Hi John,
   The Bentley gives the same specs and procedure for the early and late MY
caps even tho they don't look the same according to the illustrations.
   Assuming you don't have the Stant tester shown on page 19.18, you need an
extra expansion tank or the equivalent or perhaps you could do it right on
the van if you can find another practical place to pressurize the system.
Of course you need a pressure gauge and some way to attach it.
  The cap should allow pressure to escape when it gets into the range of
13-17 psi and should let coolant back into the tank when there is a partial
vacuum of 0.3-1.45 psi.  Instead of vacuum from the tank side, you could
apply pressure to the overflow tube.
  You did save that old cracked expansion tank, didn't you?  :-)

Larry A.

On 9/16/07, John Meeks <vanagon@gmail.com> wrote:
>
> Hi List,
>
> Is there a method for testing the coolant expansion tank pressure cap?
>
> we just drove Byron (85 GL) back up from his front hose breakdown (250
> mi), and the shop that replaced the hoses filled her up with some kind
> of stop leak and the cap is all gunked up.
>
> I'm wondering if a cap failure may have contributed to the hose blow
> but can't find any way to test the cap in the archives.
> --
> John Meeks
>
> Vanagon Rescue Squad
> http://www.vanagonauts.com/Vanagon_Rescue_Squad74.htm
>
> '91 Multivan, '85 GL
> Northern Michigan
> KC8ZFN
>