there is a traditional and standard booster function test.
easy to do and that would be a good test on the booster.
I seldom ever find a bad booster.

but plenty of master cylinders, and they can leak between the two chambers
internally, and not work right, even though no fluid comes out anywhere.
another 'for sure' on if a master cylinder is worn out is any signs of brake
fluid on or in the booster.
that usually points to a worn out master cylinder.

I think you just buy a rebuilt, new, or used booster. Not the kind of thing
usually rebuilt at home, or even in a regular car shop.
Scott
turbovans

----- Original Message -----
From: "Jim Johnston" <inmytree1@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, August 09, 2009 5:26 PM
Subject: Re: Problem with brake

>I say it's the master cylinder.  Had the same issue with my 91 Gl.  A new
> master cylinder solved the issue.
>
> Jim
> Wilmington, NC
>
>
> On Sun, Aug 9, 2009 at 7:55 PM, Gilles H Turmel
> <gilles.turmel@sympatico.ca>wrote:
>
>> A friend of mine has a 91 Wesry GL auto with a 2006 EJ25 engine. He has
>> to
>> pump the brakes at least twice to get a decent result.  Hi hydraulic
>> fluid
>> level is stable. Does he have a booster problem?  If yes can that booster
>> be
>> rebuild?
>> Best regards.
>>