BeaterShark

Last week, I got in my car to go to work. I noticed that my brake pedal felt a little soft at the firt stop sign. At the second stop sign, I jabbed the brakes good and again it felt soft but it stopped the car well, so I continued on. About 8 miles and 4 stops later, the pedal went all the way to the floor with no resistance and the brakes did little to stop the car.

With the car sitting in my garage, I pumped the brakes a bit to build up some pressure and then held them with a bit of force. The pedal did not leak down and held firm for at least 30 seconds. This confirmed that the master cyl is OK. Also, the fluid level looked good and there were no leaks anywhere.

I have since blead the brakes (with a vacuum pump) and would check the pedal after each. Because they are the easiest, I started with the fronts and bleeding them had no affect on the pedal. Upon bleeding the first rear (driver side) caliper, the pedal firmed up. I went ahead and bled the other rear. I drove the car today and the brakes feel fine.

I've read a lot of posts where it is described that air can get in past the lip seals of a warped rotor or one with excessive runout. When this happens, can you feel the pulsing in the brake pedal? I have none.

Anybody have any other ideas as to what could have happened?

VegasJen

i think there is a point when you can have enough run-out for the calipers to suck air but not enough to make it noticeable on the brake pedal. that would be my guess. another possibility would be the hoses swelling.
it doesn't sound like you were driving hard or fast enough to overheat anything but maybe i'm assuming stuff.
did you have the rear rotors resurfaced by chance? i've heard that the rear rotors are surfaced at the factory as an assembly and they must be surfaced as an assembly in the future to ensure trueness.

BeaterShark

When it happened, I was driving real easy. Heck, the engine had barely warmed up.

The TA assemblies were rebuilt in 2000 by a Corvette shop and I did not have any problems for the first 18k miles. This is actually the only thing on the car I didn't do myself as I was too intimidated at the time.

VegasJen

i wish i had more ideas for you. i was hoping someone else might jump in on this one and help out. the one thing i was going to ask but forgot was, did you notice the air in the fluid on both rear calipers or just one? do you have access to a dial indicator that you can check the run-out? neither of the flexable lines are 'bleeding' are they?

BeaterShark

I used a vacuum pump to bleed the brakes. I could never get a complete seal around the nipple, so I always pull in some air. I just pump out 3-4 oz per bleader to be sure I got all of the air out.

I do have a dial indicator. I have not thought of trying this. I'll do this over the weekend.

How do I check if the lines are "bleeding"? They are at most 3 years old. Now that I've gotten into auto-x, I'll probably replace them all with braided lines, but I'm not ready for that yet.

fontking1a

I had the exact same problem two months ago. It turned out that all I needed was a brake job. New calipers and turn the rotors. My mechanic thought it was the master cylinder so that was replaced first and it seemed to work for about two weeks. But, sure enough, the soft pedal came back and it was indeed.....the front brakes. I would suggest you start there because moe than likely....that's what it is.