1959 Cadillac Replacement Master Cylinder Leaks

[DylanFan52]

The mechanic working on the brake system on my 1959 Series 62 has installed two master cylinders and they both have leaked.  The cylinders, the first a re-manufactured unit (which we did not plan on getting,) and the second, supposedly a new one with a lifetime warranty both leak in the back where they connect to the booster.  The leak is not coming from the line or the filler cap.  The master cylinders were purchased from one of the "Big Three" national auto part chains.  I have returned those that leaked and have gone with another source.  Just checking to see if anyone else has had the same problem.  The best I can tell my car uses the Bendix model.  The replacements leak  immediately after the brakes are bled.

[savemy67]

Hello DylanFan52,

As lamented elsewhere on this forum, sometimes the quality of replacement parts is just not there.  Has your mechanic considered rebuilding the master cylinder?  Kits are available in the $20 - $40 range.

Christopher Winter

[DylanFan52]

Christopher,   

Thanks for responding.  The rebuild kit may be an option.  The mechanic wanted me to check the forum to see if anybody else has had the same problem.  He is wondering if somehow he is installing it the wrong way and the rod from the booster is puncturing  the seals in the replacement master cylinder.  I have a shop manual and he is following it.  I am hoping that we just received two bad replacements.  He is going to try again Monday with another new master cylinder.  I do not know if there is a way to check for leaks before installing it.  The master cylinder that we replaced was installed five years ago before the restoration started and the car has not been driven since then.  I did put 200 miles on that cylinder without any problems with the brakes but I never checked the master cylinder for leaks since there were no problems and it was never removed from the car.  This makes me wonder if something could be wrong with the booster causing the leaks?