Bellow
Hardcore MB Enthusiast
Just sniffing out some ideas here on what is currently an obscure problem.
Working on the front wheel bearings required caliper removal. While I was there I squeezed the piston in and back out again with the pedal a couple of times each side (taking steps to ensure no piston popped out). Left the pistons 'in' for caliper re-fitting but when I went to pump the pedal to seat the pads against the disc the pedal didn't firm up as expected. Eye-balled the pads and calipers and the pads were snugged up to the disc so assumed it must need servo (actually driven from PAS pump) to give me the pedal.
Not so, as on starting it up there is still a long and mushy pedal. Feels like they need bled (but the hydraulics were never broken into and the reservoir level never dropped) which I will do anyway. The other possibility is a damaged master cylinder piston seal but, the brakes work very well (after a test drive that I gave the brakes a decent work-out on) and, when I stand on the pedal although it goes much further that I'm happy with, it still does come to a hydraulic stop - not the floor. That I doubt is possible with a failed master cyl.
Needing bled is the most obvious thought but without breaking the hydraulics, how could air have entered? There are no external leaks or any other untoward signs. Any ideas?
Working on the front wheel bearings required caliper removal. While I was there I squeezed the piston in and back out again with the pedal a couple of times each side (taking steps to ensure no piston popped out). Left the pistons 'in' for caliper re-fitting but when I went to pump the pedal to seat the pads against the disc the pedal didn't firm up as expected. Eye-balled the pads and calipers and the pads were snugged up to the disc so assumed it must need servo (actually driven from PAS pump) to give me the pedal.
Not so, as on starting it up there is still a long and mushy pedal. Feels like they need bled (but the hydraulics were never broken into and the reservoir level never dropped) which I will do anyway. The other possibility is a damaged master cylinder piston seal but, the brakes work very well (after a test drive that I gave the brakes a decent work-out on) and, when I stand on the pedal although it goes much further that I'm happy with, it still does come to a hydraulic stop - not the floor. That I doubt is possible with a failed master cyl.
Needing bled is the most obvious thought but without breaking the hydraulics, how could air have entered? There are no external leaks or any other untoward signs. Any ideas?