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Replacing a master cylinder

Last year I bought a pressure bleeder for flushing and replacing brake fluid (well worth the $50).

I’m going to be replacing a master cylinder soon and will use it to bleed the system. I’ve replaced M/Cs many times before and I have always bench bled the cylinder first and then bled the system the old fashioned way.

My question: Is it necessary to bench bleed the cylinder first if I’m using a pressure bleeder? I vaguely recall reading somewhere that it is not, but I’m not sure.


If the master cylinder is properly bench bled and installed no further bleeding is necessary.

No. The master cylinder doesn’t require bench bleeding before it’s installed. That’s one of the advantages of using a pressure bleeder.


What about the air you introduce into the lines when you disconnect them from the old master?

As long as you do not crack open any other bleeders its no problem.

After installing the m/c and connecting the lines you can bleed them and all will be good.