The radiator does the cooling, if a good engine is running too hot (and the
coolant is full), then there are only two possibilities.

1. Bad radiator.
2. Coolant not getting to radiator (due to thermostat stuck clised, bad
water pump, clogged pipe, etc.).

 From your description, it sounds like you spent a lot of time and effort
on #2, at this point I'd take care of #1 by replacing that radiator. Sure,
it isn't cheap; but it's cheaper than replacing warped heads due to
overheating.

Good luck!

Tim

At 12:55 PM 9/5/2006 -0600, Edwin Francisco Canessa Amador wrote:
>I have an 87 Vanagon (manual transmission) since 1991 and I still love it.
>It has been 3 years already since overheating problems started. Engine has
>been rebuilt (about a year ago) and the problem still continues.  I have
>changed most parts related to the cooling system (thermostat, temperature
>sensors 1 & 2, coolant distributor, water pump, expansion tank, several tubes
>and pipes that looked oxidized or about to be perforated) almost everything
>except the radiator (original), although it has been examined and tested.  In
>order to maintain engine temperature to its upper limit, the radiator fan and
>the heating system have to be running and on all the time, which makes
>driving very uncomfortable. Does anybody have experienced the same problem? I
>have to acknowledge my ignorance related to car engines and mechanics so I
>cannot be more specific so far. Any suggestions, comments, advice, will be
>most welcome.