This is actually on my E3 and have posted in the E3 section but thought I'd raise it here to reach the wider audience :
Doing my annual brake service today, never had any issues before until today.
I take the outside pad out then restrain one piston with a clamp and pump the other one out with about four full pedal strokes bringing the piston about half way out. I then slowly push the piston fully back with a lever. I then repeat this for the other piston then replace the pad. I then repeat this process on the inside pad therefore ensuring all four pistons are free. Then usually I pump the pedal a couple of times to bring the pads into contact with the disc then repeat on the other side. The problem today is that I now have a very long travel in the pedal and can build it up to about half way with a few quick pumps. Having not disconnected any hydraulics I can't have introduced air into the system, so is this a master cylinder issue ?. It's a RHD car. With the pedal pumped up all four wheels are locked. Can a seal in the master have flipped because of the longer pedal stroke while pumping the pistons out ?. This is a procedure I perform every year but this is the first time I've had this problem. Pedal was perfect before I started doing anything.
I have read several posts on the bleeding process however having not actually introduced any air into the system I'm dubious as to why this has happened. I should also say that the reservoir level never dropped much below max whenn pumping the pistons out, I'm only pumping one piston at a time so not a huge fluid volume being displaced.
Doing my annual brake service today, never had any issues before until today.
I take the outside pad out then restrain one piston with a clamp and pump the other one out with about four full pedal strokes bringing the piston about half way out. I then slowly push the piston fully back with a lever. I then repeat this for the other piston then replace the pad. I then repeat this process on the inside pad therefore ensuring all four pistons are free. Then usually I pump the pedal a couple of times to bring the pads into contact with the disc then repeat on the other side. The problem today is that I now have a very long travel in the pedal and can build it up to about half way with a few quick pumps. Having not disconnected any hydraulics I can't have introduced air into the system, so is this a master cylinder issue ?. It's a RHD car. With the pedal pumped up all four wheels are locked. Can a seal in the master have flipped because of the longer pedal stroke while pumping the pistons out ?. This is a procedure I perform every year but this is the first time I've had this problem. Pedal was perfect before I started doing anything.
I have read several posts on the bleeding process however having not actually introduced any air into the system I'm dubious as to why this has happened. I should also say that the reservoir level never dropped much below max whenn pumping the pistons out, I'm only pumping one piston at a time so not a huge fluid volume being displaced.