Cary, I have had personal experience with a water pump which had an impeller
intermittantly slipping on the shaft.  Operation would run along normally, until
suddenly it would go into an overheat condition when the impeller suddenly stopped
turning.  This was on a newly reconditioned pump from VW on a newly rebuilt long
block from VW.  The mechanics at the independent VW shop said that they had never
seen the condition before, but the people at the FLAPS said it does happen very
rarely.

Some people have had problems with clogged radiator cores shutting off coolant
flow.  This may be caused by leak sealant added to the cooling system over the
years which can eventually clog the tubes in the radiator.

If this were my vehicle, I would remove the radiator first and have it "boiled
out" at a radiator shop as a first step.  With the age of the vehicle, it probably
would benefit from this, even if it isn't the major cause of the overheating
problem.  The next thing I would do, is remove the water pump and see if the
impeller can be made to slip.  Examine the engine block area next to where the
impeller runs.  If it is scored, the impeller is the cause.

Chuck Hill

CARY CHIANG wrote:

> Dear Listees:
>   I recently purchased an '85 Westy that the PO had warned me had a tendency
> to overheat in traffic.  I have owned several mid 80's vanagons and am quite
> familiar with their cooling system and Bentley procedures, but this one has me
> baffled.  I 1st bled the cooling system per Bentley and got coolant flowing
> out of the radiator bleed screw okay.  After 10-15 minutes of idling, the temp
> gauge climbs to about 3/5 and the red LED begins to flash.  Increasing engine
> speed to 2-3K for about 30 seconds brings the gauge back to the halfway mark
> a