proxlamus© Posted January 24, 2006 Share Posted January 24, 2006 Ok.. a few weeks ago i did my front brakes for the first time.. However, I have bled the brakes and clutch numerous times so I shouldn' t of been a problem.. well after the new pads and rotors, and bleeding the system, I have had some "squishiness".. I went out and bought a vacuum pump hoping it fix the situation.. but here is what I am dealing with : - I jump in the car, start her up and drive to the stop sign about 20 feet away, firm pedal, hard braking - I then drive about 1/4 mile down the street to the next stop sign, the pedal goes about half way down the floor this time and is very soft, so I let up, and push the pedal down again, nice and firm! hmm - I drive about another 1/4 mile to the next stop sign in 3rd gear, push the brakes and it goes about half way again, so I let up and push again, nice and firm!! - I drive to the stop light about 3/8 of a mile away, nice and firm.. argg So the pedal pressure is iffy, sometimes firm and sometimes squishy.. So I have bled the master cylinder 3 times, and I have bled the two front brakes many many many times... 6 times today. The master cylinder has been full of fluid, all the fittings are tight, and the bleed screws are tight.. Here's my procedure : 1. Open up the master cylinder cap 2. Attach the vacuum pump and pump to (-)20 in. 3. Open the bleeder valve about 1/4 of a turn and let it run to (-)15 in. close the bleeder. and pump back up to (-)20in. 4. Repeat numerous times and switch to the other side 5. Keep checking reservoir and make sure it's full I even had my brother pump the brakes 3 times and hold it down, in addition to the vacuum pump!! Any thoughts?? The master cylinder was replaced 2 years ago. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted January 24, 2006 Share Posted January 24, 2006 Have you bled the rears? Maybe the rear shoes are out of adj.? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 24, 2006 Share Posted January 24, 2006 Sounds like the master to me. The way to test a master is with slow steady light pressure on the pedal. If you slam on the brakes or pump the pedal it builds the pressure and the pressure will hold the cup seals tight against the bores. Very light pressure won't. Try that and see what it does. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted January 24, 2006 Share Posted January 24, 2006 So when you replaced the pads what else did you replce. Sounds to me like a master cyclinder is bleeding off pressure or you are getting some pad knock back. Do the pads vibrate when you barley put pressure on them? Have you checked for run out of the rotor? Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted January 24, 2006 Author Share Posted January 24, 2006 Well the rear brakes i didn't touch... I took the car to a shop and they gave me an estimate of $600.. ha.. they said the fronts were gone.. but the rears were in spec.. so I figured I had some time before they pooped out... All I did when I did the brakes, was install new front rotors, wheel bearings, and pads.... and Ive gone though maybe a quart of fluid by now.. flushing it over and over. would adjusting the drums affect it? even though they havent really been touched? the pads do not vibrate or squeel or anything.. and no rubbing.. very little pressure, and I mean little.. still results in a firm pedal.. very firm.. at a stand still once i start moving..it goes down Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted January 24, 2006 Share Posted January 24, 2006 I will bet money it is the master cylinder. I haved owned enough old cars that I have experience exactly what you are saying multiple times. The MC gets a little rust on the inside and/or the rubber cups become brittle, so them getting a seal becomes iffy. That is why stabbing the brakes hard usually works. It forces the cups out into hard contact with the MC walls before any fluid can leak past them, then the pressure that you built up holds them tight. You can bleed the brakes until the cows come home and it won't do you any good. Do you really think air is coming in and out of the brake lines inbetween pumps where the pedal is firm and soft? Quote Link to comment Share on other sites More sharing options...
Mike C Posted January 24, 2006 Share Posted January 24, 2006 Usually when the master goes bad, fluid leaks past the rear. IME, you can remove the master from the booster without disconnecting the lines and check for leakage. And yes, out of adjustment rears on a Z can make the pedal seem mushy and give it increased travel. I have had little trouble with fronts over the years, but rears can be a hassle. I gave up trying to rebuild wheel cylinders and just buy new ones. Calipers rebuild quite well, however. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted January 24, 2006 Author Share Posted January 24, 2006 Ok I lied.. i went back out... and BARELY touched the pedal and pushed very slowly... and it went right to the floor and if I push it hard it's firm... ARGG Quote Link to comment Share on other sites More sharing options...
jonnymrp Posted January 25, 2006 Share Posted January 25, 2006 another important thing is to not hold the bleader open for to long when bleading you have to focus on not letting more fulid out than it can take in or else you will get air in the system. two person bleading i find works most of the time becasue it actually in volves the piston in the master moving like it would. however it sounds to me like you have a problem with you master leaking. check it by ways others have described. hope i have helped jon... Quote Link to comment Share on other sites More sharing options...
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