Here's my problem:

1974 Mazda 929.

Water pump has a screw in fitting on top of it.

the inlet manifold has the same type of fitting screwed into the side facing the firewall.

at the back of the inlet manifold there is a t-piece fitting that is near the strut tower.
The side of this T fitting that runs towards the radiator has a hose that goes to the fitting on top of the water pump.

I just need to know which heater matrix hose goes to what fitting on the inlet manifold. ie does the top heater hose from the matrix go to the T piece or does it go to the screw in fitting?

that is correct



T piece goes to top (where the valve should be on the matrix)

ah ha. thanks for that. I'm pretty sure there is no tap (ie to turn off the coolant flow through the heater core) but I'll have a closer look tomorrow.

Cheers

edit: just clued on, one of the controls on the dash open and closes a valve on the top pipe I think.