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Gary, ASE Certified Technician
Category: BMW
Satisfied Customers: 1184
Experience:  Senior Technician
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I just fitted some new pads on my 2004 x5 and now the pedal

Customer Question

Hi I just fitted some new pads on my 2004 x5 and now the pedal seems to creep to the floor there are no apparent leaks is it possible that a rubber in the master cylinder has folded over or could it be something else
Many thanks
Submitted: 2 years ago.
Category: BMW
Expert:  Gary replied 2 years ago.
Hi Mark,
Unfortunately you damaged your master cylinder, by pushing the pedal all the way to floor after your pad change.
The lesson here is when you change pads or rotors, the pedal should only be pumped about 1/3 stroke over many strokes until the pedal is hard. Then you know the pads are all out on the rotors.
Quite common in many cars, the root cause is corrosion within the master cylinder from insufficient brake fluid flushing.
The master cylinder cups get damaged when they travel over this corrosion.
You then end up with a sinking pedal, bypassing fluid internally.
You need to replace the master cylinder.
Customer: replied 2 years ago.
I thought that could be the problem but there are so many possible other
Many thanks
Expert:  Gary replied 2 years ago.
You're welcome Mark.