view all articles
What Is The Purpose Of The Thermostat Housing?

In many internal combustion engines the thermostat housing acts as the coolant outlet, it is normally located on the engine block or cylinder head. Engine coolant is constantly flowing, it flows through ports located in the block and head; it travels through these two components, through the thermostat housing and into the radiator where the coolant is cooled. As the name implies, this engine component houses the thermostat which regulates the coolant flow.

Standalone vs. integrated:

All thermostats do the same job; they delay the circulation of engine coolant until such time as the engine warms up. On the engine side of the thermostat there is a little wax filled cylinder that doesn’t begin melting until the engine reaches the thermostat design temperature which is about 180 degrees F. There is a small rod connected to a valve that is closed when the engine is cold, when the wax melts it expands and in doing so it pushes the rod which in turn opens the valve allowing coolant to flow.
Regardless of whether the thermostat is a standalone device or one which is integrated into the thermostat housing, the operation is the same.

Why integrated?

Up until about 15 years ago all thermostats were standalone units that were installed into a housing. In the event the thermostat failed, the mechanic was faced with removing the housing first. Although it was not overly difficult to change a thermostat, the problem was that the housing often failed due to overheating. It was never a problem for a mechanic to locate a thermostat but locating the correct housing was often difficult and costly.
With the introduction of integrated units where the thermostat and the housing were one, there is no problem. The mechanic can quickly and easily replace the entire unit, it takes no special tools and as the thermostat is fixed permanently into the housing there is no fear of it being installed incorrectly.

Mechanics favor an integrated thermostat housing:

In the event there is need to replace the thermostat, integrated designs make the replacement job much simpler. Twenty-five years ago vehicle manufacturers began to understand this and started fitting them at the factory; today they are almost in universal use. The primary beneficiary is the mechanic; he can now replace the thermostat quickly with no fear that in the process the housing may be broken or damaged.