While replacing my rad, I also removing my front heater control valve, since
I still seemed to be getting heat in the core even with the valve fully closed. I
had already checked that the control cable was closing it all the way.
Blowing in the valve shows that there is some leakage, but not a lot -
blowing as hard as I can produces a barely noticeable amount of air coming
out the other side. This doesn't seem like enough to cause the amount of
heat I'm getting in the core - enough that it's uncomfortable to drive when
hot out just from the air coming out of the vents with the fan off.

I recall others commenting on this valve leaking. How much does it have to
leak to be a problem? Is there some other explanation? Could reversing the
flow from the engine cause the problem? (I may have done this in error
when installing my TD).

Thanks.

Shawn Wright
http://members.shaw.ca/vwdiesels
'88 Westy 1.6TD 5 speed
'85 Jetta Diesel 1.6NA