Engine fan and thermostat

[CHIPZX81]

Following on from my previous Q re. overheating probs.

In my previous car (fiat) when the engine temperature reached a certain threshold the radiator fan would start up even if the ignition was turned off at that point, there was no fan belt it was powered direct by an electric motor. The C180(95)'s fan runs with the engine via a belt so if the ignition is turned off so is the fan - right? What role does the thermostat play in all this? I think the thermostat opens up fully at 105 degrees but what does that mean, does the fan run quicker when the thermostat is fully open? I am confused.

 

[Brian WH]

The thermostat is there to keep the engine at the right temperature. It is closed when the engine is cold, and opens when it reaches running temperature.

The fan is there to cool the water down and stop overheating. If it runs electrically it will run on until the temperature is low enough to switch off. On none electric fan cars the fan is usually bigger and enough to keep the water cool only when the engine is running.

Is that clear as mud?

 

[kid-jensen]

CHIPZX81,

This should add to your confusion, there's also a thermostat in the fan hub.........

When the temperature is high enough, it allows a viscous fluid to couple two turbine-like fans to make the fan "cut-in".

You can test that the viscous unit is working by getting the engine up to a high temperature (100-ish) and switching off. If the fan stops within one (ish) revolution, it's probably OK. If it spins for a few seconds it's probably time to open your wallet.

As you can tell, there figures are only a guide, there's nothing hard and fast about engine cooling...........


New Viscous units are about a oner from Europarts.

 

[pluggers]

As it was suggested to me when mine broke, why not do the carrot test when it is running at about 110 deg ?