Welcome to the Corvette Forums at the Corvette Action Center!

76 brake problem

K

k9judge

Guest
Just put two new calipers on the front. The back two calipers were not touched as they appeared to be ok. Drove two weeks, then low pedal and brake light came on. Air seems to have gotten into the back brakes somehow. Any ideas how this could have happend? Back brakes were bled and pedal came back up and brake light went off.
Denny
 
W

wolf_walker

Guest
Did you bleed everything right when you put the calipers on the front?


If so, you may well have out of true disk's on the rear, that will cause pumping in the rear that can pull air in. It's a very "vette" thing...
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
K9judge,

Sounds like air in there. It seems like the brakes will start to fail after one or two other things go bad.

I would also take a close look at the master cylinder, and of course inspect those rear calipers. Something is letting air in.

Normally I would say that you are out of true round in the rear, but if they worked fine before the front failed, and you did not remove the rear rotors, then is must just be a typical failure.


Good luck.


BTW, my wife and mother in law use to raise beagles. Now, they do some part time judging at local/regional shows. Would K9Judge have anything to do with that too?
 

Nut

Well-known member
Joined
Oct 15, 2000
Messages
890
Location
Bowie, MD
Corvette
Vette-less for now
K9judge,

This sounds more like cavitating caliper pistons. One or more of your rotors are just ever-so out of round and this causes the pistons in your calipers to cavitate. And like Wolf said, it is a "Vette thing". The cavitating will cause air to be sucked into the calipers and yet not a leak anywhere. Having the rotors turned and trued to each bearing assembly should clear up the problem. This assuming of course the other items Chris mentioned are OK.

Good luck. It's not a hard problem to correct.

.............. Nut
 
W

wolf_walker

Guest
One thing I never quiteunderstood is exactly where it gets the air in at? You would think it would leak visably. Guess that's one or the reasons so many people overlook the rear rotors though...
 

Nut

Well-known member
Joined
Oct 15, 2000
Messages
890
Location
Bowie, MD
Corvette
Vette-less for now
Wolf,

The air gets sucked in at the rubber rings around the pistons. The newer O-Ring designs from Vette Brakes cures this problem. They are worth the small $$ to get. Haven't had a lick of a problem since.

........... Nut
 
W

wolf_walker

Guest
Well I figured it got in there.. :) Just how does it enter a solid piece of rubber that's fluid tight? I wouldnt think it could move the piston off canter enough, but..?
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Chevrolet issued a Technical Service Bulletin in 1982 (which isn't in any of the pre-1982 Shop Manuals, naturally) instructing dealers to use a silastic sealer in the piston grooves where the boot seal goes and on the outside of the boot seal where it presses into the caliper bore, to eliminate moisture intrusion past the seal that could cause corrosion and air intrusion past it that could cause a low pedal, any time they rebuilt Corvette calipers. The TSB was very specific about the importance of having the groove in the piston and the seal bore of the caliper absolutely clean and dry before applying the silastic sealer so it would adhere to those surfaces.

There was only one more production year left on that caliper design once they finally owned up to the corrosion and "air-pumping" problems with it, so they weren't about to do a redesign; the sealer application was the "field fix".
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Vetteskins

Advertise with the Corvette Action Center!

Double Your Chances!

Partners

Top Bottom