Working on a 69 250 with power disks.My master cylinder was leaking a lot from the top cover. the brakes work fine just leaking on to the power steering gunk.I tried a new gasket, didnt help. So I went out and bought a new master trying to save time figuering out what was wrong. I put the new one in and same problem I hit the brakes a few time(in the driveway) and its leaking from the top. I tried adjusting the rod from the booster but didnt help. I filled the cylinder to about 1/2" below the top thinking I over filled it. Can anyone point me in the right direction.My head hurts.Thanks.

 

Wow, I have the same truck, and am replacing the master cylinder because mine leaks the same way. Hope to get to it by Tuesday. Hope I don't run into the same issue you are. If you figure it out, please post and let us know.

I don't have a solution for you, except maybe the "new" one is defective as well? I am sure some great answers are on the way!

 

Just took my truck to the local Big O tires. They said try replacing the cap again. Did that. Still leaking from the top.So what do I do now. I took it to the pros and they dont know what to do. I am think of driving of a tall cliff to see if that helps. Gota have brakes. any ideas at all. How full are you guys filling the master?

 

sounds like your breake slave cyl are bleeding back fully after use, a simple 2obl antibleed back will fix this

 

Try exchanging the new master cylinder again. It's possible it's bad still. I put my new one in and it's good. About 17$ from autozone. I have mine full about 1/8" from the top.

 

It is possible to get more than one reman or rebuilt master cylinder that leaks at the top. I keep an old tire tube around for times like this.

I might suggest you get something rubber, (do you still have the old MC) and cut a gasket to place on top of the existing one. It only needs to be at the rim where the top and sides meet.

I was able to stop a leaking MC by doing this a few years back that is still working today.



John

 

I found a brand NEW master and that solved it. $25 more and well worth it. Thanks for all the input