Brake experts?

"G.R. Patterson III" wrote:
>
> snh9728 wrote:
> >
> > I didn't mean an external leak; I meant a leaking piston seal.
>
> If this is happening, I must have gotten something backwards when I rebuilt the
> master. I need to locate a schematic -- the rebuild kit didn't have one.
>
> George Patterson
> If a man gets into a fight 3,000 miles away from home, he *had* to have
> been looking for it.



Just for grins, I bleed opposite of conventional practice beginning with
the closest wheel cylinder to the master cylinder and work my way out.

If it still goes to the floor, you probably have a faulty when cylinder
that is not working properly. I had a similar problem with a Lark back
about eight years ago. I had a "gorilla grip" friend work the brakes
and he quickly cause the faulty cylinder to fail completely. Then it
was simply a matter of reassembling that wheel cylinder correctly and
the problem was resolved.


--
JT

Just tooling through cyberspace in my ancient G4

Grumpy au Contraire wrote:
>
> If it still goes to the floor, you probably have a faulty when cylinder
> that is not working properly. I had a similar problem with a Lark back
> about eight years ago. I had a "gorilla grip" friend work the brakes
> and he quickly cause the faulty cylinder to fail completely. Then it
> was simply a matter of reassembling that wheel cylinder correctly and
> the problem was resolved.

Well, that's easy enough to check. I can just pull each wheel in turn and see if the
cylinders are operating.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

"G.R. Patterson III" wrote:
>
> Grumpy au Contraire wrote:
> >
> > If it still goes to the floor, you probably have a faulty when cylinder
> > that is not working properly. I had a similar problem with a Lark back
> > about eight years ago. I had a "gorilla grip" friend work the brakes
> > and he quickly cause the faulty cylinder to fail completely. Then it
> > was simply a matter of reassembling that wheel cylinder correctly and
> > the problem was resolved.
>
> Well, that's easy enough to check. I can just pull each wheel in turn and see if the
> cylinders are operating.
>
> George Patterson
> If a man gets into a fight 3,000 miles away from home, he *had* to have
> been looking for it.



That's a slippery slope. The slightest brake pedal pressure will
probably "pop" the cylinder pistons. I prefer the gorilla grip method
which will also reveal any other weaknesses...



--
JT

Just tooling through cyberspace in my ancient G4

Grumpy au Contraire wrote:
>
> That's a slippery slope. The slightest brake pedal pressure will
> probably "pop" the cylinder pistons. I prefer the gorilla grip method
> which will also reveal any other weaknesses...

I'm having trouble visualizing this. Grip on what? Pumping the pedal has no effect,
so extra strength there won't change anything.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

"G.R. Patterson III" wrote:
>
> Grumpy au Contraire wrote:
> >
> > That's a slippery slope. The slightest brake pedal pressure will
> > probably "pop" the cylinder pistons. I prefer the gorilla grip method
> > which will also reveal any other weaknesses...
>
> I'm having trouble visualizing this. Grip on what? Pumping the pedal has no effect,
> so extra strength there won't change anything.
>
>


You mean that you cannot build up pedal after several pumps?


--
JT

Just tooling through cyberspace in my ancient G4

Grumpy au Contraire wrote:
>
> You mean that you cannot build up pedal after several pumps?

That is correct. In fact, there's a slight resistance on the first pump that
immediately disappears.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

G.R. Patterson III wrote:

>
> Grumpy au Contraire wrote:
>
>>If it still goes to the floor, you probably have a faulty when cylinder
>>that is not working properly. I had a similar problem with a Lark back
>>about eight years ago. I had a "gorilla grip" friend work the brakes
>>and he quickly cause the faulty cylinder to fail completely. Then it
>>was simply a matter of reassembling that wheel cylinder correctly and
>>the problem was resolved.
>
>
> Well, that's easy enough to check. I can just pull each wheel in turn and see if the
> cylinders are operating.
>
> George Patterson
> If a man gets into a fight 3,000 miles away from home, he *had* to have
> been looking for it.

be very very careful doing that as there's a fine line between seeing
the cylinders operate and watching the pistons fly out of the bores,
dumping brake fluid all over your new shoes and freshly painted backing
plates etc. etc. etc.

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

G.R. Patterson III wrote:

>
> Grumpy au Contraire wrote:
>
>>You mean that you cannot build up pedal after several pumps?
>
>
> That is correct. In fact, there's a slight resistance on the first pump that
> immediately disappears.
>
> George Patterson
> If a man gets into a fight 3,000 miles away from home, he *had* to have
> been looking for it.

Are you sure there's not a pinhole leak somewhere that you can't see?
If no, I would definitely suspect the master cylinder. A zero pressure
situation after several pumps is either the master cylinder or a leak
that should be visible (i.e. dripping)

nate

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

Nate Nagel wrote:
>
> Are you sure there's not a pinhole leak somewhere that you can't see?

No, I'm not. Now that school has started, I'm having trouble getting a helper to pump
the brakes. With new lines, I'm pretty sure there are no holes in them, but it's
possible that I have a bad fitting. I need to have Peter work the pedal while I crawl
around under the car.

> If no, I would definitely suspect the master cylinder. A zero pressure
> situation after several pumps is either the master cylinder or a leak
> that should be visible (i.e. dripping)

Thanks for the confirmation. I thought that might be the case -- guess I was hoping
for a miracle. Hope I can get at it before Winter sets in.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.

Sounds like there's a high spot that's trapping air in the system. Are
those wheel cylinders installed with the bleeder at the top so the
cylinder fills up properly? Is, perhaps, the auto sitting facing
downhill, with the master cylinder outlet lower than most of the
cylinder, trapping air in it?

The master cylinder cups should face cup-side forward.

There's another phenomenon that likely isn't present here, but
gives people fits: the shoes can hang up on the backing plates if
there's no spot of lube on the rub pads, and they won't return to the
anchor pin unless the car rolls along for awhile or goes over a bump
or two. Adjusting the brakes forces the bottoms of the shoes out and
they seem to drag a bit OK and there's good pedal, but after a few
minutes on the road the pedal will go to the floor. No amount of
bleeding will fix it. You have to bang the backing plates with a
hammer to settle the shoes before adjusting the brakes.

Dan