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