Master cylinder

[DThibault]

My refurbed 91 is back on the road and while driving it this weekend, I had to stop on a hill. With continuous pressure on the brake pedal, I can feel it bleed away from my foot slowly. It will stop well when driving along normally. Is my master cylinder leaking by the piston or is there some other culprit. Thanks, I didnt want to just tear into it.

 

[GHarman]

Possibly the Antilock proportioning valve? Some folks have bypassed that part. I had the same problem on my '91.5.
The '93 has the antilock valve removed from the system! No issues with master cylinder bleeding off with the pedal depressed.
GregH

 

[DThibault]

Thanks for the reply. A while back on this site I saw some hardware fittings posted to eliminate that valve. Do anyone remember that thread?

 

[GHarman]

Do a search in the 1st Gen forum. I remember the thread but don't remember the time frame.
GregH

 

[GHarman]

Did a quick search for Ya, DThibault.
The key term is ABS proportioning valve.
Anyway, here is one link!
Hope it helps?
GregH

https://www.turbodieselregister.com...roportioning-valve?highlight=Remove+ABS+Valve

 

[DThibault]

Thanks, I'll pick up what I need today

 

[RSchwarzli]

Do you have a liquid trail down the bottom center front of the booster? Of what looks like peeling paint?

Most times the master's seal goes, and the fluid starts leaking into the booster slowly destroying it. Keep an eye out for disappearing fluid. It will often build up in the booster before it leaks out.