St Tdci Brakes Will Not Hold Pressure
Posted 03 December 2019 - 04:38 PM
Earlier this year it failed MOT on a rear brake imbalance. The calipers were sticky and the handbrake cables weren't in great condition.
I bought new rear calipers and handbrake cables. Since fitting them I cannot get the brakes bled properly, always sinking.
I've manually bled & pressure bled (1-man job). I thought the master cylinder had reversed a seal so I replaced it and the servo unit, no difference. Handbrake works perfectly tho. When doing an ABS service bleed with ForScan, the OSF actuator was making a loud tinny metallic clicking sound while the other 3 corners were a dull buzz (normal). So I replaced the ABS pump and all sounded good again, brakes bled up fine but quickly began to lose the pedal again. Checked every where for leaks, checked the flexi's, all good.
I parked it up 4 months ago & gave up on it, driving my partners car since then. I've been scratching my head & pickling a lot of people's head's with the issue. I think I might have one last thing to ask for advice on before I give up on it & get rid of it..
I'm now thinking I may have got rear calipers for an estate by mistake. The part number of the current calipers are 4S712552BA/BB & 4S712553BA/BB. As far as I can work out these are in fact for the estate model and the part numbers I should have got are 4S712552AA/AB. They are the same size and shape physically, but would the estate calipers cause the master cylinder/ pedal to have to travel further to apply the brakes causing the brake system to feel & perhaps actually still have air trapped in the lines or calipers and not bleed up correctly. Would this cock-up cause the pedal to require further travel and cause the feeling if air in the lines & constant sinking pedal no matter how much it is bled?
Thanks in advance for any help offered..
Posted 10 December 2019 - 06:25 AM
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