4 wheel power disc master cylinder

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wes beem

wes beem

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looking for a master cylinder specifically made for 4 wheel power discs.

Id bought master power disc brake conversion kit for front discs, and im running jeep cherokee rear discs, i didnt realize at the time there were different master cyliinders for disc/drum vs disc/disc application, an oversight on my part, too late to return it so now i need the correct one that doesnt have the pressure valve thing for the rear drums. Online descriptions seem vague at best. Dont wanna make the same mistake twice, so links would be super helpful
 
Since the rear disk dint require the same volume of fluid as fronts a front disk rear drum master will work fine as long as you remove the residual pressure valve from the drum side of the master
 
The only reason they changed the master cylinders for disc brakes was to increase the reservoir capacity to feed the comparatively large pistons (as compared to drum brake cylinders). In the early years with a single pot master cylinder, they simply added an extension spacer between the reservoir and the cap, with later dual pot masters they enlarged the reservoir for the front brakes. They also removed the residual valve from the front brake circuit.
The Jeep Grand Cherokee (not Cherokee- those didn't get rear discs. Two totally different models) rear discs have TINY caliper pistons (as do most all rear discs, since they actually do very little braking) and the volume is nowhere near what is required for the front brakes.
Long story short, a disc/drum master cylinder will work just fine for a disc/disc system as long as you remove the residual valve in the rear brake port.
 
Unfortunately I wasnt successful in removing it. I cant get the brass fitting to come out and im afraid ill ruin it before it ever comes out.
 
Thread a sheet metal screw into the brass seat and pry it out, the residual valve is underneath it, it should just fall out. Then press the brass seat back in and remove the screw.
Assuming it's a Mopar master cylinder, and not one of those kits that uses a Ford or GM master cylinder.
 
You don't need to remove it. Get a nail or other item, sewing needle, etc, about the largest one you can get into the center hole, and simply puncture the rubber
 
Professor Fate said:
Thread a sheet metal screw into the brass seat and pry it out, the residual valve is underneath it, it should just fall out. Then press the brass seat back in and remove the screw.
Assuming it's a Mopar master cylinder, and not one of those kits that uses a Ford or GM master cylinder.
Click to expand...
Came in a PST Kit.

331144069_504127441674881_8019859862648549046_n.jpg
 
That appears to be a Ford master cylinder. Can't tell you anything about their residual valve setup, if any.
 
Imagine that, a Ford master cylinder when I ordered a kit for a 71 Duster. Lesson Learned.

I'm gonna solve this problem come winter. Gutting all this PST stuff and replacing it with a manual brake unit from doctordiff.

Cut all the BS.
 
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