Help with my Brakes

I need some help getting my brakes on my '99 XJ sorted out. The long and short of the story is, I don't have enough braking power.

I did the rear disc swap last fall from a '96 ZJ. I did not replace the calipers. I swapped in the ZJ proportioning valve. I replaced the rear pads, and had the rotors turned, and they are within spec. I bled everything, and don't seem to have any air in the lines.

Up front, I have a new set of Powerstop slotted rotors, and some new pads, but they are not installed yet. So right now, it has OEM rotors that I had turned and are within spec, and a newer set of pads (less than 2 years).

The pedal has a normal feel to it, solid, right amount of movement, etc, but it just doesn't seem to grab. I do not think I can lock the brakes up.

I was thinking maybe I should replace the rear calipers, but wanted to get some advice on where to start trouble shooting before I start throwing parts at it. Help would be greatly appreciated.

Oh, and I'm on 33's, and have added weight like bumpers, winch, and a boatload of tools.

Obviously going to a different set up would be best. I'm not ready to throw down that on the brakes just yet. I guess I need to clarify that I want to first trouble shoot mine and make sure everything is working properly, before I spend a ton more on brake upgrades.

It's not in panic stops that I am having issues, just normal driving. I was having a tough time in Moab, sliding of of ledges and obstacles a lot faster than I wanted to, mostly because the brakes just weren't holding well.

I know several people that run 33's in both TJ's and XJ's and have no isues like this with the brakes, but no one seems to be able to point me in the right direction.

Did you bleed the entire system when you changed? If you have really old fluid in there, that could be part of the issue.

Watch the fluid reservoir level. Does it have a small leak?

I have crown vic discs on my XJ on 32s and they stop on a dime. I didn't switch out the proportioning valve or anything. I bled the brakes well. I have all new brake hoses too....which could make a difference. Make sure the power booster is working.

Have you looked at the WJ conversion?

http://www.4x4wire.com/jeep/tech/brakes/xj_wjbrakes03/

As I said, I am trying to figure out if what I have is working properly before I start swapping/buying any more parts.

Xj breaks suck. Even the newer stuff. The rear converson won't help the weak front breaks but you can give it more pressure to the rear by cutting a wrap and a half off the proportioning valve spring. Put the uncut side back in toward the valve. All the bleeding and replacing parts in the world won't help overcome the inherant weakness of the crap that came on it.
I think on the newer jeeps the tourqe converter pulls all the time and it makes it hard to stop on a dime from 5mph to 0. I had a bad master cylinder with squishy breaks. Now I have firm pedal but the breaks still suck.

I have a 97 XJ with a 94-98 ZJ rear disc brakes and I swaped in the prop valve too , The brakes sucked with the drums with 33 in mudkings The discs lock up with 34 LTB's . The best upgrade I ever made

Any other suggestions?

Based on all of the other guys that can lock their brakes up with your exact setup, my best guess is air in your system. Glazed pads could decrease performance, but just don't have the stopping power that others do with the same setup.

The cheapest 1st step would be to carefully follow the bleeding sequence (again). I've had good luck with that little MityVac hand vacuum system (ebay for cheap), but there are others that are better. Won't hurt to get some new fluid in there anyway.

If that doesn't fix the problem, another place you may look is the master cylinder. Maybe it's not delivering the pressure you need.

I'm watching this post because I'm just finishing my own disc conversion - waiting on brake hoses. Good luck.

Valvolene makes a new synthetic brake fluid thats suposed to replace or mix with dot 3 or dot 4. Synthetic not silicone dot 5. It's getting easy to find and popular. Has any body used this or could this be a problem?

Well, I started taking everything apart last night, and the only thing I noticed was one of the mounting bolts for the front calipers was seized inside it's sleeve. There also seemed to be some extra fluid in that area, but didn't appear to be leaking.

My plan is I am going to replace all 4 calipers, new pads and rotors up front, and then make sure everything is bled thoroughly.

I'll post the results next week.

Well, after I swapped out 4 new calipers, newer rear pads, new front pads and new front rotors, the braking still sucks. If anything, it's worse than before. Hardly enough grab.

As far as I know, everything was bled correctly. I have a motive power bleeder that works great. Ran through 64 oz of fluid. Right rear, left rear, right front, left front.

SO what's left, booster and master cyclinder?

I really need to get this fixed, and some help would be appreciated.

As I said, I don't think I need to upgrade new WJ knuckles or anything, if I know several people that this set up works fine on.

jdbwrx said:

Well, after I swapped out 4 new calipers, newer rear pads, new front pads and new front rotors, the braking still sucks. If anything, it's worse than before. Hardly enough grab.

As far as I know, everything was bled correctly. I have a motive power bleeder that works great. Ran through 64 oz of fluid. Right rear, left rear, right front, left front.

SO what's left, booster and master cyclinder?

I really need to get this fixed, and some help would be appreciated.

As I said, I don't think I need to upgrade new WJ knuckles or anything, if I know several people that this set up works fine on.

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What pads are you running and what rotors? In the front?

Did you go through the correct bedding in procedure and how many miles have you done since fitting them?

See my site under front brake up grade for the correct bedding in procedure. www.go.jeep-xj.info

How are you hoses? If they are bulging you will be losing pressure when you brake. Just a thought. Hope you get it figured out!!

To answer a few questions:

I was planning on using the PowerStop slotted rotrs, but accidentally bought the cast instead of the composite (oops) so I ended up getting a solid set from PepBoys. They are the ProStop Platinum ($40each).

The front pads are Bendix TitaniuMetallic II Brake Pads. I don't remember what the rears are, but they were the best I could get from PepBoys.

I have not done the bedding in procedure, and I know that will make things better, but the initial grab is not good. I looked up on the Bendix website and plan on using their bed in procedure.

The hoses look fine. I have stainless on both fronts, and the main rear center. The short sections going from the rear hard lines to the calipers appear to be OK.

Can someone remind me what the test is to see if the booster is working properly?

jdbwrx said:

I have not done the bedding in procedure, and I know that will make things better, but the initial grab is not good. I looked up on the Bendix website and plan on using their bed in procedure.

Click to expand...

Initial grab can be almost nil until they are bedded and seasoned and even then depending on the pad, still won't be great or even acceptable.

Can someone remind me what the test is to see if the booster is working properly?

Click to expand...

With the engine off, apply moderate pressure to the brake pedal. While holding pressure with your foot, start the vehicle. The pedal should drop a few to several inches letting you know that the booster is in fact, "boosting".

If you can't hold moderate pressure with the engine running and your foot not sinking to the floorboard, then the master is bypassing internally or you have a leak somewhere.