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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
Silly question, but are you sure H20 isn't leaking from your hose clamps?
If you do have pin-holes in the diaphram housing, sounds like the part is shot. Originals are pretty heavy brass const., so dunno why, or how it'd corrode like that. I would think that it would REALY leak under pressure and be very noticable if holes were present. Hence the guess that it's the clamps. I remember mine leaked until I got them seated good enough.
I checked the entire hose with a mirror and found no leaks except at the one hole on the bottom side of the diaphragm housing.
These holes are not pin holes, then are 1/16" in diameter and there are four of them. I assume they are weep holes to indicate the valve top seat is bad.
Roger
You may have a misunderstanding of the primary purpose for the holes if they are regularly spaced and obviously made into the part. Typically all vacuum actuators have vent holes opposite the vacuum side to allow atmosphereic pressure to move the actuator. I would expect heater valve failure to become evident as failure to operate rather than leakage. I would triple check the end connections; water leaks can be tricky to find.
I checked the hose connections and retightened the clamps twice. I connected the valve to my sink and verified the water was coming from the diaphragm area.
I am just making sure that the valve is sealed at the top so that it is to be able to contain the water when the inlet is on the top connection. This is the econd of the plastic bodied water valves that has leaked.
Roger
Roger, sounds like you just may have a bad valve (plastic bodied? Whut thuh?!!). The only way water can get into the actuator is that the seal on the actuator shaft is leaking. See Dr. Rebuild if you want to try an "old-timey" metal bodied valve; see the link below. Plastic is easier and cheaper to manufacture, but as a replacement for steel, it may be a marginal performer in ways the engineers didn't anticipate.
To confirm you have the flow direction right, consider my 70 w/AC has the water shut-off valve on the hose supplying water to the heater core (inboard core pipe). This hose comes off the intake manifold fitting, and I believe it is 5/8" diameter. The return hose from the core (outboard core pipe) goes to the water pump fitting. I can't believe it will make any difference if a seal is leaking.
I had several of the replacement plastic valves on my 78. One melted when it was a little too close to the exhaust and the other leaked just like your is. I found one in a parts bin that was only a little rusty, cleaned and painted it and haven't had a problem since. You never go wrong with the right parts.
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