For those with an overheating problem, noticing a cool radiator, let me
relay an experience I had.

I had a problem with a brand new VW 1.9 rebuild, installed by an
independent shop, that would sporadically overheat.  It was burped and
purged to no end by the shop mechanic, who finally gave up and gave it
to me and said effectively " you're on your own, they all do it, they're
really no XXXX good, why do you insist on driving one of these anyway",
etc.

I took it, and drove it a bit.  You could be going down the road just
fine, and suddenly the temperature needle would start to climb and then
the led would light and blink.  And also, I noticed that the heater
output went from normal hot, to cool.  Hmmmm, the heater circuit is not
the same as the radiator circuit.  Hot engine temp, but cool everything
at the front.  Maybe the water stopped moving?  How could that be?

I took off the pump.  The rotor on the water pump could be turned on the
shaft with a little force.  It was slipping randomly after the engine
warmed up, thus stopping the pumping action.

I replaced the pump and everything has worked since then.  My mechanics
said they had never seen this happen before.  I let them hold the bad
pump, and play with it.  Their demeanor was interesting.

So if you're having a strange overheating problem that comes and goes,
and the heater/defroster heat output is also affected, think about this,
it's probably the cause.

Chuck Hill