brake pedal popping/stuck?

[freshwhitez]

hey everyone, recently my brake pedal has been acting real weird. It seems like it usually happens at low speeds, but when I go to press the brake pedal in, it feels stuck, and then when I press harder it makes a popping sound and the brakes engage... I don't think it's air in the line, because that would just make it softer and less responsive right? The brakes work fine other than this. hallllllp

[DCaff300ZX]

Not sure if this is the problem as I can't "know" your popping sound, but my very aged stock brakes got to a point where the brake shoes in the caliper would not return to the rest position, and would stay in light contact with the rotor. When I would "pump" the brakes to try and return the shoes to their correct position I would feel a stuck feeling when the pedal was depressed until after a few pumps where at times the shoes would return to place, while other times I would actually have to put my foot under the pedal and lift to return the shoes to position.
The calipers were obviously bad and I replaced them but initially still had the return problem, until I had them adjusted by my Z guy during other service which fixed the problem...I believe it may have been the pedal adjustment in the cabin, but am not sure.
I would check your calipers to be sure they are in spec, and check your brake pedal adjustment to see if that helps.

[freshwhitez]

hmmm. well my brakes have no problem disengaging its only when I start to apply them that it gets stuck and wont press down. And it also seems to happen more frequently near the end of the day, especially if I have been driving most of the day. I thought it might just be the pedal getting stuck on something, sprayed some wd40 up in there, helped for a day or 2, but who knows could've been a coincidence. weirrrrd.

[Ace2cool]

Over the weekend, I helped with Greg's project 240Z, and while we were bleeding the brakes, the rears went fine, but the fronts gave us a lot of trouble. They just weren't filling up the calipers, nor was any air coming out (dry bleed with new calipers and lines), so we disconnected the line at the hard line connect point. I was pressing, and nothing was coming out, but the pedal wasn't going all the way to the floor, so I pressed harder. Heard a pop, and the pedal fell to the floor, and fluid shot into the strut tower. Something black, about 3/4" long, and unidentified shot out and almost killed Greg. After that, brakes bled fine. Just sounds sort of similar to me. I'd suggest flushing the brakes.

[freshwhitez]

thanks for the suggestions guys, I'm gonna bleed them tomorrow and then see what happens from there.

[grk nickafis]

try performing some booster tests and master cylinder tests from the FSM. its on BR8

http://www.300zx-twinturbo.com/cgi-bin/ ... t&total=56

[freshwhitez]

alright, bled the brakes and at first it seemed like it went away. Then later in the day went to take my buddy home and it starts happening again on my way home.

^I will try those tests tomorrow, thanks for the link

Also another thing I don't think I mentioned, it seems like it only happens when I keep the same amount of pressure on the brakes, then when I try to apply more pressure, it gets stuck and then pops. The problem starts after about 10-15 minutes of driving once they get warmed up, then just gradually gets worse and worse until it gets stuck/pops even when I'm not moving and depress the pedal.