A friend's '83 vanagon w/transplanted diesel jetta engine suddenly is overheating. Appears there is no circulation to rad at front of vehicle- removed two rad hoses at front and blew- clear; pump seems to move fluid with hoses off; no thermostats evident;
Any Ideas?

Okay- first water cooled VW I've worked on, and the thermostat is on the pump. Still, as long as the heater was blowing hot air, it would cool the rig sufficiently, so my diagnosis, thus far, stuck thermostat and air lock- more soon()
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just a guess, has the rad been drained and replenished of coolant?
http://www.dubnetworks.net/
there's some knowledge to be gleaned from these folks.

A quick check of the rad core, pour water in the top and see how fast it comes out the bottom. An air lock as you mentioned will stop flow. The thermostat must be replaced with the correct one on these engines, I assumed you replaced it. Water pumps were known for loose impellers. With the thermostat open and electric fan, on the temp difference across the rad inlet and outlet should be felt easily or measured with infra-red gun. Never had any experience with the Vanagon.Phil
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-Replaced thermostat with identical unit, reverse and forward flushed heater core, worked for a while then similar problems so I removed thermostat and no overheating, though possible underheating- women took unit to german mechanic for this and exhaust problems, and he didn't really solve the problem either.
I doubt the impeller is loose, having examined pump, and think possibly it is the wrong thermostat.
How to find Korrect one I don't know- as the year of the engine is not knowm. Could look for serial #s-
Have offered to re remove thermostat- This woman uses her vanagon as a delivery vehicle and it's been a hot spring around here.
Cheers all!
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Re the thermostat, an automotive supply store would probably tell you what variations there are. The serial # is at the top of the block on the front side, just below the surface the cylinder head bolts on, roughly above the vacuum pump. The VW diesel parts forum or maybe VW dealer will tell you what cars and years that engine was in. The thermostat has a flange on the bottom side that closes off a port, so it does not look like most others. Some very hard to solve overheating problems have actually been air-locks. Overheating can be caused by a warped cylinder head, not uncommon to the VW diesel. What was once 1 problem may now have developed into 2 problems. Good luck, Phil