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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
The depth of the master cylinder bore is dimension A to B, A being the bolt face surface at the back of the master cylinder, B being the master cylinder piston cup itself. You can only measure the depth to B from the end of the boss that fits into (overlaps) the brake booster. So the end of the boss is dimension C, and you have to subtract the distance of C to A from the total C to B dimension to get your rod length - to a .02 tolerance. Or you could go get that tool.
Thanks. I installed MC . Tried bleeding brakes with bleeder kit. Thought it would work better but not really getting lots of suction. I did get some liquid through. I got inpatient and tried the old pump brake and hold method again and the brake cylinder'right side as im facing it (rear pass side) rubber came off, and started leaking fluid. Why would this happen? I thought I reassembled brakes just like it was after installing new brake cylinder. Could it be because of the booster rod length issue? Or maybe some kind of adjustment i needed to make when putting it back together? I did go ahead and ordered the tool by the way.
Little hard to follow what you did but if you were trying to bleed the brakes by pressing on the brake pedal and didn't have the drums on you blew the piston out of the cylinder.
Just carefully put it back in, put the drums on, and start over
Yeah, there is probably nothing wrong with your assembly, the brake drum is the only thing that limits the travel of the wheel cylinder pistons. As soon as the first one blew the others just stopped.
Absolutely correct guys..geez. I did not put drum back before starting to pump pedal...
I will start over. So, back to the length of the booster rod question; original rod goes about 3 inches while new one about 2 , maybe 2.5..bottom line, new one is shorter and i am concerned that if rod too short that I will have soft pedal issues or maybe nit even be able to effectively bleed the brakes, let alone habe effective brakes. I have confirmed and I have the 9 inch brake shoes, at least in the back brakes. Should the rod being shorter than original be a n issue? I have used the Max adjustment on that screw that adjusts out or in. I don't know, I just don't think they would sell a booster with such short rod that it would make a difference. Would an inch or so be that vital? I have looked for a booster that specifically states the length of the rod, but none say so. Parts geek and such just says part will fit my vehicle.
I was actually asking if the old rod was the same diameter and thread pitch. Are you afraid you might brake the old booster?
Oh. No, dont appear to be same. I tried screwing the old booster's adjustable screw into new one's, but did not go in after the first turn or so. And yeah, going to definitely need a new booster...; or maybe just a longer adjustable screw , if those are available? See pic. I used the tool and there's about 1/4 inch gap.
I have 1/2 inch drill bit , worn out, and plan cutting smooth round end to length. Then insert a round rubber plug at the end facing inside surface of MC to replicate round tip. I will use it as a plug to shorten the space of the MC depth. Comments..? Think will work??
With brakes being the #1 safety system on the car, and considering all the engineering that went into the system and even the part you're considering to modify, I would also give a resounding NO.
I'm not quite ready to do this project yet, but I pulled out the new AC Delco master cylinder and the A1 cardone rebuilt brake booster and took the measurements. The piston cup is 1" in from the flange face. and the currently un-adjusted booster rod is about a 3/16" shy. What is the depth of the piston in your new master cylider? And what brand is it?
If there is a dimension that is suspect, it would seem to be your master cylinder's. My new one is right at an inch. An old one I have in the corner is also right at an inch. In the first picture I sent (in post #27) with the tool against the back of the master cylinder, you can see the piston is up against the C clip at the rear of the bore. You should be seeing a similar configuration on yours. It seems if you were trying to set your booster rod to an inch you wouldn't be having a problem.
08-13-2023, 04:57 PM
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