Brake advice?

Hi -

I have a 1976 corvette that I am trying to keep going on a minimalist budget.

BSAKing wrote:
> Hi -
>
> I have a 1976 corvette that I am trying to keep going on a minimalist
> budget.
>
> I have a brake issue in that I am losing brake fluid - a lot from the
> rear reservoir and little from the front. I have not pulled the
> wheels and calipers yet, but I did notice that after a little spin
> around the court here that there appears to be some fluid collecting
> and running out of a machined hole maybe about 1/8" on the bottom of
> the Master brake cylinder that seems to go right through the
> cylinder, just in front of the brake booster.
>
> Does this seem indicative of a faulty master brake cylinder?
>
> I have no doubt I have slight seepage from the calipers and I intend
> to replace the seals, but it is a lot of fluid going missing in a
> short time, so I suspect more than one issue.
>
> Thanks for any clues.

The fluid has likely gotten into the booster as well and
destroyed it. Better check.

"BSAKing" wrote:

> I have a 1976 corvette that I am trying to keep going on a minimalist budget.

> ...there appears to be some fluid collecting and running out of a machined hole
> maybe about 1/8" on the bottom of the Master brake cylinder that seems to go
> right through the cylinder, just in front of the brake booster.

http://www.rockauto.com/info/Raybestos/MC36367-7.jpg

That little hole just below the "snout"?

When the seals go bad on the primary piston (the shiny silver inside the snout),
fluid will leak out and collect between the master and the vacuum booster. The little
drain hole is there to *try* and keep the fluid from building up in the gap and being
forced (or sucked) past the booster's seals, slowly filling the internal chambers with
fluid and eliminating the "boost" part of "vacuum booster".

Time for a new master, and as suggested, check the booster for fluid inside, or any
air leaking in/out around the booster's front pushrod seal.

On Monday, March 11, 2013 4:42:05 AM UTC-4, Sanity Clause wrote:
> "BSAKing" wrote:
>
>
>
> > I have a 1976 corvette that I am trying to keep going on a minimalist budget.
>
>
>
> > ...there appears to be some fluid collecting and running out of a machined hole
>
> > maybe about 1/8" on the bottom of the Master brake cylinder that seems to go
>
> > right through the cylinder, just in front of the brake booster.
>
>
>
> http://www.rockauto.com/info/Raybestos/MC36367-7.jpg
>
>
>
> That little hole just below the "snout"?
>
>
>
> When the seals go bad on the primary piston (the shiny silver inside the snout),
>
> fluid will leak out and collect between the master and the vacuum booster.. The little
>
> drain hole is there to *try* and keep the fluid from building up in the gap and being
>
> forced (or sucked) past the booster's seals, slowly filling the internal chambers with
>
> fluid and eliminating the "boost" part of "vacuum booster".
>
>
>
> Time for a new master, and as suggested, check the booster for fluid inside, or any
>
> air leaking in/out around the booster's front pushrod seal.
====================
Thank you very much - that makes perfect sense.

I pulled it off and the pushrod came out with it - It appears to have a small spline on the front that was stuck a bit with age. There is no damage to the seal, it is still supple and there is no fluid behind it. It does not appear to be a pressure fit or anything - just a seal held in place by the bolting together of the two pieces.

I experienced no symptoms that I had read elsewhere of a damaged or malfunctioning booster, so I think I can assume all is ok on that front.

My parts guy here has suggested a Cardone 10-1423 as a replacement. 1976 was a transition year - I ran into that issue on another repair I had to do previously - mine has no bleeder screws on it, but I am not sure if that Cardone unit has the drain hole. It certainly seems like a good idea on the basis of this experience. I'll check that Raybestos unit out further.

On 03/10/2013 06:56 PM, BSAKing wrote:
> Hi -
>
> I have a 1976 corvette that I am trying to keep going on a minimalist
> budget.
>
> I have a brake issue in that I am losing brake fluid - a lot from the
> rear reservoir and little from the front. I have not pulled the
> wheels and calipers yet, but I did notice that after a little spin
> around the court here that there appears to be some fluid collecting
> and running out of a machined hole maybe about 1/8" on the bottom of
> the Master brake cylinder that seems to go right through the
> cylinder, just in front of the brake booster.
>
> Does this seem indicative of a faulty master brake cylinder?
>
> I have no doubt I have slight seepage from the calipers and I intend
> to replace the seals, but it is a lot of fluid going missing in a
> short time, so I suspect more than one issue.
> Thanks for any clues.
>

Entirely possible that the fluid is leaking from the back of the MC into
the booster. You won't see it dripping on the ground because it'll be
sucked into the intake and burned by the engine.

I'd just pull the MC slightly away from the booster and inspect; if
there is any evidence of leakage then rebuild/replace the MC.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On 3/10/2013 12:56 PM, BSAKing wrote:
> Hi -
>
> I have a 1976 corvette that I am trying to keep going on a minimalist budget.
>
> I have a brake issue in that I am losing brake fluid - a lot from the rear reservoir and little from the front. I have not pulled the wheels and calipers yet, but I did notice that after a little spin around the court here that there appears to be some fluid collecting and running out of a machined hole maybe about 1/8" on the bottom of the Master brake cylinder that seems to go right through the cylinder, just in front of the brake booster.
>
> Does this seem indicative of a faulty master brake cylinder?
>
> I have no doubt I have slight seepage from the calipers and I intend to replace the seals, but it is a lot of fluid going missing in a short time, so I suspect more than one issue.
>
> Thanks for any clues.
>

The good news is that your problem is obvious. It's obvious that your
master cylinder is leaking and has to be replaced. You could probably
buy a rebuild kit and replace the seals for hardly any money. Ditto for
the calipers. I enjoy doing this kind of work. Have fun!

