nbhab, it reminds me of how my 89 jetta greaseburner died. I was having similar problems with it. Overheating, heater wouldn't work. It turned out that the small coolant hose that is the air vent off of the upper radiator hose plugged causing an air bubble in the coolant system. The air in the system was never able to get back to the high point of the compression tank. I figured it out, it was plugged right at the connection to the compression tank. Cut the bad inch off the end and suddenly all the coolant drained in the the engine from the comp. tank. Drove it for a few days, but unfortunately, I warped the head and lost the head gasket. It's okay though, it had 415K on it and the doors were falling off.