Our part built mk has a pinto installed alongside a golf radiator and some sort of VW (possibly golf also) header tank.

So far we have plumbed both large water pump connections directly to the radiator and blocked off the smaller (15mm?) outlet that I presume would have been for the heater originally (returning to the block via the original inlet manifold water jacket?). So now all that is left to do is plumb the header tank in to the top of the radiator. The VW item in question has the usual 15mm outlet at the bottom and a small connection at the top.

The thing is, the small connection is not a pressure release outlet (I assume the cap does this due to the mechanism that appears to be within it). I know that the bottom connection needs to go to the top of the rad, but what about the small top hose on the tank? Should it just be blanked off? If its not blanked or plumbed somewhere then of course the system will not pressurise.

you've got it the wrong way round.

the top connection on the expansion tank should go to the top of the radiator to allow air to escape from rad into tank. the bottom outlet should go from the tank to the inlet on the water pump. (water comes from the head/inlet manifold, through the heater matrix and back IN to the water pump on that 16mm union.)

tom

Thanks for the reply, that makes sense.

Can I run the lower outlet from the header tank into the 16mm inlet to the pump, or does it have to go directly into the bottom radiator hose? I only ask as I dont really have a decent bottom hose with T piece.

it's effectievly the same thing. the bottom hose and the 16mm inlet are on the suction side of the impeller in the pump so it makes no difference.

tom