RMS73

Just installed a GM vacuum operated valve in the water hose supply to the heater core. Trying to prevent hot water flowing to the heater core while the AC is on. While the engine is running and after it is turned off, water drips out of the bottom side of the diaphragm housing, there are several small holes in the molded piece. The valve is installed so that the water comes into the higher port and the water flow matches the arrow on the valve.
Have I installed this valve backwards or is the valve bad?
Roger

Diode

Sounds like the diaphragm/seal is punctured or otherwise defective. Can you test it out of the car?

RMS73

Tested in my garage sink, it still leaked.

Roger