I know this has been talked about over, and over, and over, and over again in this forum. But my question is to prevent me from buying anything I dont need to in order to fix my problem.

I just started to work on my bleeding 2 weeks ago, and after I was done, I found the tell tale stream of fluid on my right rear tire, even though my pedal was rock hard. So I bought a seal repair kit ($4.99) at autozone to rebuild my caliper, since it was already stainless sleeved. That went very smooth (I've done it before with no problems), and once installed again, bled that wheel first, went Ok, and so did the rest of the car, with exception of the M/C, the front part of it bled fine, but the rear part constantly had bubbles. worked for an hour and couldnt remove them (this is the bleedable part of the rear m/c and it is new-2years old). When going back around the car to bleed each wheel again, the right rear bled fine, but when getting to the left rear (the one that I did not rebuild), it produced lots of bubbles also, couldnt get rid of them.

Now I know it isnt the front circuit, since both front wheels and front part of the m/c bled fine with no bubbles. So I am dealing with the rear circuit part of the bleeding job. I ordered another seal kit for rebuilding the left rear caliper tomorrow, thinking that, even though it was not leaking fluid like my right rear, it was maybe sucking air into the worn seals and thus producing bubbles their and at the rear part of M/C. Am I going the right route right now???? By the way, this is a fully restored car with perfect brake lines on it. I did check for leaks and did not find any under the car. Any help is much appreciated guys, thanks!!

Gonzo

 

If the calipers are all original, and are not sleeved with stainless steel sleeves, then the seal rebuild kits are just temporary fixes. You can send your calipers in to have them sleeved, or buy new replacements that are already done. Key here is the stainless steel sleeves. They will not rust and pit like the stock piston bores, and then the new seals will seal a lot better.

 

They are all four stainless sleeved, and it great condition. These lip seals wear more when these cars are stored for the winter and not driven regularly. That was the case with my leaking one on the right rear, when examining it, after tearing into it, it was perfect inside (pistons and sleeves), but one of the seals was leaking. Cleaned it all up and followed the procedures provided by Corvette fever to rebuild the right rear, which worked out great. Like I said before Durango Boy, my problem started after the job was done, and trying to bleed the rear circuit of the brake system. Is it the left rear that might be sucking in air?? thanks for responding!!

Gonzo

 

Hah ha...whoops, got caught reading too fast I guess.


I had a similar problem with air bubbles. Mine were S/S sleeved too so I knew pitted surfaces weren't the problem...yet when I bled I got nothing but air bubbles.

My problem ended up being loose threads around the bleeder valve. When cracked open for bleeding, air was getting in through the threads of the bleeder, and then being pushed back out. It was a never ending cycle.

The fix was easy. I installed a full set of check valve bleeder screws. They have tighter threads to they fit very snug, and they also allow for one man bleeding. You can crack them, and nothing will even drip out until you press the pedal and the pressure builds behind the spring loaded check *****.

So not only did it fix the mystery air bubble problem but bleeding my brakes got easier.

Your air bubble problem might not be the same...but the symptom sounds similar.

 

Sorry, I failed to mention that important part, I did order speedbleeders from 'Speedbleeder.com' 6 months ago ,and this wasnt the problem, since they bled fine before doing the work on the right rear caliper. Could it be the left rear caliper, and if it is, why did it just start after my repair to the right rear was done, that is, it bled fine right before doing the work on the right rear, now bubbles all over the place!! thanks again Durango. Maybe you should come up here to Iowa (desmoines) and help fix my problem!!

