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Here go's, i have a mk5 golf 2.0 TDI i had new disks pads and 1 caliper on the front NS for the MOT, now the whole brake system has been flushed and pressure bled as fluid was brown and pedal was soft after parts chamnged, however the pedal remains soft even after replacement master cylinder and re pressure bled, also if you rest your foot on the pedal with even constant pressure it will creep to the floor with the engine on or off!

Anyone got any bright idea's.

Chris

Shoney
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  • Sometimes bubbles get trapped inside the slave cylinders. I've had to compress the slave cylinders and hold them in with C clamps while bleeding the brakes to get the bubbles out of them. – the_storyteller Aug 01 '19 at 17:46
  • It's normal for brakes to feel a bit spongy until the pads bed in properly, but if the pedal is creeping right to the floor that suggests you have a leak past a seal somewhere in the system, possibly the master or slave cylinder. Maybe some of the "brown gunk" in the fluid has ended up where it shouldn't be and is breaking a seal somewhere. – alephzero Aug 01 '19 at 18:02
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    " if you rest your foot on the pedal with even constant pressure it will creep to the floor with the engine on or off!" The master cylinder is bypassing, replace it with a new one and bleed system again – Moab Aug 01 '19 at 19:58
  • Those sound like answers ;) We have a box for that VVV – Cullub Aug 01 '19 at 20:03
  • I'm down to bleeding the brakes backwards from the slave to the master, there is no signs of leakage anywhere all pipe unions and slave cylinders are dry, while replacing the master cylinder i even checked there was no brake fluid inside the vacuum chamber, this is not spongy due to new pads its something else. – Shoney Aug 02 '19 at 13:23

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A common problem is when Brake fluid is pushed back up into the ABS unit. Carrying solidified goo into the Valves causing the fluid to bypass. Engaging the ABS unit will normally clear the contaminants, Sometime it take a few tries to completely clear it all.

Tom
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  • Sound quiet possible, i have removed the battery and battery box and cracked all the pipes at the abs pump and made sure that no air is coming out and that the fluid is clean, its been bled so many times i'm not sure any more what to do. Do you know if bleeding the brakes with the abs pump powered up would help (ignition turned on) my guess at this point is that valves are stuck in the pump, although i fitted a replacement master cylinder i might need to blow the expence and by a brand new one thats £230 VAG trade ouch.......... – Shoney Aug 06 '19 at 17:22