[Vwdiesel] 9k rebuilt '82 Diesel Westy coolant temp rising, (fwd)

[Val Christian]

I had something similar, but not identical, and I seem to write (again) about
it every year.  I had a thermostat fail.  For a year or so the part which fell 
partially obscured the water flow, and the car was pleasantly warm inside
when it was -10F outside.

Then one night, at about +15F, the part made it's final journey to the 
impeller blades of the pump.  There it blocked total flow, and things
rapidly overheated.

So what is the chance you have a partial obstruction in your coolant
system?





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'82 Westy #2 has always had some bubbles in the coolant reservoir.  9000
miles on rebuilt 1.6NA.  

**Now it's "overheating" UNLESS I drive at high rpms.**

(Just getting 1/2 way to the red light, but I'm actively trying to keep
it low.  Idling down long downhills also drop the temps?!)

I do have a weepy return coolant pipe/hose connection in the engine
compartment.  No pressurization of the system - in fact I've used 4
different pressure caps and none push or suck into the overflow
reservoir!  Also no sign of exhaust gases in the pressure tank,
according to one of those diesel exhaust gas tester things.

Coolant pipe to radiator is warm, return pipe is cold, although the
return hose is warm (probably heat from the bottom of the coolant
reservoir??)

So...  

Bad water pump?  This is my first guess, But perhaps not because high
revs cool the system?  I can also see good? flow in the pressure tank.
Maybe a loose impeller! (it's the plastic/cast metal combo kind, yeah -
tell me where to get a better one!  Stamped??)

Bad thermostat?  Perhaps not because the outgoing coolant pipe is warm,
and things do cool off at high revs?

Clogged Radiator, Hmmm..  this seems like a possibility as well??  The
van did sit for 3 years, I cleaned the pipes and radiator, but there
could easily be residual gunk.

Air in the system?  Yes, this is how my head-gasket usually blow, or how
air works it's way out of the system, but only source I can find is the
weepy pipe/hose connection, maybe making itself into a one-way valve??
No signs of actual head gasket failure.

Bad injector spray pattern?  Well, they've only got 9000 miles on them.

Clogged air filter - 9000 miles?  I guess I'll replace it just in case?

Clogged Exhaust? - Dunno.  But high revs fix the problem?

It's COLD outside and I'm working in the snow, the prospect of working
on the cooling system is not a happy one.

Ideas?  Opinions?  What am I missing? I do have a '85 radiator and hoses
sitting in the parts pile, but...

Thanks,

Will in Alaska.

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