sure, there must be all kinds of adjustable pressure relief valves you could
adapt.
A common house water heater has one..
though I don't know what the pressure is.

I would engineer a whole new metal pressure coolant bottle..
with a pressure relief valve of your preference on it.

14psi ...the range that our vans use roughly .
is not that high actually.
In the 50's or 60's ...pressure caps may have been in the 6 to 8 psi range.
They crept up over the years.
I think some modern cars might be more like 18psi etc.

What I would do first then..
is install a Cooling System Pressure Gauge..
very useful actually ..
if pressure suddenly drops ...
you know there is a leak.
if pressure gets higher than regulated ..
then cap is probably not working ..
that's where I'd start.
becuase..
if you have a good temp reading ..
no level warning flashing happening..
and you are running at say 12psi ..
then you know you're good.

scott
www.turbovans.com
----- Original Message -----
From: "HotelWestfalia" <zolo@FOXINTERNET.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, September 07, 2011 9:31 AM
Subject: Pressure releife valve

Hi to all,

I was thinking, that it would be a good thing if we had a releife valve or
two on our coolant system to save the gasket or the hoses, or anything that
would suffer.  The cap on the pressure tank is not being able to deal with
disaster fast enough.
Any of you ever did such thing?
Was this ever initiated?
Is there anything on the market that can be installed?

Zoltan