QuestionQUESTION: We have replaced all pads and rotors and put in new brake fluid and bleed the system twice but the pedal is soft on initial application, but pumps up ok and seems to hold it's place during a stop. We did not have this problem before we changed the pads and rotors. There are no external leaks anywhere we can see. Where do we look now for the solution?
ANSWER: For some reason the pistons are being pushed too far back after the brakes have been used. If you press the brake pedal again after it feels OK (pumped up) does it still feel OK? Try it without the car moving, wait a while and try the brakes again. Do they feel better, or is the problem still the same? If they feel better without the car having been moved, then maybe one of the rotors is warped, or perhaps there is some debris between the rotor and the hub. The rotor then wobbles and pushed the brake pistons back further, which means the first application of the brakes feels spungy since the pistons have to come out further. Unfortunately there is no easy way to fin out which one is causing the problem, but you can have a look at each of the calipers, grab the caliper itself and see which one has the most play. I would check the one with the most play first. Let me know how you get on, Jan
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QUESTION: Thanks for the suggestion, but after you stop and then put the car in park and release the brake pedal, the pedal will be soft in 30 seconds or less. If however you come to a stop and keep constant and even hard pressure on the pedal the pedal does not move. Any other ideas?
AnswerOK, that was a useful test. If you did not have this problem before, and assuming that the master brake cylinder did not mysteriously develop a problem while you replaced the rotors and pads, maybe one of the calipers is not free to move, so that when you apply the brakes it pulls the caliper over, but it stays stressed until you release the brakes and the caliper slowly pushes back. They are called 'floating' but if there is too much grime and rust in the slides, the calipers can stick. Do not apply any lubricant here, but do ensure that the calipers are free to move on the slides. Unfortunatley for you this means removing the wheels again... If you can get to all 4 calipers at once, have somebody apply the brakes while it is up in the air and see if you can spot which caliper is the sticky one... Let me know, Jan
