I have been wrestling with this problem all day and I can't seem to put my
finger on it, so I am turning to the list for help.  Here is the situation:

Installed a 2.1l waterboxer engine that was supposed to be running fine into
a '84 Vanagon.
Engine runs great but after about 10-15 mins of running gets hot and I have
to shut it down.
I installed a new waterpump (1.9l) and thermostat (Behr) when I swapped in
the engine as well as bled the system of air like I have a hundred times
before.
One hose (the one to the upper part of the thermostat housing) is getting
very hot, while the other hose (to the lower part of the thermostat housing)
is staying cool.
Radiator is staying cool to the touch to the point where the radiator fan is
not coming on even though the temp gauge says the motor is overheating.

Things I have tried so far:
1. Removed new thermostat and tested it in boiling water.  Opened at around
180 degrees F.
2. Flushed coolant system out with water.
3. Tried to switch coolant hoses to see if perhaps they had been connected
backwards (no luck).

The waterpump is spinning merrily and I seem to have pressure at the radiator
(because I can bleed the system there), but no flow through the radiator.
The engine case behind the waterpump was free of scoring when I installed it.

Anyone ever go through anything like this before?  My next step is to try to
install a known good radiator for another van.  I just don't understand how
the radiator could be bad.  The van only has 55k miles on it and the guy that
had it before me didn't complain of overheating.  Of course it sat with the
hoses unhooked for a few weeks and maybe some animal or bees decided it was a
good place for a new home.

Any ideas or thoughts would be appreciated.

Thanks,
Ken Wilford
http://www.vanagain.com
John 3:16
Phone: (856)-765-1583
Shop:   (856)-327-0027
Fax:     (856)-327-2242