I am having problems with our '72 LT-1's brakes. I'll bleed them, and not long after that, the pedal is soft again. I've bled them twice now, and with both times it gets air back in the line. These calipers have only been on the car about two years, with only 5,000 miles or so on them. They did fine up until a few months ago. A close friend and ace Corvette mechanic suggested putting all new calipers that have O-rings on the pistons. Sounds expensive to me. Any suggestions?
Gary

Gary,

I may have a cause for your problem, but like everything else on a Corvette it's gonna cost....
If the rear rotors are able to spin off thier rotating axis, (or wobble) due to worn rear hub bearings or worn shims, they will act as air pumps injecting a reverse pulse into the fluid system Via the brake pads each time they rotate. You will be bleeding the system forever until the rotor problem is fixed. This is a fairly common problem on C3's Check,or have your mechanic check for rotor runout. All this is assuming that the rest of your braking system is sound. Hope this helps you. Good luck!!

C3charlie

I heard that if your wheel bearings are loose you can get air into the brakes the same way. My brakes also got soft earlier this year. When I had her on jack stands I checked for bearing play. The front tires both had some play. Had the bearings repacked and set, rebleed the brakes, and now they have been fine.

Rotor run out ..........................

I know the feeling of failing brakes! I had a proportioning valve go a few years ago at speed. Not fun! All I can say is that I am happy with the O-ring calipers on my car. A set can be had for $400 or less if you look around.

Shortly after getting 'The Toy' 3 years ago the right front caliper locked up and cooked the rotor. The cause was the flexible line. It would let fluid to the caliper but not let it return. Ended up replacing both front rotors (and pads) then.

Last summer the right rear caliper locked up cooking that rotor. After rebuilding all the calipers, replacing both rear rotors (they were too thin to turn), pads, and rebleeding the entire system the pedal has stayed solid. Even over the winter while the car was in storage.

There is an outside chance that there is a pinhole type leak in one of the flexible lines that would only spit fluid when under pressure. But I'd have to agree with the thoughts above about either sloppy bearings or rotor run-out as the cause of your soft pedal, especially if you're not seeing any brake fluid leaking out anywhere.

Hi

Had the same problem .
Aft drivers side caliper kept sucking air.
The rotor run out was minor, but enough for this middle age lip seal piston setup to suck air in.
The problem with the lip seals is that they seal perfectly when applying brake pressure, but when released, due to the piston spring pressing them against the rotors, the brake fluid can not free flow fast enough back, so air gets past the lip seal.
Easy fix. Get the VB&P O-ring kit for about 100 $ and take an afternoon to replace all 4 caliper's 16 each pistons. Leave the piston springs out, they don't do anything anymore as thye O-rings hold the pistons much tighter in the bore than the stupid lip seals.

This worked fine on my car .
O-ring conversion kit , and you can forget about brake problems.

Good luck. Gunther