Gonzo

 

Hello Gonzo,I am kind of new to the forum so please bear with me! As I read your mail my first thought is your seals on the left side to be the probable cause to your problem.The M/C I am sure is good since when you bled the r/s rear you had no air and when bleeding the left side rear and forward you had air again.I think you are right in your thoughts to replace the seals on the left side,air seems to be getting by your seals.And your are SS sleeved so you should be good with the bores.I am the oringinal owner of my 79 and perform preventive maintenance on my brakes on yearly basis.When car was new,replaced the fluid with silicone fluid and replacing seals probably too often too stay ahead of the leaking brake seal issue.Cleaned bores as needed always kept ahead of leak problem.I still do not have SS sleeves but about three years ago while at the Orlando,NCRS show I bought the O ring seal kit from VBP's and for me this was the best thing I have done with my stock brakes.I have not had any leak problems since.Kit included new style of pistons also to accept the O ring seals.I work in aircraft maintenance for a major carrier and O rings are a standard in aviation,miles ahead of lip seals.Later Geno

 

sounds god to me

 

Thanks a bunch Geno, I think your suggestion is valid on the o-rings. Since I am only paying $4.99 for a rebuild kit (includes 4 seals and 4 dust covers), I will try the left rear rebuild this week, if that still does not solve my problem, then I will buy the oring kit with pistons and seals, since my calipers are like brand new. I still wonder why the rear part of the m/c is showing bubbles and the front part bleeds fine. Could this be related to air getting in one of my rear calipers???

Gonzo

 

I'd love to if I had the time, and we'd get it figured out in the end.

 

I'm not that far away, just a little north, and have a wonderful garage that just houses this car, insulated, heated and air conditioned, very clean, and all the tools you would need (and then some). When you get a chance to come up to Des Moines, let me know ahead of time and we can at least just have a beer. Otherwise I will somehow, someway get this problem resolved, even if it means to result to my local chevy dealer who has an old mechanic that works on muscle cars!!

My last question still remains, "would the bubbles in the rear part of the m/c be related to air possibly getting in from the left rear of the car??? I can bleed the front part of the m/c fine, but the rear part (that controls the rear circuit) keeps showing bubbles, like the left rear caliper. thanks

 

I'm no expert but....is it possible the seal on the m/c piston is bad so it's sucking air into the rear circuit? I had that problem last year, bled the system to death, had a great pedal which deteriorated within an hour of driving. When I pulled the cap off the m/c and s-l-o-w-l-y pressed the brake pedal there was air bubbling up in the rear reservoir. Replaced the m/c and all is well.

Just a thought.

 

I suppose it's possible the rear seal in the master is faulty and is pulling air past and introducing it into the system. I have seen more than a few new masters fail.

The problem with air getting in through a caliper, is that the seal would fail both ways, and fluid would come out when you pressed the pedal just like if air is coming in when the pedal returns.

Th pressure of pressing on the pedal is much greater than that of the return, so fluid should come out if it's sucking air in through a bad seal.

 

Thats exactly what is happening to mine, I didnt mention it, but I did notice when looking at the rear part of the M/C that a bubble would come up through the fluid every couple of seconds or so. Did not do this in the front part of the M/C. Man, I hope no fluid got into my power booster!!! I better look at this tonight by unbolting it and moving it out a half inch or so and use a flashlight to look for moisture! Say some prayers for me!!

Gonzo

 

It's very hard to get fluid into the booster.

 

I hope your right Durango!!! I hope your right. Everything is near new in this '68, and I know the booster works good, but that is everyones nightmare!! Those darn things are hell to remove. I did check the vacuum hose and didnt see any moisture in it, so thats a good sign.

Gonzo

 

When the rear seal on that plunger goes out, and fluid actually leaks out of a master, it will generally seep down between the master and the booster. Air can be pulled in before the seal gets so bad that it actually seeps fluid...from what I have seen, but it would leak out before it gets into the booster, and the booster would have to have a bad front seal for it to get in there.

 

Thanks D-Boy, I appreciate it!! I just ordered another M/C from Zip products. It is for $109, but their were none on Ebay (exact reproduction ones) and this one is 100% correct, which I need for my NCRS car. since bubbles come up in the rear part of the m/c, and the pedal goes to the floor when starting the car. good investment even if it does not fix the problem since my current one is 8 yrs old

Gonzo

 

Glad to hear you found a good repro. I would have suggest a rebuild kit for $25, which you can do yourself, but a new one will work fine too and they are easy to replace.

You will remember to bench bleed it right?

 

yes, thanks for the reminder though!!

Gonzo

 

Mine was dry.