Thermostat Question

[islander]

A very quick question. Does the cooling system need to be running at pressure to get the thermostat to open.

Was running a test yesterday after replacing a blown fuse for the fan and noticed that the swan neck cap was leaking. Replaced that and new cap was working fine, when I noticed that the filler tank was venting out to expansion tank below it at low temperatures. I will replace the cap on Monday.

>>> Edited by islander on Sunday 27th June 13:41

[Gerry Attrick]

No. The thermostat will operate providing there is hot water, above the opening temperature, at the sensor. If the pressure cap is venting at low temperatures, but above ambient, you probably have air in the system (they all do that, sir!), which is expanding and pushing out the coolant.

[rev-erend]

I agree with Gerry .. thermostat does not need pressure to open.

Also - make sure the swan neck cap in plain car
(not spring loaded pressure cap !).

[Rus Wood]

Also check that the thermostat jiggle pin is at the top.

The thermostat should have a small hole in it which prevents the formation of air locks (an air lock around the thermostat bulb could cause it to heat very slowly. The thermostat in the RV8 is quite high in the engine so is prone to forming these airlocks. The air from the top of the inlet manifold should find its way through the hole in the thermostat and via the top hose to the top of the swan neck.

This hole should be at the top of the thermostat to minimise the air lock. It has a jiggle pin in it just to break the surface tension of the coolant.

By the way whenever I check the water level in my car I always find air in the top of the swan neck - always have. The engine hasn't had any overheating or water-loss problems. I tend to ignore the swan neck now and just top up the bottle to the pip on the level indicator. If I do this it has always managed to use about 1/2 pint (or less) per 1000 miles.