Brake problems 97 Grand

[MBBikers]

Recently had the brakes fail on our van, the master cylinder was replaced by a mechanic. We have had some really cold weather lately, so the mechanic wanted to check it again cold, turns out he replaced the M C again (on warranty).Have to take the van back again as the pedal is still very soft with little stopping power. Any suggestions??

[RickMN]

Sounds like he didn't bench bleed the M/C. Or, you've got a leaking brake line. Did he install a rebuilt M/C or new? My experience with rebuilts is so bad I won't install them anymore.