Can't get front brakes to bleed

[Joe L.]

Re: Can't get front brakes to bleed

Spend the sixty bucks for the Motive pressure bleeder, and never have a problem bleeding Corvette disc brakes again; it takes longer to remove the wheels than it does to bleed the whole system, and 5-10 psi is all it takes.

John-----


I've had one for years but I have not used it as of yet.

[Dallas K.]

Re: Can't get front brakes to bleed

Thanks for all the ideas and support. I'm off to find a power bleeder today.

[Jim T.]

Re: Can't get front brakes to bleed

Dallas you mention bench bleeding the new master cylinder. In my experience with my 68 and 70 when I did it I used the method in the service manual in tilting the master cylinder front down to evacuate all the air. If a master cylinder is bled on the car it is tilted the wrong way. Did you try gravity bleeding the left front caliper at the bleeder valve and disconnecting the brake line from the brake hose to see the gravity flow? Like you I have bled the brakes on my Corvettes doing all the master cylinder rebuilding, rebuilding leaking calipers, replacing calipers, replacing brake hoses and have not encountered any bleeding problems like yours. On my most recent last brake caliper piston seal replacement on both front calipers on my 68 I gravity bled both calipers and did not even use the brake pedal to force the fluid.

[Patrick B.]

Re: Can't get front brakes to bleed

Fluid won't come out of either front bleeder by pumping the brake? This is not a matter of needing a pressure bleeder. If fluid won't come out of the bleeder valve merely from gravity there is an obstruction that must be located.

[Paul J.]

Re: Can't get front brakes to bleed

Larry,

Not only does my wife know how to do the procedure but so do my 17 and now 14 year old. You just have to keep training the other family members.

Patrick

Not just the wife and my four kids, but boyfriends, girlfriends, and all of my older son's friends who stop by the shop looking for him and get drafted into helping out. A couple of neighbors know the procedure too, and that they'll have to work for their beer.

[Dallas K.]

Re: Can't get front brakes to bleed

Well, after many hours of driving around and phone calling, there is not a power bleeder for sale in Wichita, KS. So, I ordered one. But now I have other issues. My calipers are leaking. I think my next move is to get an O-ring upgrade kit and just start over on this project. Thanks for all the help and I'll keep you all posted.

[Joe L.]

Re: Can't get front brakes to bleed

Well, after many hours of driving around and phone calling, there is not a power bleeder for sale in Wichita, KS. So, I ordered one. But now I have other issues. My calipers are leaking. I think my next move is to get an O-ring upgrade kit and just start over on this project. Thanks for all the help and I'll keep you all posted.

Dallas-----


If as you described in your first post you used all new calipers, lines, etc. then I don't understand why the calipers are leaking. The original-type lip seal equipped calipers should not leak when new or when properly rebuilt. You should not have to change to o-ring type to stop caliper leakage.

As far as the power bleeder goes, I didn't think you'd find the Motive Products bleeder at retail outlets.

[Dallas K.]

Re: Can't get front brakes to bleed

Yes, everything new out of the box. Calipers were bought from a vendor at Bloomington show about 6 years ago and sat on the shelf until I installed them a year ago. Now during this bleeding process, I have leaks around the pistons showing up. I'm going to have to repair these, so I'm just going to go to the O-ring style and be done with it. They were done by Lone Star, but I don't expect them to do anything about it now.

[Joe L.]

Re: Can't get front brakes to bleed

Yes, everything new out of the box. Calipers were bought from a vendor at Bloomington show about 6 years ago and sat on the shelf until I installed them a year ago. Now during this bleeding process, I have leaks around the pistons showing up. I'm going to have to repair these, so I'm just going to go to the O-ring style and be done with it. They were done by Lone Star, but I don't expect them to do anything about it now.

Dallas------

Long storage of un-used calipers can cause the problem you describe. In fact, I'm concerned about it myself since I rebuilt my calipers more than 6 years ago and haven't filled the brake system as of yet. So, I may be in for the same problem you have.

Converting to o-ring calipers will require changing both the pistons and the seals. Personally, I'm not convinced that o-ring is the way to go. As I've said before, o-ring disc brake piston technology was available and in use at the time GM designed the 65+ Corvette disc brake system. So, if it's so great, why didn't they use it?

[Larry M.]

Re: Can't get front brakes to bleed

Dallas------

Converting to o-ring calipers will require changing both the pistons and the seals. Personally, I'm not convinced that o-ring is the way to go. As I've said before, o-ring disc brake piston technology was available and in use at the time GM designed the 65+ Corvette disc brake system. So, if it's so great, why didn't they use it?

Joe:

I agree. At one time I thought that o-rings were the best way to go, but after a lot of reading and discussion(s) I am not certain anymore. When I rebuild my calipers in the future I will go back with the original lip seals. Using DOT 5 fluid also helps improve the seal life expectancy.

Larry

[Clem Z.]

Re: Can't get front brakes to bleed

Dallas------

Long storage of un-used calipers can cause the problem you describe. In fact, I'm concerned about it myself since I rebuilt my calipers more than 6 years ago and haven't filled the brake system as of yet. So, I may be in for the same problem you have.

Converting to o-ring calipers will require changing both the pistons and the seals. Personally, I'm not convinced that o-ring is the way to go. As I've said before, o-ring disc brake piston technology was available and in use at the time GM designed the 65+ Corvette disc brake system. So, if it's so great, why didn't they use it?

knowing GM the "O" ring ones cost more and they were not about to spend more $$$ than necessary.

[Bill L.]

Re: Can't get front brakes to bleed

Had the same problem on my 70. Gravity bled and all is well. I had the original MC sleeved and all 4 caliper rebuilt with O-rings so I was in the same boat. Once the fluid started flowing I bled them per the manual and I also pushed out all the dirty fluid until it ran clear.

I agree that GM was likely pinching pennys with the lip seal.


Bill

[Patrick B.]

Re: Can't get front brakes to bleed

Well, after many hours of driving around and phone calling, there is not a power bleeder for sale in Wichita, KS. So, I ordered one. But now I have other issues. My calipers are leaking. I think my next move is to get an O-ring upgrade kit and just start over on this project. Thanks for all the help and I'll keep you all posted.

If fluid is leaking past the pistons but not coming out of the bleeder valves, then the bleeder valves must be obstructed.

[Edward B.]

Re: Can't get front brakes to bleed

Recently had a caliper rebuilt (Porsche, not Corvette) and it came back from a highly regarded shop with a bleeder valve that was not drilled through, hence no fluid flow. Replaced the valve with one of many old ones I have lying around and everything worked perfectly.

[Joe L.]

Re: Can't get front brakes to bleed

knowing GM the "O" ring ones cost more and they were not about to spend more $$$ than necessary.

clem-----

It would seem to me that the lip seal design would be more expensive than o-ring. There's more machining required on the pistons, the seals are more complex and, likely, thus more expensive and pistons springs have to be used with the lip seal but not with the o-ring.