AC heater core blockoff valve leak rate?

[thehueypilot]

I was servicing the AC last night in my 68 and evacuated the system and filled it with 22oz of R134 but the system would not get cold. I checked everything and it all checked out good. The last thing I decided to do was to put a hose pinch pliers onto the heater core incoming line to see if that would help and it did. I checked the valve position and it was in the full off (closed) position. I took the valve off and if functions correctly but in the full off (closed) position you can still blow through it a little bit. How tight are these valves supposed to be? It does not appear the be worn or eaten away but does not stop the flow 100%.

 

[mlpdeals]

So was it at least cool without the clamp down on heater hose? Did you have the contols in Max cool/max fan? (I think that water valve only restricts at those settings but i am not 100% sure).
Was coolant flowing thru the expansion valve? Was the compressor cycling or just always engaged?

Had you already converted to R134?
Did you change anything out when you evacuated the sys?(dryer)
compressor oil and seals?

 

[valley82]

What were the suction & discharge pressures when it was operating?
If the system was operating properly at about 2200 rpm you should have 15 - 18 psi on the suction side and 150 - 180 on the dicharge side (depending on ambient temp.)
If you have a guage set you should see about ambient + 30 degrees.
R-134's heat transfer rate above 100 degrees f. falls off quite a bit but I'm assuming that you were not seeing triple digit temps. this time of year.
If the heater hose valve is bypassing enough to alter the temp at the supply air grille by more than a couple of degrees then you have a problem which will be intensified as the ambient air temp. goes up.

 

[thehueypilot]

Thanks for the replies. I overcharged the system before I realized it was not low and the valve was leaking. The system is a Classic Auto Air and it cools down to 40F when I pinch off the heater core hose. The valve is closed but is leaking a small amount past it which seems to be enough to heat up the core. Can a block off valve erode away in a couple of years to allow this much leakage? It looks normal inside but does not seal off 100%.