I'm replacing the headgasket on my 1993 granada 2.0 DOHC, as the coolant is over pressuring in the header tank.

I was wondering if there is a bimetallic strip in the heater that only allows water/coolant to flow through when the engine is warm or is it more likely to be blocked. I know it isn't passing through as I checked the temps of the inlet and outlet by touch and the outlet was still cold. Also I've tried to blow through the pipework and had nothing come out either.

So is it a new matrix or is there a heat controlled valve?