Master cylinder pressure switch is leaking
Thread Starter
6th Gear
Joined: Jul 2001
Posts: 6
Likes: 0
From: Great Falls, VA, USA
Master cylinder pressure switch is leaking
My 89 has developed a slight fluid leak through the two pins on the pressure switch. I can watch it bubble out when I press on the brakes hard. It is worse when the air temperature is cold. I've replaced the switch with no success. The switch pins are hollow, so there must be a leak in the proportioning valve or master cylinder piston seals. Should I rebuild the master cylinder and does a rebuild kit include the proportioning valve? I've noted two other posts regarding this problem, but neither seemed to have the cause suggested. Thanks! :confused:
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Master cylinder pressure switch is leaking (jwdarr89)
I don't know why, but I finally stopped my white switch on my brake master from leaking only when I bought a new master from GM and installed it. I went through two rebuilts that leaked.
Le Mans Master
Joined: Jul 1999
Posts: 7,072
Likes: 4
From: Maryland
Re: Master cylinder pressure switch is leaking (jwdarr89)
Where is this pressure switch? Is it on the underside of the cylinder? Mine seems to be leaking from somewhere on the underside & I can find fluid oozing down the booster. :eek: Who does MC rebuilding? ~Juliet
Thread Starter
6th Gear
Joined: Jul 2001
Posts: 6
Likes: 0
From: Great Falls, VA, USA
Re: Master cylinder pressure switch is leaking (Juliet)
Thanks for the help! The pressure switch is the white plastic item on the MC. On the 89, it screws in the top of the MC between the two outlets. Using Google, it appears the combination valve is letting the fluid into switch. It looks like a new MC is the way to go. Anyone have any luck with non GM master cylinders, e.g. Wagner?
