First, thanks for posting your problem Tom.  Luck would have it, I read your
post after having the same exact issues/symptoms this weekend - water
pouring out the back of the van after a long drive, but no indication from
the temperature gauge that the van was overheating.  In addition, I could
hear a hissing sound coming from somewhere around the pressure tank, but it
was all a mystery to me.

I bought a pressure cap today for $15 bucks based on Scott Daniel's advice
and low and behold the problem is solved! Big thank you's to you both...

Marc

On Mon, Aug 22, 2011 at 11:46 AM, Scott Daniel - Turbovans <
scottdaniel@turbovans.com> wrote:

> that blue pressure cap ..
> is my first thought.
> They are not that reliable.  One should always carry a spare.
>
> right now, with no further information or test results..
> it sounds like ..
> either pressure cap is not holding pressure properly .....
>
> or cooling system pressure is abnormally high ( such as combustion gases
> getting into cooling system at the heads or head gaskets ).
> If you see bubbles btw...
> rising to the surface of the coolant in the pressure bottle
> ................unless you are in the process of just filling the coolant
> to
> start with ..........that is not a good sign.
>
> if you *always* see a small bubble trail there ...
> that's really not a good sign.
> Have the air space above the coolant in the main pressure bottle sniffed
> with a smog sniffer. If there are excessive HC's there ....it's a
> combustion
> gases getting into the coolant issue.
> It should not do what you are descibing at all.
> Try the cap first though ..
> as it's so easy to do, and they are known to be a bit dodgey at times.
>
> Scott
> www.turbovans.com
>
>
> ----- Original Message -----
> From: "Tom Rowsell" <86westy@GEOEXPLOITS.ORG>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Monday, August 22, 2011 11:08 AM
> Subject: Coolant Strangeness
>
>
>  This is likely an FAQ...I'm on the road and searching is awkward with
>> cell phone.
>> It seems when I drive for an hour or so at highway speed, and stop
>> abruptly (to get gas for example) coolant rushes from the left tank
>> into the overflow one on the right, sometimes overflowing that one
>> onto the ground. In one instance the dash light began to flicker and
>> when I pulled over, the right hand tank was full, and the left one was
>> down 1/2 litre or so. It's not overheating, but temperature rises at
>> idle after a highway run.
>> 2.1 litre, recent (last 6 months) new rad, water pump. There are no
>> evident leaks, and oil on dipstick looks clean.
>> Any suggestions on what to check?
>> The needle is generally parked right at the center of the LED...
>> Thanks
>> Tom
>>
>