Let me start by thanking all of you for so much great information that has really helped me as a C3 novice.

Now, let me ask, are leaking brake calipers just a fact of life? I come from a Porsche background and properly rebuilt calipers with regular maintenance last for years without any trouble. I've personally rebuilt dozens with zero issues.

Bought my wife's '78 that included rebuilt calipers in preparation for the sale and the left front was already leaking. Bought O-ring kits from Lonestar, tore them down and all looked fine. Rebuilt them and now the right front is leaking.

Bought a '68 from a well known restoration shop that had installed new O-ring kits in the calipers in preparation for the sale and guess what? Right front already leaking.

I'm curious, is this just a C3 thing or is there a solution? I searched calipers and found lots of leaking stories but no regular solution suggested. Seems some of you just purchase new or rebuilt on a regular basis and accept the situation.

Thanks for any positive recommendations.

 

The simple answer is yes, the C3 Calipers have a short piston that after a bit of use allows the piston to **** a little sideways in the bore. I had all my Calipers overhauled due to weeping and one leaked continually when left sitting in my shed, I had another new kit installed and it did the same thing again, so I had it done a third time and the same happened! The only fix was to buy a new Caliper.

 

When I purchased my 77 way, way back when. (1980's). The right rear caliper had been replaced already, according to the stack of receipts I got with the car. A few years later, one of the fronts started leaking. So, in my infinite wisdom, I replaced 3 calipers. With stainless sleeved rebuilt units I purchased from a Corvette vendor probably early 90's.
The one I didn't replace gave me trouble just a year ago or so. Seems the one caliper the original owner had put on. Had one side sleeved and the other half not sleeved! WOW. it failed.
I purchased a rebuilt replacement that was supposed to be new. It was garbage and leaked within a month. I ended up rebuilding my old one using a O ring kit but replacing the o rings so I could run Dot5. No issues since. Those 3 I replaced back in the 90's? All 3 still fine. Replaced the lines to them a couple times now. That's it. So, it's not the design of the caliper. It's the jokers rebuilding them. And the quality of the rubber parts they are using.

 

The pistons only **** if the bore size is to large! The one I referred to above had piston to bore clearance in excess of .010". God can't get that to seal! It's really very poor rebuilding!

 

I’ve had good and bad calipers at times. If I see a leak then I have to fix them. The last set I bought through one of the corvette suppliers and they have lasted over 10 years. I’m getting ready to replace them this spring.

 

If the calipers are sleeved in stainless steel and O-ring pistons are installed coupled with rotors that have less than .005 runout, you should have years of trouble free miles. It helps if the brake fluid is changed every few years. I have 15 years on my 66 and got 20 years on my 68. Jerry

 

So to be clear, these are all sleeved calipers with the O-rings. The leaks are all coming from the seal between the caliper halves. When I disassembled the first ones I found crud and corrosion on the mating surfaces which I cleaned up with a wire brush and scotch Brites. The recess for the small o-ring looked shallow but decent enough to make the seal so I torqued them together and assumed it would work. The one that was leaking is now fine but the other one that wasn't leaking is now leaking. I don't want to go through this again so I'd like to find a source for reliable, well built calipers. I'm guessing Lonestar will be my best bet..

 

I have rebuilt (over and over) the same four calipers that came with my car and that has worked out well enough for my use. The calipers on my C3 had been sleeved like most brake calipers out there by now. I was lucky with the stainless sleeved bores on the set I have. The factory style seals were in okay/good shape when I took them apart the first time but now I am using the O-ring style seals and they have been great and leak free for many years. Even with periods of sitting they are still working and function like they should. It is time for flushing both Corvettes brake brake fluid this spring.

Flushing your brakes is something that NEEDS/HAS to be done like every 5 years at a minimum. If the fluid has been flushed like it should the corrosion problems might be less common. If the previous owner has flushed the brakes then you might be in luck. Why do so many of us let our brakes go for 10 plus years on the brake fluid? It sits there sucking in the moisture and then it builds up and rusts starts.

Who actually LIKES Flushing the Brakes? Let alone like every five years?? I certainly did not relish the fun and time it took to do the job by myself and then having to get help to bleed the brakes. Then I read about the Phoenix Reverse Bleeder system, it sounded a bit too good at first. Then I bought one of their kits including the reverse bleeder pump and a ton of accessories and I have been using it for many years. I swear by this system after spending years working on all sorts of machines and this one tool has saved my butt. It turned out to be to be the one tool that could bleed the clutch master cylinder on a GM Pickup truck.

