joeveto

My car's brake pedal has grown softer and softer, until now, when it will go all the way to the floor and trip the "brake" light. If I jam the pedal down, it will turn the light off, and the pedal will stay firm for one or two more applications. But then it goes to the floor again. Once at the floor, the brakes grab. But they don't grab as hard, obviously, as they would without this issue.

I don't notice any dripping fluid, and the master cylinder has remained full.

Is this a sign of something else in the brake system needing attention? Or are the calipers not ruled out (as the problem) by the apparent absence of leaking fluid?

Thanks for the advice. I'm sorry if I'm asking a question that's been asked a million times, but a search of the archives brought no help.

Monty

Usually the first signs of a leaky claiper are a wet inner wheel and fluid streaked inner tire sidewall. The brake pads will also be soaked with fluid.

Pete79L82

Your symtoms sound more like a master cylinder going bad than a caliper.

VegasJen

first and biggest thing that I would do is pull all four wheels and inspect very closely the inside of the caliper where the pistons push on the pads. if there is anything that resembles moist dirt or mud or remotely wet, you very likely have bad seals/piston bores in the caliper. you may also notice streeks on the wheels as the fluid drips onto the inside of the rim but it is unlikely you will ever see a spot on the driveway from a leaking caliper unless it is really bad. in any case, just replace them. trying to hone and reseal the original calipers is rarely successful. (if you just have to have your originals, some companies will rebuild yours with stainless steel sleeves for a small additional fee.) other possibilites are worn rotors, too much run out on the rotors and bad flexible lines, although i'm sure there are several other things that could do what your describing these come to mind (i'm basing that on the fact your not loosing any fluid from the master cylinder). if you have too much run out in the rotors, it can cause the pistons and pads to push back into the caliper too far requiring more fluid than a normal pedal stroke will provide to bring them back into contact with the rotor. worn rotors have similar simptoms. very old flexible lines, or lines that have been pinched a few times too many will balloon and expand when pedal pressure is applied. also, it is possible the calipers are sucking air and your getting air in the system but i don't have a lot of experience with this problem. needless to say, all of these are very bad things and should be addressed or you should not drive the car. :chevy

joeveto

Thanks guys. So far, my calipers look really good. That is, no fluid leaks. My lines look brand new. So do you think the master cylinder is the more likely culprit?

67's

If you haven't lost any fluid it is probably the MC, do you have power brakes?

Tom

Brutal64

I went through the same problems as you are describing with my old 68. The pedal would gradually loose pressure, with no apparent loss of fluid from the master cylinder or any leaks from the calipers. It turns out the piston seals in my calipers were bad enough to let air into the system but not let fluid out. I replaced the seals and that solved that problem.

Chris@VetteFinders

I'd replace the MC anyway. Also, could be excessive rotor runout pumping air past the seals.