On Tuesday, March 12, 2013 2:37:38 PM UTC-4, dsi1 wrote:
> On 3/10/2013 12:56 PM, BSAKing wrote:
>
> > Hi -
>
> >
>
> > I have a 1976 corvette that I am trying to keep going on a minimalist budget.
>
> >
>
> > I have a brake issue in that I am losing brake fluid - a lot from the rear reservoir and little from the front. I have not pulled the wheels and calipers yet, but I did notice that after a little spin around the court here that there appears to be some fluid collecting and running out of a machined hole maybe about 1/8" on the bottom of the Master brake cylinder that seems to go right through the cylinder, just in front of the brake booster.
>
> >
>
> > Does this seem indicative of a faulty master brake cylinder?
>
> >
>
> > I have no doubt I have slight seepage from the calipers and I intend to replace the seals, but it is a lot of fluid going missing in a short time, so I suspect more than one issue.
>
> >
>
> > Thanks for any clues.
>
> >
>
>
>
> The good news is that your problem is obvious. It's obvious that your
>
> master cylinder is leaking and has to be replaced. You could probably
>
> buy a rebuild kit and replace the seals for hardly any money. Ditto for
>
> the calipers. I enjoy doing this kind of work. Have fun!

Yes - I dropped a new master into it today after priming/purging it on the bench. So far so good. Never done it before, but I have brakes, so that looks promising.....

When I get a bit of time I'll jack it up and tear the front tires off and examine the calipers and probably end up with new seals (if there is no pitting)and pads.

On 3/12/2013 1:03 PM, BSAKing wrote:
>
> Yes - I dropped a new master into it today after priming/purging it on the bench. So far so good. Never done it before, but I have brakes, so that looks promising.....
>
> When I get a bit of time I'll jack it up and tear the front tires off and examine the calipers and probably end up with new seals (if there is no pitting)and pads.
>

Good for you. I've had the master cylinder fail on me twice. I'm not
sure how that happens. It is not a good thing.

The first time it happened I panicked and just stood on the brake the
whole time. Luckily there was a sturdy tree conveniently nearby. These
days I know the correct procedure is to pump them brakes!

This was for a Chrysler mini-van. I replaced the master cylinder but the
funny thing was that the rebuild was faulty too. The parts guy replaced
it with no questions. Hopefully, they got a more reliable supplier.

On 03/12/2013 07:42 PM, dsi1 wrote:
> On 3/12/2013 1:03 PM, BSAKing wrote:
>>
>> Yes - I dropped a new master into it today after priming/purging it on
>> the bench. So far so good. Never done it before, but I have brakes, so
>> that looks promising.....
>>
>> When I get a bit of time I'll jack it up and tear the front tires off
>> and examine the calipers and probably end up with new seals (if there
>> is no pitting)and pads.
>>
>
> Good for you. I've had the master cylinder fail on me twice. I'm not
> sure how that happens. It is not a good thing.
>
> The first time it happened I panicked and just stood on the brake the
> whole time. Luckily there was a sturdy tree conveniently nearby. These
> days I know the correct procedure is to pump them brakes!
>
> This was for a Chrysler mini-van. I replaced the master cylinder but the
> funny thing was that the rebuild was faulty too. The parts guy replaced
> it with no questions. Hopefully, they got a more reliable supplier.

Oddly enough, one of the most common ways for a master cylinder to fail
is after other brake work - at least if you pump-bleed the brakes. What
happens is that the seals in the MC wipe over an area that they haven't
traveled over in literally years, and a slight buildup of corrosion
and/or pitting can rip up the seals in the MC and cause them to fail
shortly thereafter. I've had that happen to me on two different
vehicles... then I got smart and bought a pressure bleeder and haven't
looked back. Pressure bleeders are wonderful things!

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On 3/12/2013 2:15 PM, Nate Nagel wrote:
>
> Oddly enough, one of the most common ways for a master cylinder to fail
> is after other brake work - at least if you pump-bleed the brakes. What
> happens is that the seals in the MC wipe over an area that they haven't
> traveled over in literally years, and a slight buildup of corrosion
> and/or pitting can rip up the seals in the MC and cause them to fail
> shortly thereafter. I've had that happen to me on two different
> vehicles... then I got smart and bought a pressure bleeder and haven't
> looked back. Pressure bleeders are wonderful things!
>
> nate
>


Interesting. I have no doubt that you're smarter than I am. Maybe even a
lot smarter. :-) When I think about all that time I spent under cars
shouting "up!" and "down!" with my Mickey Mouse jar, trying to keep the
tubing in the bottom of the jar, it really makes me feel like a big
dufus. One time I drilled a hole in a bottle of brake fluid and stuck my
tubing in there. That was my pro setup. :-)

OTOH, bleeding brakes is pretty relaxing. I used to like laying with my
back on the cool concrete floor. Sometimes, I'd just fall asleep down
there. My friend would say "are you taking a nap"" and I'd wake up a
little disoriented. If it was me doing the pumping, I would have quietly
gotten out of the car, turned off the lights, and left... that would
have been funny as hell.