Spongy Brake Pedal 67 Camaro

[j1m68]

I have to bleed my four piston calipers every two months to burp the air out of them. There is no evidence of brake fluid leaking anywhere. They were stainless steel sleeved 20 years ago and built with the factory style lip seals. Ten years ago I rebuilt them with the O ring kits because they were leaking due to lack of continuous use. Didn't have a problem until 3 years ago when air was getting into them and I had to bleed every few months. I rebuild the calipers again last year and rebuilt the master cylinder this year(that was sleeved 25 years ago). I had the rotors turned so I know those are good. I also have a 68 Camaro with the same factory calipers and O rings installed in those and the brakes are perfect. When I rebuilt the calipers last year the sleeves did have some shiny areas on them. Is it possible that the sleeves are compromised and possibly worn where I should get them replaced with new sleeves. So frustrating to have to bleed my front calipers every 2 months.
Any advise would be appreciated. Jim

[1967 4K]

I replaced my 67 disc brake MC back mid summer and had hard time bleeding my front four piston calipers. Was advised that in most cases depressing the little button on the back side of the round device ( sorry don’t know proper name of it) that is first downstream from MC wasn’t necessary.
I remembered depressing it years ago when first putting brakes on the car in 1995. I made me a small wooden wedge cut from a 2x4 and pushed it between the button and the booster.
Debbie n I went through the process and everything changed. Got good solid fluid flow and the pedal felt as it should IMO.
I’ll enclose a pic of the round device and my wooden wedge. Bleeding brakes can be a pain sometimes and I was getting frustrated till I did this.

[j1m68]

Hey Richard. That's the metering valve. I also made a wedge and was able to bleed all four wheels successfully. But two months later i get a spongy pedal again.

[1967 4K]

Hmmm, you may have MC issues not caliper. Call Mike Gibbons n ask him about your situation. Very knowledgeable brake guy.