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Mondeo ST tdci brakes sinking


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Hey all. My mondeo St tdci 2.2 failed mot on the rear brakes. The calipers were sticking & the handbrake cables weren't in great condition.

I ordered new calipers and new cables. Since fitting them I cannot get the pedal to stop sinking. I've since replaced the master cylinder and vacuum servo & also the ABS unit (abs service bleed revealed a bad actuator or seal in the unit). Still no joy. 

I parked it up & gave up on it for a few months. I've brought back out to figure this out. 100% no leaks. 

Now what I have worked out is that the Calipers I have fitted are in fact for an Estate variant, not Saloon. Apparently the estate calipers are for estates Only. Part numbers are 4S712552BA & 4S712553BA (Estate) & the part numbers for the saloon are 4S712552AB & 4S712553AB.

Does anyone know if this would cause my current problem of the brakes continually sinking? Are the estate calipers internally different and causing the fault? 

There is definitely no air in the system & everything else has been checked and double checked and/or replaced. This has only taken effect since fitting these calipers. 

Thanks in advance for any help offered. 

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  • 2 years later...

That's a weird one I wouldn't ha e thought that wouldnt have mattered as long as they worked ,I'm having the same trouble but I just changed a rear flex cos it was leaking ,going to try forscan bleed 

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The trouble is, if you don't crack open the bleed nipple and clamp the hose before retracting the piston, the fluid is forced back into the master cylinder and apparently 'flips the seals' in the m/c and that causes no end of problems with air in the system. I  experienced this for myself and ended up not only having to replace the m/c - I bought new seals but couldn't get the old ones out - but also had to bleed the abs unit. Good luck! You'll ideally need to have all 4 wheels off before you do the abs bleed as it's an all wheels procedure. (one after the other, not all at the same time) 

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