soggy brake pedal

Help I recently changed the master cyl on a 3 series because the pedal was sinking I have pressure bled the system 3 times but the problem remains any
ideas??
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Will the pedal sink right down or does it just become good on the second stroke? Cheers Clive
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Clive Turnbull wrote:

Hi Clive the pedal gets better on the second stroke or if you push it fast but it still travels too far thanks T3M
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Have you checked all caliper pistons are free. If not this can give the same symptoms as the working piston tries to push the disc onto the siezed one instad of equal pressure from both sides of the disc. Also make sure the pads are free in the calipers. Cheers Clive
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Hi Clive The local BMW main dealer recently changed the brake fluid on my Gf's car as part of a service, two days later the brake pedal suddenly started dropping to the floor and felt as though the master cylinder had failed. i.e. if you braked hard/fast the pedal would work normally but if you braked slowly you could push the pedal to the floor. I replaced the master cylinder and pressure bled the system but I still get too much pedal travel if I brake softly. I read that the ABS DSC system needs to be active while bleeding so I went out and activated the abs several times then re-bled the system but to no avail I don't think a sticking caliper could be the issue here but I will check them both Thx
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Yes From what you say, I agree. Are the rear brakes drums or discs? If drums is there a chance the shoes are not adjusted up enough? Cheers Clive PS Were the brakes fine before the fluid change? Have heard stories about ABS seal problems when changing fluid.
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Clive Turnbull wrote:

Hi Clive the brakes were absolutly perfect before the DEALER changed the fluid,(they changed it by accident as they had only meant to recommend this) I had replaced the front pads about 3,000km before with no issues. It felt to me like the master cylinder had failed that's why I replaced it (an expensive guess it appears) I am waiting till I can get this car on a ramp to check out all of the brakes at once. Is there a procedure for bleeding the ABS system without the BMW service tool to tell the ABS valves to open? Once again many thanks for your help T3M
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Hi Have you tried this manual bleed. 1) Obtain an assistant and bleed tube and bottle with some fluid in. 2) Start with the N/S rear.Tell assistant to pump the pedal till it is solid and keep pressure on pedal, with tube and bottle attached slack off bleed screw GENTLY till the assistant feels the pedal fall away. Lock up bleed screw and tell assistant to release pedal. Repeat this procedure till pure fluid comes into the bottle. 3) Do this on all wheels working to nearest to master cylinder last. Do this with engine idling. Be CAREFUL and WATCH YOUR EYES this high pressure fluid and if the tube come off it can be dangerous. This is not the recommended way of bleeding brakes but it has got me pedal pressure back when all else has failed. Good luck Cheers Clive
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