What is the smaller opening on the thermostat housing for?

[aussiesmg]

Yeah I know newbie question but I still need to to know and searching failed to locate

 

[iwashmycar]

i think its for one of the little hoses that goes to the water pump.

see it in there...
View attachment 339351

 

[aussiesmg]

I thought the outlets on the water pump were both for the heater, can anyone confirm

 

[BlownFiveLiter]

It's for the bypass hose that recirculates the coolant in the engine while the thermostat is closed. That way there's no hot spots and you get even heating of the coolant inside the engine, until it reaches operating temperature.

 

[aussiesmg]

OK, so it does go to the water pump, so where is the other heater hose location, my engine is a project and I got it in pieces so i didn't have the chance to see it together