Date: Sun, 22 Mar 2009 18:46:30 -0700
Reply-To: neil N <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil N <musomuso@GMAIL.COM>
Subject: Re: another brake saga
In-Reply-To: <20090322214126.DD9591E8130@tc2.main.nc.us>
Content-Type: text/plain; charset=ISO-8859-1
On Sun, Mar 22, 2009 at 2:39 PM, Edward Maglott
<emaglott@buncombe.main.nc.us> wrote:
> I was having wonderful brakes after replacing my master cylinder a
> year or so ago. Apparently I had been driving around with little or
> no pressure to my rear brakes for a while. All was well in the brake
> department until I started losing fluid. Then I started losing fluid
> fast, and had very poor stopping power and a puddle at my right rear wheel.
>
> Rear wheel cylinder failure, drained all the fluid out of that
> circuit and I know I pumped air into it. I also think the pedal hit
> bottom during this episode. Off to FLAPS for 2 new wheel cylinders
> and new shoes. Debated waiting and getting cylinders from BD or
> another list vendor, but was in a hurry to work on it while I had
> good weather. OMG what a mess on the side that had been
> leaking. yuck. Got everything cleaned up and put back properly and
> adjusted properly so the shoes were barely touching the drum. Bled
> the system with the old fashioned GF pumping the pedal method.
>
> Pedal remains soft. Meanwhile I score a cool pressure bleeder on
> Freecycle. So give that a try, didn't get any more air out. (Maybe
> a tiny bubble or 2.) I bled out about 12oz total which I think
> should be enough. No change in pedal. I review archives and read
> about bench bleeding the MC, which I did when I got the new one. I
> do this with it in the van. Just cracking the lines and trying to
> catch the fluid with rags. No change. I go for a drive on some
> gravel roads and find I can't lock the rear wheel with the
> brakes. Fronts do lock. On pavement I can't lock any wheel despite
> what feels like a LOT of pedal pressure. Can't really tell if I'm
> hitting bottom in that situation.
>
> I decided to pull the rear drums to see what is going on in
> there. Weird thing. On One of the new cylinders the piston toward
> the front of the van pulls back into the cylinder on it's own. I
> think it might be the rubber boot pulling it back. It goes slowly
> but ends up with a pretty big gap between it and the shoe. Up to
> about 10mm if you wiggle things and wait a couple minutes. I looked
> at the cylinder on the other side and it seemed to be fine.
>
> Questions: I'm thinking that on the first press of the brake pedal
> the rear circuit is going to spend all that fluid to push that piston
> out to the point where it touches the shoe and the rear brakes aren't
> going to do anything. Yes? How much fluid do I need to drain from
> the right rear wheel before I am sure I have bled the whole circuit
> from the MC to the wheel. How much for the front? Bentley mentions
> pushing a lever on the brake pressure regulator, but there is none on
> my '86. I remember other VWs having the kind with the lever, is this
> just an error?
>
> Any other ideas appreciated and thanks in advance.
>
> Edward
>
FWIW, on my '81, and on the '85 I pulled the part off of, both
regulator valves do NOT have the lever.
Are you certain you have the rear brakes assembled correctly?
i.e. if push/adjusting rod is installed incorrectly, a shoe(s) might
not be seating right. If so, it may stay too far out and not return
with the cylinder. Incorrect assembly of springs may be the issue too.
I suspect if the shoe(s) isn't seating right, it *might* have affected
the bleeding process, but I'm not certain.
Since you had a failure at a rear cylinder, and the brake pedal
travelled to the floor, if there was any amount of debris on the MC
wall, it's *possible* some internal parts got scored.
Quite UNlikely IMO considering MC is only a year or so old though.
Neil.
--
Neil Nicholson '81 VanaJetta 2.0 "Jaco"
http://tubaneil.googlepages.com/
http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
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