostats are available from auto parts stores and Chevrolet dealerships.
Park the vehicle on a level surface and shift the transmission into park (automatic) or first gear (manual). Engage the emergency brake, turn off the engine and open the hood. Allow the vehicle to cool for 60 minutes.
Remove the radiator cap by pushing down on it and turning counterclockwise. This relieves the pressure from the cooling system.
Locate the aluminum thermostat housing on the front left side of the engine block, to the right of the vehicle's battery. It has a black coolant hose attached to it and is secured to the block with two 10 mm metric steel bolts.
Set a drain pan underneath the vehicle and remove the two thermostat housing bolts using a 3/8-inch ratchet and a 10 mm socket. Pull the thermostat housing away from the engine block and remove the thermostat. Replace the rubber o-ring on the thermostat housing.
Place a new thermostat in the engine block and reinstall the thermostat housing. Unscrew the cover from the coolant reservoir and add engine coolant until the level is even with the "FULL COLD" mark.
Replace the radiator cap, start the engine and check for leaks.
