Has anyone had the seals fail in the master cylinder when compressing piston in brake calipher, The reason I ask is on some vehicles you have to clamp brake pipe and open bleed nipple on calipher BEFORE compressing pison in calipher so as to avoid the problem.

gerry norris said:

Has anyone had the seals fail in the master cylinder when compressing piston in brake calipher, The reason I ask is on some vehicles you have to clamp brake pipe and open bleed nipple on calipher BEFORE compressing pison in calipher so as to avoid the problem.

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It's not something that's commonly reported as an issue, but clamping the flexible hose and opening the bleed nipple before compressing the piston is good practice on any car. Hose clamps are cheap and it takes only a few minutes to set up.

The most contaminated fluid is the fluid at the wheel end of the lines and forcing that back up the system is never a good idea, particularly on cars fitted with ABS.

I thankyou for your input,CertainVauxhall astra models had the problem as I recall from my days in the trade,Clamping brake pipe then releasing bleed nipple is something I always have done, makes pushing the piston back that much easier, Then I gently apply pedal pressure after releasing clamp and tightening bleed nipple Then bleed each side,I have found the "easy Bleed kit" you use off of a spare wheel a great bit of kit.Makes the job that much easier.