Two Thermostats

[Johntheo5]

My 2019, 65BHP (petrol) Polo, engine type AW1 CHYC, normally aspirated, has two thermostats located in the water pump housing, one opens at 87C and seems to be the "normal" stat for cylinder head & jacket cooling, the other opens at, I think. 97C, I have no idea what circuit, if any, this stat controls, the oil temperature is displayed but pretty sure there is no oil cooler/regulator on this engine, any ideas?.

 

[Burnerman]

I think the second thermostat will be to govern water flow into the water pump itself.....isolating the thing, if you get my drift.
It makes for a quicker warm up time, and there are several designs in circulation.
One device actually shrouds the water pump impeller itself - VAG CR Diesels.
John

 

[Johntheo5]

Thanks John, could be something like that I suppose, I'm aware of the shrouded pump design, I think this was ECU controlled via a lever to vary the pump flowrate, and were prone to jamming.

 

[norseman]

Thanks John, could be something like that I suppose, I'm aware of the shrouded pump design, I think this was ECU controlled via a lever to vary the pump flowrate, and were prone to jamming.

All more to go wrong

 

[Johntheo5]

I think the answer is, separate cylinder head and cylinder block circuits, cylinder head stat opens at the lower setting.

 

[Johntheo5]

Read all about it here.