Thermostat Housing

It is often plastic on modern engines. Sensors may be mounted in it. It is sealed with a gasket or O-ring. Some housings include the thermostat as one replaceable unit, often with an integrated coolant temperature sensor. Cracks in plastic housings often begin as a slight dampness or white crust before a visible leak. Tighten bolts to the specified torque to avoid cracking new housings.

Coolant flows through the housing.

Plastic housings can crack and leak. Replace seals with the thermostat.