I'm going to guess this was on a pre 87 model. In any case ZERO coolant
should flow through the vale when it is closed. If not, it is a bad
valve, new or not. Any tiny leakage is most noticeable in 87+ since
these have a different dash air flow path. Before then the main dash air
vents carried only outside air, fresh. The 87+ pass this air through the
heater core at all times. In summer this makes even small leak of
coolant  heat this air to an annoying degree. I have replaced
internally leaking heater valves on many Vanagons, a recently as a few
weeks ago. You should be able to blow ZERO air through a new one. Take
it back if a new one allows any flow when closed.

Mark

Roger Sisler wrote:

>Hello, I once thought I had a problem with this heater control valve. Took
>it out to see. I could blow through it when closed, so I thought it was
>bad. I was wrong. The replacement valve also allowed me to blow through it
>when closed.I cant explain this, but I put the old one back in and just
>adjusted the cable,and all was well.If it is leaking externally it may be a
>bad valve. Like said above, adjusting the cable is a bear.I think this
>adjustment is near the radio. The heater vent flaps are removable. Look
>closely at them and you will see a little black plastic clip that can be
>removed. The vent flaps then drop out. You can reapply a foam seal(bus
>depot?) for good vent closing in winter and summer.Pray that you dont have
>to remove the lower dash cover.I think that when it was designed, they
>confused this with a security seal. You will most likely have to break it
>to remove it.
>
>
>