If the system can't hold pressure due to any opening, the coolant will boil
upon engine shut down. This is due to the stopping of the coolant flow and
the fact that the heads and upper cylinder are well above the boiling temp.
This boiling cause uneven cooling of the heads and cylinders and can cause
things to warp and crack. The boiling also causes erosion of gaskets and the
aluminum adding to future head seal failures. It is very important that the
cooling system is properly maintained including inspection and regular
replacement of that coolant bottle. They are prone to crack from fatigue.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of Jeff
Sent: Friday, October 13, 2000 12:49 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Boiling coolant

I have an 84 Vanagon.  Today while driving I noticed in my rearview mirror
smoke coming out of my rear vents.  The engine seemed to run and sound
fine.  The temp gauge read normal ( although I'm not sure it works right
anyway). The electric fan was running up front. I went immediately home (
about 1/2 mile and shut it off).  I went to open the engine compartment and
could hear the coolant boiling.  All belts are inplace and seem tight.  The
coolant bottle is split at the seam and steam was coming out ( guess from
built up pressure).  Any ideas from the list would be helpful.  Thanks,
Jeff