If the radiator is filled to the top with coolant and the engine is run without the radiator cap in place, the coolant will expand and spill over as the engine warms up.
- Drain some coolant into a clean container until the coolant level is below the thermostat housing.
- Remove the upper radiator hose connection from the thermostat housing.
- Loosen the housing bolts and remove the housing.
- Remove the gasket and scrape it carefully from the surface of the housing and the mounting surface on the engine. If the gasket remains on either of the surfaces, there will probably bea coolant leak after reassembly. Some engines use a rubber O-ring to seal a thermostat housing.
- Compare the size of the thermostat to the old one. They are of different sizes, types, and temperature ratings.
- The temperature rating is stamped on the sensing bulb on the bottom of the thermostat. The temperature bulb faces the block.
- When replacing a thermostat, be sure that the thermostat fits into the groove in the block or outlet housing. If the thermostat is installed upside down, the engine will overheat.
- Install the gasket.
- Reinstall the thermostat housing. Refill the system and run the engine or pressure test to check for leaks.
- When the engine has reached operating temperature make sure the thermostat opens.
- You should be able to see coolant circulating within the radiator.
- Another way of checking thermostat operation is to feel the top of the radiator hose or use a thermometer or multimeter with a temperature probe to confirm that the coolant is warming up.
- If the engine is overheating, but the top hose is still cool to the touch, the thermostat is stuck closed and must be replaced.
When replacing the thermostat, also replace the gasket that seals the thermostat in place and is positioned between the water outlet casting and the engine block.
Generally, these gaskets are made of a composition fiber material and are die-cut to match the thermostat opening and mounting bolt configuration of the water outlet. Thermostat gaskets generally come with or without an adhesive backing. The adhesive backing of gaskets holds the thermostat securely centered in the mounting flange, leaving your both hands free to align and bolt the thermostat securely in place.
- Remove the thermostat housing.
- Remove the gasket and scrape it carefully from the surface of the housing and the mounting surface on the engine. If any gasket remains on either of the surfaces, there will probably be a coolant leak after reassembly.
- Some engines use a rubber O-ring to seal a thermostat housing.
- Install the gasket.
Hopefully this is helpfully