Can anyone tell me what a thermostat does?

**twinxster** · 2nd February 2012, 21:15

Hi all, my temp gauge is not working and im hopefully getting my thermostat fitted this week. Another thing that doesnt work correctly is my blowers, on cold theyre warm. On cold number 4 its hot. I have no cold air atall. So after driving 20miles or so i have to close all the vents and open the window! Is this thermostat related??? The thermostat has 5 openings(or valves? dont know what youd call them) Can anyone tell me what each opening/valve does? So i can look out for anything else that might not be right with my car.

**twinxster** · 2nd February 2012, 21:25

[IMG]thermostat[/IMG]

**GazVXLINE170** · 2nd February 2012, 21:42

I controls and maintains the coolant temperature. It is a valve which is effectively stuck to a bit of wax. As the wax expands with temperature increase the valve opens. This lets coolant - which has passed through the water jackets between the cylinders - get to the radiator to be cooled. As the coolant from the radiator is returned to the header tank (expansion bottle) it will return to the engine at a lower temperature. This causes the wax to contract and the valve closes. This forces the coolant directly back to the header tank (instead of going through the radiator) after passing through the engine. The thermostat constantly does this to maintain optimum temperature. The wax however does become knackered and most are designed to fail open to stop engine damage with overheating.

A cold running engine is the sign the thermostat has failed open. This will cause a slight increase in fuel consumption. Controversally, a jammed closed thermostat will cause rapid engine overheating with inevitable consequences if engine is not switched off.