After laying down some rubber I noticed a spongy feel in the brake pedal... I have also noticed some fluid under car recently... I assumed it was power steering fluid but now I'm starting to think it may have been brake fluid...I checked the MC and noticed the rear resevoir was a little low... bleed the lines and added all new fluid. initially I wasn't impressed but after about 15 minutes of "testing" the brakes I felt improvement in the pedal and went on about my business...

Still noticing the fluid leak and spongy feel is back...MC is full and no leaks noticed at the calipers... I am leaning towards replacing the MC and maybe even the powerbooster while I'm at it.

I still have the rubber hoses but already ordered the stainless replacements from Summitt.

I have read that most likely it is air in the lines but after recent bleeding and all new fluid I think it is safe to say it's time to look elsewhere...

Any advice or help would be appreciated.

 

It's very possible with the design of these calipers to introduce air into the system without a visible leak. The caliper pistons have a spring behind them so the pads are in constant contact with the rotor, therefore any rotor runout will cause the piston to move back in forth in its bore just while driving. This rapid back and forth movement of the piston can cause air to be intorduced into the system. I have a right rear caliper that has done this since I owned the car, no leaks, just the pedal gets spongier over about a 6 month period, I bleed that caliper and I'm good for about another 6 months.


Pat Kunz

 

ive got the same problem.. i was thinking about betting new brakes all together.. but after i bleed them and put some new fluid in it felt like the car could stop on a dime! that was about 3 weeks ago.. now they're starting to feel about as sh!ty as they did when i bleed them..

 

I have fought this battle many times and it is always the same result. You have a leak in one of the caliper seals(the one you are finding air in). The leaks are sometimes not very evident and difficult to see. You probably need to replace the caliper with a Stainless sleeved caliper.

 

I bled the brakes and they do feel alot stiffer... I took a close look at the MC and don't see any kind of leak... I am pretty sure it is power steering fluid after all... I did a little looking around and it looks like summitt has the best deal on a new set of calipers w/ s/s sleeved pistons for 479.00 no core charge. the kit is PN SSB A109, It comes with pads , bolts, pad pin, and new hoses and trailing arm lines. best deal for the money. Mid America and year one are quite a bit higher with a 200.00 core charge. SSBC seems to sell a quality product I'll let you guys know how it turns out.

Thanks for all your help.

 

I have been working on vetts for over twenty years. Before any one buys new brakes & possibly have same problem in the near future do the fellowing.Check for leaking off the lower half of the frt calpers. If no dripping & seal areas around the pistons is dry problems is most likely the rear brakes.The second test is go & get some clear hose from ace or a pet store & you will need to bleed the frt & rear calpers inside & outside half.Start with the frt & have some one push down on brake pedal & hod it down. Then open a bleeder. Do not pump the pedal. JUST TAKE ONE PUMP OUT OF EACH BLEEDER. You should see solid fluid come from the bleeder. If you get solid air or air & then fluid oyu have a problem with that calper. THE REAR CALPERS DO NOT LEAK FOR 6 MONTHS TO A YEAR. THEY WILL PULL AIR IN & HOLD AIR FOR SOME TIME BEFORE LEAKING.MOST LIKELY IF THE BRAKE PEDAL GOES HALF WAY DOWM & THEN GETS ROCK HARD THE REAR CALPERS ARE THE PROBLEM.IF THE PEDAL IS SOFT & YOU TAKE A BLEED FROM EACH FRT(LOOKING FOR AIR & PEDAL GETS HARDER YOU WILL NEED TO REBUILD THE FRONTS.The third problem that I have never heard talked about is new rear rotors on the rear Or some one turning the rear rotors. I our shop we never turn the rear rotors. If a 82 or older vette comes in & the rivits are still installed on the rear rotors we do not look for run out.If some one has turned or replaced the rear rotors it means good money for our shop. The rear axles from GM were not turned true from the factory. We have found rear rotors that had as much as 15 thousands run out. Gm rivited the rotors to the axles & turned the axle & rotors as a assembly. If you inspect gm axles you can see where they jiged them up. If you have brake problems check for run out at outer of rotor. Also check for loose axle brgs. If brgs are loose you will never stop having brake problems.If you have more then 10 to twelve thousands run out at edge of rotor you will be rebuilding your rear brake calpers often. My 65 vette & have rebuilt my calpers twice 1982.You may need to replace the rear axles with a set of good after market axle or pull rear axles & have them trued up. Do not ever turn the rear axle brg area to make it a slip fit!!!! We turn all rear axles which have over 5 thousanths. that is because as you move further out from the center of the axle the run out increases greatly. If I can help e mail me at www.fastvette @ISP.com Best of luck. doug In our shop we only replace a few masters a year. It is a good money maker for other shops & for the parts stores.