Thermostat: Description and Operation

GF20.10-P-3162MCC Component Description For the Coolant Thermostat








Shown on engine 132.930
1 Thermostat

Location
The thermostat is located in the direction of travel on the right on the engine block.

Task
The thermostat separates the large from the small coolant circuit for a cold engine. This ensures that the engine reaches its operating temperature quicker. As the coolant temperature increases the thermostat opens and coolant also flows through the large coolant circuit.







2 Expanding material
3 Spring
4 Metal can 5 upper plate
6 Rubber insert
7 Housing
8 Metal pin 9 lower plate
A Engine cold
B Engine warm
h Thermostat hub

Design
The thermostat mainly consists of an expansion element, a return spring and two valve plates. A special wax is used as an expanding material.

Function
On a cold engine the thermostat is closed and the coolant flows through the small coolant circuit.
As the coolant temperature increases the expanding material melts and presses against the rubber insert. The metal pin is pushed out of the rubber insert. The fact that this rests against the upper housing means that the whole metal can with both valve plates is pressed downwards.
At full stroke the lower plate closes the small circuit. At the same time the upper plate frees up the large coolant circuit with the maximum cross-section.
During cooling of the coolant the expanding material solidifies again and the spring presses the pin back. The large coolant circuit is finally closed.
The whole process represents a continuous regulating process for which the coolant temperature can be held constant with a precision of T ±5°C.