On Sunday, March 10, 2013 11:02:32 PM UTC-4, Dad wrote:
> "BSAKing" > wrote in message
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> On Sunday, March 10, 2013 7:31:56 PM UTC-4, Dad wrote:
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> > "BSAKing" wrote in message
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> > ...
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> > Hi -
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> > I have a 1976 corvette that I am trying to keep going on a minimalist
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> > budget.
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> > I have a brake issue in that I am losing brake fluid - a lot from the rear
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> > reservoir and little from the front. I have not pulled the wheels and
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> > calipers yet, but I did notice that after a little spin around the court
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> > here that there appears to be some fluid collecting and running out of a
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> > machined hole maybe about 1/8" on the bottom of the Master brake cylinder
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> > that seems to go right through the cylinder, just in front of the brake
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> > booster.
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> > Does this seem indicative of a faulty master brake cylinder?
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> > I have no doubt I have slight seepage from the calipers and I intend to
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> > replace the seals, but it is a lot of fluid going missing in a short time,
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> > so I suspect more than one issue.
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> > Thanks for any clues.
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> > +++++++++++++++++++++++++++++++++++
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> > Not a low budget job, plan on 4 wheels (o-ring pistons and seals are best)
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> > and a master cylinder kit/replacement and emergency brake shoes or you
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> > will
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> > be doing some of it over later this year. New lines might not hurt if they
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> > show deterioration. Can't say enough for getting the rotors to a good
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> > runout
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> > on all of them. Stainless steel emergency brake hardware for a fix it and
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> > forget it for the life of the car.
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> ==============================
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> Oh - yes - I figured on most of that. By low budget I meant avoiding the
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> re-sleaved stainless steel calipers if mine are still servicable and I can
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> get away with just a kit - have to see what I see - it may be just as cheap
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> if one considers the hassle to rebuild the entire caliper assembly all
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> around... (Once every 20 - 30 years whether it needs it or not...)....
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> I'm not a master mechanic, so this could be challenging.....
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> Someone on another group suggested I'd better check the booster as fluid may
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> have gotten in there and destroyed it. But it all works ok so far.... (Aside
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> from the leaks that is....)
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> ############################################
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> Not that tough, pull a caliper and see if there are rust pits in the bores,
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> if not you'll do fine. Don't forget new rubber hoses. You will learn to
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> swear or make good use of the trait if you have learned it at a younger age
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> when you tackle the emergency brake. Go to Wilcox Corvette home page and
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> download their instructions for the emergency brake hardware installation..
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> Do use the dental floss to do it as easy as it can be done.
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I was told :

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.

SO:

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 the Raybestos MC36367 unit out further.

Time for research on the e-brake, etc. Thank you very much for the expert advice!