Technical Thermostat

Is the thermostat on every engine the "in" or "out" or does it vary based on mfg.

 

On every Hamb friendly engine I have ever seen they are on the "out's side and usually in the thermostat housing where the hose that goes to the top of the radiator connects. As they act on heat expanding the material inside the pellet to open them they have to be on the "out" side. The inlet to the water pump being the "In" side. This is one of the better diagrams that relates to a somewhat traditional car cooling system that I have found

 

Thermostat ehh? Now there’s a umm, HOT topic. Hehe.