It is simple to use and keep. You just need to clean it after use and store it out of the way but when you need it you will have it. Pushing fluid and air UP the brake lines is a smart way to deal with the air issue. I put a bowl under the master cylinder (just in case) and towels around to catch any drips. Then using a Turkey baster I remove the excess fluid from the master cylinder and into a marked container. As you start pumping the tool it pushes fresh fluid up behind the old so you usually see the difference in the master cylinder reservoir. I like to tap on the calipers first and then the brass blocks used in the brake system with a small mallet and just "tap" and the bubbles break free and head upwards.

We have had this Corvette since summer 1991.

 

I have discussed this issue many times over the last 15+ years. I replaced all 4 OEM calipers in 1985 with SS VBP (out of business now) calipers, NO oring calipers back then, just lip seals. I had 1 caliper leak in the early 90's which I replaced the lip seal with another lip seal from VBP delivered to me free. I have had zero issues with the other 3 calipers plus the rebuilt caliper in almost 40 years! I do change the brake fluid every 3-5 years by just cracking the bleeders until the new fluid appears with a helper pressing on the brake pedal....super easy! I do think many folks with calipers constantly needing attention often are due to either poor caliper quality, failure to periodically replace the brake fluid every several years, and VERY important, proper brake rotor runout.

 

Same here - VB&P from the mid-'80s on my '67. I have used DOT 5 since day one with them and have had zero leaks or issues. Last summer, I finally broke down and flushed the brake fluid - the first since caliper installation - clean and debris free.

The Lone Star calipers I put on my '72 a few summers ago have not been as reliable. I suspect that the leak difficulties seen today are a result of rebuilders just putting in new pistons and seals but not polishing or changing out the SS sleeves whereas our VB&P calipers were virgin SS builds.

 

Did you zero out your rotor runout? O-ring rebuilts might be a bit more tolerant than the original lip seals, but before you waste time doing it again, pick up a runout measuring tool. If you've had your rotors off, there's a good chance that's your issue.

 

It isn't the runout and it isn't the pistons that are leaking. In all cases it is the small o-ring between the caliper halves that is leaking. I had my assistant apply full pressure after bleeding and it leaked then before we even put a wheel on. I'll just try to get new Delco castings with the O-ring upgrade for the pistons and leave the dry side alone. I was just hoping that there is a little known solution like a better type of seal or a machining process that would help that I hadn't seen in my search. Thank you all again.

 

rht69911s

I installed Wilwoods on my 68 back in 2012. I have NOT had a single caliper issue since. I was reluctant to pay for the 4 calipers & Pads + 4 SS hoses but there was a group sale on here..... and I was tired of 15-20 years of leak fixing......over and over.
It was tough to cough up the cost but I am glad I did it now.... it's been over a dozen years and not a single brake issue. If you feel like paying the cost I recommend them.

 

I do my own work because you cant trust anyone now a days to do a decent job. I bought my caliper conversion kit from CSSB inc 4 or 5 years ago (before covid) and I havent had a leak since. You cant just put orings on the lip seal piston and think they will work...https://www.cssbinc.com/corvette-bra...rsion-kit.aspx





The kit comes with new orings to seal the two halves. If thats your only issue you can buy them from CSSBINC

 

I cleaned up the mating surfaces with a metal file for a clean smooth surface, applied a little clean brake fluid to the o ring, bolted both halves together and have had no issues with leaking.

 

Again, LIp seal SS calipers for 40 years now with no issues!

The only real advantage to Wilwoods is that they are aluminum..................IMO

 

I went through the same thing , every 6 months at least one caliper would leak. Until someone on the forum made a suggestion. Every 2 weeks I would go out to the garage and start the vette , move it back and forth a couple times to work the brakes and not have any flat spots on the tires. Never had a leak after that for over 7 years

 

Having to move your wheels so your calipers dont leak is a problem in itself really, not a soution. Thats like putting a new bandaid on a knife wound every few hours instead of getting stitches.
Lip seals ARE the problem

 

I bought new O-ring calipers from Corvette Stainless Steel Brakes, it was not worth the hassle of trying to rebuild 42 year old calipers that would just leak again.

JT

 

The CSSB Inc high-heat O-ring kits are really nice. No leaks from the ones I did, just don't use DOT 5 (silicone), only 3, 4, or 5.1 (glycol)

As for the OP's issue, it seems that once significant corrosion gets into the o-ring pocket between the halves, that caliper is done. Perhaps it could be machined, and a larger O-ring used? You can see the pitting starting in @Rescue Rogers' images above. Fortunately, the O-ring is still working.

The stainless sleeving of our calipers was done to fix the corrosion problem in the bores, It seems that rather than solve the between the halves corrosion, current rebuilders will just warranty out the calipers, or use new castings.