The bubbling indicates a bad pressure cap and or combustion gases
getting into the coolant, unless you have actually over heated. Try
replacing the pressure cap. If you still see bubbling after a few
heating/cooling cycles, then most likely you are getting gasses into the
system. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of John Smith
Sent: Wednesday, September 07, 2005 11:58 AM
To: vanagon@GERRY.VANAGON.COM
Subject: overheating issues

Hi Folks,

I�ve got a 91 Westy with about 5k on a rebuilt engine from NW Connecting
Rod
in Seattle.  Everything is running great, except for a mild overheating
problem.  I say mild because nothing has blown up or seized yet, and I
haven�t encountered massive amounts of steam or smoke coming from the
engine
compartment.  Here�s what�s happening:

During normal conditions in the last 750 miles or so, the temp gauge is
running at about 5/8.  When I use the A/C, the temp gauge goes up to �,
and
the light begins to blink.  Same thing happens when I�m climbing steep
hills, or in heavy stop-and-go traffic (The good thing is that the fan
seems
to be turning on normally when it reaches this level).  When I pull
over,
let it cool down and inspect the van, occasionally I�ll see the overfill
tank bubbling out very light amounts of coolant.  I�ve also taken off
the
grill and felt around my radiator for any cool spots, which I did not
find.

I should also mention that the temp light will sometimes start blinking
under normal conditions as well, meaning that the temp gauge is at about
�,
driving on a flat road.

I recently took the van into the shop for a coolant system inspection.
There was a small coolant hose that needed to be replaced, which they
took
care of.  After that they replaced the coolant, bled the system and
pressure
tested it- all came back normal, but it�s still behaving in the same
manner.

From searching the archives, I know that this could be caused by a
number of
things, including the water pump, thermostat, and radiator, and god
forbid,
leaking head gaskets.  But here�s what else I know:

*The fan switch and sensor have all been replaced very recently.  It
doesn�t
seem like I�m having any trouble in this department.

*A good portion of the cooling system hoses have also recently been
replaced, although the radiator has not.

*The 80 degree Thermostat and water pump were replaced 5k ago when the
rebuilt engine was put in, although I suppose these could be faulty.

The only thing I can tell from all of these observations is that the
coolant
sensor is going bad, but from what I�ve read, that�s rarely the case.
I�ve
also thought of the worst case scenario where the head gaskets need to
be
redone, and I have to go back to NW Connecting Rod and tell them to live
up
to their 12k warranty.  Before I go this far, though, does anyone have
any
ideas on what else to check or remedy?  Thanks in advance.

Cheers,

John
91 Westy