During hard braking, the BPV valve lowers the rear brake pressure to prevent rear wheel lock up. The Bentley has a testing proceedure with special equipment. But , this valve only lowers rear pressure during extreme braking.  
I suspect you still have to adjust the rear shoes out to the drums or it will seem like you have no rear brakes or air in the system. After the basic manual adjustment is made, the self-adjusting mechanism will take over from there.  
It's unlikely that the steel ball check valve in the BPV is frozen in the low pressure position since the ball has to roll up an incline which will only happen under hard  braking or driving down a very steep slope.

Robert  

1982 Westfalia

----- Original Message -----
Wrom: DADRZFSQHYUCDDJBLVL
Sent: Tuesday, March 05, 2002 6:53 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Brake proportioning valve (BPV) or pressure regulator question

        To the brakes gurus:

        I have a ' 90 Westy (USA version) and have checked the brakes:
*       Changed the slave rear right cilinder (it was leaking).
*       Changed the front pads.
*       Bleeded the system twice.
        But I�m still not satisfied, it feels like only the front brakes are
working.  
        Some years ago I had an ' 85 Transporter (German version) and did'nt
have  
        any trouble with brakes, as a matter of fact it performed quite
good. The rear  
        wheels only lockup once in a "panic stop" on a wet road.  
        Last month there were some postings refering to the (BPV), so these
are my  
        questions:   
*       Do all Vanagons/Transporters have that valve, or only USA models?
*       How can I tell if it is working the way it is supposed to?
*       If it's not working or clogged, what happens if I get rid of it?

Thank you in advance!

        Erick Faith ' 90 westy "ELKE"Get more from the Web.  FREE MSN Explorer download : http://explorer.msn.com