I really don't get it. Everything new or rebuild. This has happened 3 times now. Bleed the brakes, take it out for a test drive. I get a very solid pedal. Full braking with very little pedal travel and not spongy. NO leaks. Park the car overnight, in the morning, really bad brakes. Pedal all the way to the floor and very spongy. The calipers were rebuilt with lip seals because they don't have SS sleeves. It makes no sense the brakes are just fine all day then in the morning they go to hell. My only thought is bad caliper seals.

 

Search this forum on the topic. There are many posts on how to do it successfully.

 

Do what? Bleeding? Been there, done that.

 

I’ve read through your previous thread on the problem. I can certainly understand your frustration but the only reason you have a mushy pedal is you have air in the system and the only way to get the air out of the system is to bleed it.

There are many posts of people having to bleed, bleed, bleed, then bleed some more to get the last molecule of air out of the system. I have recently read of a guy using a reverse bleeding method.

I won’t go into a rehash of how excessive rotor runout can cause air to be “pumped” into the system from the calipers but know that it happens. In your case, you are saying the brakes go mushy overnight so I don’t suspect rotor runout is contributing to your situation.

Have you considered removing the master and bench bleeding it, then proceeding to bleeding the 4 lines to the calipers? Again, there are many posts on how to do that.

At the end of the day, it is a process of elimination, ensuring each component in the system is functioning as designed, beginning with the highest point in the system and working down.

 

I think I have eliminated the MC and rears from my issue. I get a very solid pedal from bleeding just the fronts. Air comes out as soon as I start bleeding them. If there was still air in the system, I wouldn't have a solid pedal. I don't get why air would get back in the front calipers from just sitting overnight. I can see if I got a mushy pedal after driving it for a while, it could be runout, but that doesn't happen. Also, when I pump the pedal when driving, that doesn't pump up the brakes. I was hoping someone had the same issue and fixed it. I have new rebuild kits coming for the front calipers.

 

All of my calipers had been re-sleeved in the past, and I used O-rings. Once bled, no problems. If you are getting issues the next day, my thoughts are:

• If you are still running non-sleeved calipers, perhaps the bores are not as perfect as you think?
• Have you checked the rotor runout? If they aren't nearly zero, you can end up getting air pumped back into the system while driving.

 

The calipers are non sleeved but in very good shape. Rotor runout is .002. I drove it for about 5 month and didn't have a problem with runout.

 

You do not need sleeves to use o rings. Sleeves are to repair rust damage from water in old brake fluid. If you decide to rebuild again, go to the CSSB INC store on ebay and buy an o ring rebuild kit. The get a pressure bleeder and force the bubbles out. When I first got my car it took 5 or 6 tries bleeding around the car to flush out the old fluid. Water and air. I had the usual lip seal failures then did the oring swap. No leaks and always good brakes

And get rid of any organic brake pads you are using and go semi metallic or ceramic. I use Hawk brand. Very grippy, kind of dusty, but the car will stop very quickly

 

kodpkd,

Aren't you the poster that struggled with brakes all through last spring? Then you became a brake expert in the summer giving advise on how to fix brakes?
Now you are back to square one asking again. So my question to you is, what happened during those stages of repairs? What has changed?
Like they say, always back-track to find original issues.

Myself, I refuse to rebuild Calipers or Masters. Its just not worth the hassle that come back to haunt you later. I would rather pay the extra for professional rebuilt parts with safety in mind. Its something to think about when a kid chases a ball into the street.

I am far from an expert, but have "played" with brakes since the 1960s when asbestos dust would dump everywhere. And back then, we did use the pedal assist.
My suggestions, as others have already said are:

Bench bleed Master. (which you did)
Bleed calipers in proper order. (which you did)
Use pressure tank to bleed entire system, (or vacuum to do just one caliper)
And last but not least. Keep your foot off the pedal until done!

And as a side-note, did you switch to a different fluid? DOT4? DOT5?

 

A brake caliper is the easiest thing to rebuild on our car aside from the ash tray. I'm trying to think of anything that has fewer parts and has nothing to screw up.

 

Yes, I struggled last spring and learned a lot about bleeding the brake system on a corvette. There are a number of things that are unique to the corvette. I have had perfect brakes all summer. This is why I am confident of my bleeding technique. I don't have any problems getting all the air out of the system and getting a very solid pedal. I am using DOT 4 fluid. I checked CSSB's website and they say the O-ring caliper set is for a sleeved caliper. I did switch to semi metallic pads.

