> Since it is a closed system the increasing pressure of
> expanding coolant would blow a hose loose. So at 15 psi the pressure cap is
> supposed to open and allow coolant to flow into the overflow tank. When the
> engine begins to cool after shutdown, the coolant shrinks, reducing the
> pressure and back-suctioning coolant from the overflow tank back into the
> expansion tank.

Am I correct in thinking that the system pressure should be zero when
completely cold?  Reason I ask is that I've been fixing one leak after
another-frnt heater valve, rear heater valve, heater core, bleeder
valve, expansion tank and others.  While removing my transmision the
other day,  I removed a hose for access and coolant came shooting out
fully pressurized.  This is after the van had been sitting for two days.
Is my expansion tank cap bad, letting fluid in but not out?  Or am I
looking at an internal head gasket leak(hope not because I just had the
heads redone 6K miles ago)?  Any other ideas?

Garrick
84  Westy
Davis, CA