cruiser54

There's another hidden issue here.

jshultz78

I wonder if the engine isn't pulling enough vacuum on the booster?

Red1992XJ

Agreed. I am not the most intelligent when it comes to automotive theory, so if I do say something wrong, I apologize. Cruiser, or anybody else, please correct me if I do.

Did you put new rear drums on it? I know you say new everything, but didn't list drums. Are they within spec?

Question, can you pump the pedal to the point where it firms up and can't really be pumped more?

It seems like somewhere you are not able to apply enough pressure, almost as if you can't get all of the air out of the system.

The bleeder screws should be at the top of the caliper so the air will naturally rise when it is bled out, is this still the case on yours. Sometimes when parts are being swapped, things don't always match up as they should.

jpz

Agreed, it shouldn't need brakes from a different vehicle to get it to work correctly. Especially with how many of these are still roaming the streets and stopping at red lights, stop signs, and traffic everywhere.

Before I wasted money on an upgrade I would pull back, punt and start looking at it again (forgetting what work you have already done).

Morat

I wouldn't bother with upgrades to to the front brakes on an XJ before swapping the rears to disks. The system as a whole works great when everything is properly adjusted but those rear drums are always the first thing to need attention. If you ignore them for a few weeks they'll be rubbish again.

jshultz78

The drums were turned. Yes the calipers are on right. Brakes were bled in the right sequence til no air whatsoever came thru. I may try bleeding one more time just to make sure no air had made its way to the calipers or cylinders.

jshultz78

The pedal is very firm, no sponginess at all. It feels 10000% better than it did before I did the dual diaphragm booster, but they just don't hold. The only things I can think of is not enough vacuum, or the booster rod needs to be lenghted just a hair, but I set it to where there's just a little bit of pedal travel before it engages. I may have shortened it a turn or two too much.

dave1123

There may be something everybody seems to have overlooked. When adjusting the rear drum brakes, it's best to turn the star wheel until the brakes are tight enough that you can't turn the tire with your hand first. That way the shoes center themselves in the drums. Then back off the star wheel until the brakes just kiss the drums. The brakes on my 2000 XJ work better than the ones on my 2000 WJ if you can believe that. The WJ has ABS and the XJ doesn't. The XJ is running 235/75R15's and the WJ has 245/70R16's in it. Both the same make of tire, but the XJ has a lot less weight.

Red1992XJ

Sometimes when the drums are turned, they take too much material off. Most guys like to do a quick cut and don't measure what they are taking off. Did you measure them when you got them back?

Also, checking that rod length is a good idea.

Dave51

Why not get a hold of a brake pressure testing kit (a gauge and a fitting that goes into the bleeder screw) and see how much pressure you're generating. Discs and drums will be different. Does your MC have a bleeder screw?

Shove some PlayDoh in there and tighten it up. Then you can measure how much play you got.

That's why they call it "Play" Doh.

Waynerd

Just an FYI since it has been mentioned. In 03 the WJ has an upgrade consisting of higher pressure from the master cylinder resulting in a lighter pedal feel. Not sure what what was done but that’s just what I was reading. So maybe 03 and 04 mc’s would be a better choice?

jshultz78

Little update. Pulled the M/C and I seen where I had marked the adjustment nut when I first put it on, it was 1/4 turn in, so I put it back like it was, no change. Got to messing around with the rear brakes, loose as hell. For some reason they won't stay tight. New hardware. So I tightned them up to where I could get maybe 1-1/4 rotation by spinning the tire, took it for a ride, all seems well, checked the temps on the drums, they were about 80 on the passenger side, 110 on the driver. I think I got the driver a hair tighter than the pass side.

Took it to my dirt hill, and it seemed like it was holding going down easier than it was before. Granted I still had to put my foot through the floor but it held steady. It even held backing down, which surprised me, it never did like stopping backing off the 4 post lift at the shop. haha.

One thing I did notice, if I stopped quick in the yard the right front would slide a little but the left front wouldn't. Could this still be a little air in the lines that may have worked its way down? It has a nice firm pedal doesn't feel like any air at all.

cruiser54

Bleed the system again.

Adjust the brakes the way Dave1123 suggests.

aa7kn

I had that same problem with my 91 DJ. Same thing. Normal driving g is fine, but in an emergency if I had to stop fast. No way. What I did was go down to your local junk yard, pick up a fatter brake booster and master calendar from a 1996 DJ or newer. Install it instead of that skinney one that came with the car. It made a world of difference. I can lock em up if I need to, and the brakes are so much more sensitive and responsive. Hope this helps. It's a direct bolt in change, a little fiddly, but it will fit and work good.

Dave51

That won't help if the push rod is a half an inch away. That distance cannot be guessed at. Did you read Cruiser's attachment on adjusting the brake booster rod? Or at least use my suggestion. Put some PlayDoh, Silly Putty, String Caulk, something sticky and with substance on the MC receiving indentation and reattach it to the booster. Take the MC off and measure the thickness of the substance in the receiving cup. The clearance of MC cup to booster rod should be 0.1 - 0.5 mm, which is metric for "practically none".