 

The tolerances involved with these components (caliper bores, sleeved or unsleeved, seal diameters, material specifications, durometer, etc.) are critical to avoid the issues you are facing. One slight deviation is all it takes.

When you say the calipers “are in very good shape”, what is that opinion based on? Did you hone them? Did you use any abrasives to clean them up? Again, if you altered the diameter even the slightest amount, that could be a contributing factor.

Do you know the manufacturer of the seal kits you bought? There are too many stories about cheap imported parts resulting in problems to mention.

When it comes to brakes, “close enough” doesn’t get a vote. Precision is what is needed.

 

The bores in the calipers do not have any marks, they look new. I didn't mess with them. I'll take a picture of them when I get them apart. I am getting Raybestos WK452 and ACDelco seals. I am not sure of their reputation.

 

Please answer these 2 questions:

Have you replaced your brake hoses? If not, then do it--- I would recommend some of those braided ss hoses, not much more and they're wonderful.
Are you using a pressure bleeder? If not, then buy or make one. I don't even bother bleeding any of my cars since I made mine.

 

Yes SS hoses,,, and yes.

 

Well. I spent probably 10-15 years doing the same thing over and over rebuilding calipers. Every 6 months or so, one or the other, of the 4 would need rebuilding....and mine were sleeved.
I ended up replacing them with Wilwood kit (with SS hoses and whatnot) in 2012 and I haven't had a single issue since. I just got tired and there was group sale on here. It was painful to spend the bucks but in the end it was well worth it. (Just looked at my notes, it was August 2012 so that's 9 years without a single brake issue!)
If I remember right the last straw was following a rebuild and everything feels just fine so I drive off for about a 10 mile round trip exercise..... when I go to get off the freeway the dadgum pedal goes to floor..... that was downright scary.
I could have probably gotten away with some quality rebuilds as recommended on this forum but I just went for it on the group sale. I am glad that I did now. Since you already have new hoses I would probably go get some sleeved rebuilds at Autozone since I gather you don't want to swing for Wilwoods. Lots of folks seem to be ok with the Autozone calipers--- I say Autozone because there is one with walking distance of my place and I buy lots of crap there and quite a few folks have mentioned them on this forum.

 

Wilwoods not out of the question. D8-6 or D8-4?

 

Where have you been for the last several years? I have read dozens of things to go wrong with rebuilding calipers by novice and experts.
Pitted bores, seals that won't hold DOT 3. Pistons get cocked in their bores. The "O' ring between the caliper casting halves leaks and so on and so on.

 

I've been Working my jobs, collecting an earned paycheck, protecting my family and friends, rebuilding my brakes and driving the absolute **** out of my car and living to tell about it.... If you pull a caliper apart and the bores are bad, then you are an idiot for rebuilding it and not replacing it. Sorry I cant help you if you are a Libtard but common sense dictates that if you just bought a NEW remanufactured set and they leak, then its probably prudent that you dont use lipseals again. They arent a very reliable engineered product. They have been around for a long time but so hasnt Biden.
As for seals not holding DOT 3, thats probably and untruth or exaggeration, Pistons getting cocked in their bores can only happen if the brake pad comes out, Oring failure in the casting haves is just poor assembly procedures.


You have 2 caliber haves. a small o ring seal that fits in a shallow machined grove, a set of pistons, seals and Orings for those pistons with return springs. Im sorry if you cant assemble something so simple, maybe stick to the ash tray rebuild

All I see from your posts is that you lash out and belittle posters that are seeking help or offering help. Maybe you should seek employment at he local vehicle registry.
The OP can make decisions for him or her own self without you attacking them....

Heres CSSB incs rebuild instructions....so easy I can do it
http://www.cssbinc.com/images/ads/ho...structions.pdf

 

So,,,,,,,,, I bled just the front left caliper. Lots of bubbles right away, then clear. Now I have a very solid pedal. Drove across town, beer time, sat about an hour, back home, still solid pedal. I will check in the morning again. Somehow I get air in the caliper just sitting, and no leaks.
Is there anything with DOT 3 vs DOT 4? I know DOT 4 has a bit higher temp range.