Date: Wed, 1 Aug 2001 09:18:05 -0400
Reply-To: 72510.1173@COMPUSERVE.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Helen Fahy <72510.1173@COMPUSERVE.COM>
Subject: Re: Brake booster woes.
Content-Type: text/plain; charset="iso-8859-1"
> Volks,
> I have an issue with my brakes on my 81 westy. They work, but not as well
> as they should. No air in the lines, new components all the way around.
>
> Another listee has an 83 AC vanagon, that I have driven, and it is
apparent
> to me that I have a brake booster issue. There is a pressure loss,
> somewhere in it, or in the lines to it. I have looked over the plastic
> tubes, and see no evidence of cracks or wear points. The checkvalve as
What are the differences between your brakes and the other Vanagon?
> well seems ok. Is there a test that I can perform to test it before the
> removal process? It is a pretty decent sized job, and I just want to be
> sure before I tackle it.
With engine off, pump brake pedal until it is hard. This depletes the
residual vacuum assist. With you foot pressing on the brake pedal, start
the engine. The pedal should move towards the floor, slightly. The pedal
should feel slightly softer.
NOTE: I have a 1987 Westy, 2.1 waterboxer, so I apologize for any info that
is not appropriate to the '81 AC 'Gon. As these beasts are only OK to scary
as far as brakes go, I thought I would tell other listers what has helped
mine. There are a couple of guys that are looking at some real beefy front
disk brake setups that require 15" wheels. I have not heard if they
finished the mods yet. I will probably go this way.
Two things that are often overlooked on the 'Gon's brakes are the available
engine vacuum and the rear brake adjustment. The engine vacuum is the power
part of the power assisted brakes. Using the recommendations of Bob
Donalds, I reset the valves and picked up about 4" of manifold vacuum. On
power off coast down, just prior to applying the brakes, the engine develops
21" of vacuum and holds it until just about stopped and then it drops to
~14". Having the vacuum gauge on the dash helped in verifying Bob's
procedure. Many thanks to Bob Donalds!! Also for the Marvel Mystery Oil
prior to changing the oil!!
The rear brake cylinder/adjuster/pivots are poorly designed. With the
adjuster and the brake cylinder both acting on the upper brake pivot points,
the lower portion of the brake shoes never makes contact with the drum. I
believe that the rear shoe is the worst for not using the brake material. I
read, I think on the archives, about this and used the suggestion of using
washers to move the bottom of the rear shoe closer to the drum. If you look
at the bottom brake shoe pivot, it is made up of 3 pieces. The pivot main
body has two cylindrical projections that register the actual pivot points.
The pivot points are removable from the pivot body by simply pulling them
off. The pivot points are not screwed onto the pivot body. If these pivot
points have never been off this can be quite the job! The washers I
referred to are placed on the cylindrical projections of the pivot body.
The pivot point is then placed back on the pivot body. The assembled brake
shoes/spring/drum effectively captures the pivot points and included
washers. I based the number of washers I used on two things: maximizing the
shoe to drum contact area and keeping the rear pivot point on the pivot
body=:O I checked the contact area by repeatedly assembling the brakes with
different numbers of washers, applying the brakes and observing the
addtional scratches on the virgin brake material, repeat.
This made a huge difference to the pedal feel and the braking performance on
my '87 Westy. Not like the 930 brakes I transplanted to my old '74 911, but
significantly less scary than before.
I spoke to some old Formula Vee racers and there is a procedure/machine, not
sure which, for contouring the brake shoes to the drum that they used to get
the maximum contact area from the brake shoe. Even with the washers on the
rear pivot point, I only get 2/3 -3/4 of the shoe making contact with the
drum. But that is better than the 1/4-1/3 I started out with.
HTH and let us know what you found.
Joe Fahy
