The heater core is in line with the engine, not the radiator, so it will show
the same pressure that's currently in the engine. The radiator doesn't have any
pressure until the thermostat opens.

PerL
87 Syncro 112i

Alistair Bell wrote:

> how about "T"-ing into the cooling system at the bleeder screw on the
> radiator? Is the bleeder screw a National Pipe Thread or something else? If
> it is NPT then it would be straightforward to plumb in the pressure sender
> or tube.
>
> alistair