thermostat

Will Reeve · Post by **Will Reeve** » Sat Feb 19, 2011 1:44 pm

Just bought a genuine Rover thermostat. Quality is as you would expect superb bit it also has a little hole and plunger arrangement I've not seen before. I also treated her to a genuine gasket, they may be a quid more but they are metal and foam...it looks like genuine parts are worth the extra here!

mgbv8 · Post by **mgbv8** » Sat Feb 19, 2011 7:35 pm

make sure you fit the stat with the hole and plunger at the 12 o'clock position in the housing so air can purge on startup.

Will Reeve · Post by **Will Reeve** » Sun Feb 20, 2011 9:33 am

It has an idiot proof "top" stamped into it

I was surprised they went to the effort with the ball. I presume it's to only allow air through it and not water during the warm up period when the 'stat is closed? I would have thought the water pressure would keep it closed when the water pump was running?

RoverP6B · Post by **RoverP6B** » Mon Feb 21, 2011 8:42 pm

Will Reeve wrote,...

I would have thought the water pressure would keep it closed when the water pump was running?

Hello Will,

It will. Thermostats equipped with jiggle pins have been around for many many years. It is there to prevent air from being trapped behind the thermostat. When the engine is off, any air that finds itself behind the thermostat can pass around the jiggle pin, which won't be pressed against the hole, and rise to the high point at the top of the radiator hose. Once the engine is running, coolant flow pushing in the direction of the thermostat will keep the pin pressed into the hole (that is the theory anyway) whether the thermostat is open or closed. In reality I expect a small percentage of coolant will pass around the pin prior to the thermostat opening.

Ron.