Your expansion tank cap is probably bad and not holding pressure.  Take
it off and try sucking through it (clean the coolant off first).  If you
can easily suck on it then it is toast and needs to be replaced.  Many
are in the condition and folks just don't know.  It is important that
they hold pressure because if not then the boiling point of your coolant
is lower than it should be so it will overheat easier.

Hope this helps,
Ken Wilford
John 3:16
www.vanagain.com

Michael Elliott wrote:
> I replaced the water pump in my 1.9L yesterday, a thoroughly pleasant
> task, and filled and bled the cooling system. I did it using TJ Hannink's
> "raise the rear" method as shown on
>
> http://www.vanagonauts.com/The-Contrarian-(easy)-Method194.htm
>
> After the last of the bubbles came out of the hoses into the reservoir, I
> filled it, then filled the overflow tank to between the min/max lines.
> Let
> the engine cool, and noticed that engine had sucked in a bit of
> coolant so
> I added a taste to bring the level back between the lines.
>
> Took the van for a drive last night, checked under it this morning, no
> leaks. Hurray!
>
> This morning, I saw that the coolant level was well above the max
> line, so
> I siphoned some out. Took it for another drive, let it cool for a couple
> hours, and it was above the max line again. Siphoned more out. I moved
> the
> van off the driveway and parked it on a hill, with its nose high to stop
> blocking the driveway. An hour later I noticed that there was coolant
> behind the van. The overflow tank was completely full!
>
> Moved the van to level, siphoned more coolant out, cleaned up the mess.
>
> At this point I've removed about 2 liters of coolant from the system.
> What
> the heck?
>
> --
> Mike "Rocket J Squirrel" Elliott
> 71 Type 2: the Wonderbus
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> KG6RCR
>
>