Did a full brake job and zj disc swap, still not happy with braking power

srmitchell · Dec 19, 2009

I recently did the entire zj rear disk swap on my 01 cherokee.
I used brand new rotors and basic level pads for the rear, and brand new rotors and medium grade pads for the front, all parts from napa. I spent a lot on the brake parts.

I swapped the zj prop valve, bled all 4 wheels, and swapped my front lines to some napa sourced gmc truck lines. (they're longer)

It grabs well, but over all, it's not any better that the factory brake set up.

The front grabs worse than it used to with the old big o tire pads.(from the P.O)

Also, I noticed that they fade hardcore!:flamemad:
The pedal gets mushy, but if I stop and turn it off, the pedal is still firm. Not safe! I can see NO leaks in the lines. And they have been bled properly.

Do napa pads suck? Is there something else I need to bleed in the M.C?

And btw, I know the zj disks don't equal massive braking power, but they feel weaker, especially the new pads and rotors up front.

Im not too happy. Im only on 31's, with some armor, so its not horribly heavy or hard to stop. Thanks!

Frank Z · Dec 19, 2009

sounds like you may have a bad master cylinder or booster.

I couldn't be happier with my ZJ brakes.

FlexdXJ · Dec 19, 2009

Something ain't right there then. Most of the Disc conversion posts i read say that its like night and day. I have a hard time believing that the horrible rear drums grab better than a disc setup.

southernrebel20 · Dec 19, 2009

Could it be that you need to put a few miles on the new pads and rotors to seat the pads properly? I know some pads have a coating on them that needs to wear off before they perform at their best. Just a thought.

DanMan2k06 · Dec 19, 2009

I have a hard time believing that the horrible rear drums grab better than a disc setup.

Then you must not understand the engineering that went into drum brakes

Kidding of course. While drums brakes should way out-stop discs this seems to never be the case. Either way, something doesn't seem right. Could have a bad piston seal in the master cylinder or something of the like.

I know some pads have a coating on them that needs to wear off before they perform at their best. Just a thought.

I feel a lot of people overlook this step, but it IS necessary for your brakes to properly work at full duty. Google "brake burnishing" it and I'm sure you'll get a ton of procedures.

srmitchell · Dec 19, 2009

I've done lots of burnishing. Did quite a few 40 to zero stops, and the pads and rotors are very clean.

I've got about 500 miles on the brakes now, but the power just doesn't seem right.

Fred85 · Dec 19, 2009

did you bleed the prop valve itself?

how many miles are on your booster? they don't last forever...

and finally, bottom level pads are cheapest for a reason...hawk hp pads get recommended a lot on here

srmitchell · Dec 19, 2009

I didn't bleed the prop valve only. I was told that you just have to bleed the air out through the wheels, and there was A LOT tatcame out, and the pedal is firm.

Is there a valve I need to bleed?

Here the pics. The red zj valve, new lines, and rear disks.

Bryan C. · Dec 19, 2009

I did the swap many years ago on my 96. No mods to the prop valve were needed. I noticed an improvement in braking power with mine but nothing like the improvement I got with the WJ conversion on the front.

We recently had someone in the sierra chapter install his ZJ calipers upside down, and could never get them to bleed properly. Are the bleeder ports near the top of the caliper?

srmitchell · Dec 19, 2009

Just checked, they're at the top.

Would it be wise to just replace the whole master cylinder? How hard is it?

Bryan C. · Dec 19, 2009

srmitchell said:
Just checked, they're at the top.

Would it be wise to just replace the whole master cylinder? How hard is it?

I remember reading somewhere that you are supposed to removed the o-ring on the prop valve if your brakes aren't grabbing hard enough?

srmitchell · Dec 19, 2009

Im pretty sure the o ring divides the fluid between front and rear, so if you were to blow a line, all the fluid will go out there, instead of having a redundant, second system.

yetimotronic · Dec 19, 2009

is your cherokee abs equipped? i couldnt really tell from the pics. if equipped with abs maybe the abs pump has some air in it and is causing the issues you described.

joe_peters · Dec 19, 2009

Confusion.

You posted earlier you have a mushy pedal, then later you post the pedal is firm. Mushy pedal yes or no?

Mushy pedal is AIR or bad flexible brake lines expanding.

srmitchell · Dec 19, 2009

No abs.

Let me clarify the mushy-
Motor off- Pedal travels about 1/3rd of the way and stays very firm, as in no leaks.(once the residual vacuum is gone)NOT MUSHY

Driving- The pedal is much softer than before, and it seems to take quite a bit of travel before the brakes grab. SLIGHTLY MUSHY

While driving down the hill near the cliff house in san fran next to ocean beach, the pedal got VERY soft, and braking power got very weak. I pulled over, and looked for leaks, and saw nothing. The pedal traveled very far compared to normal. VERY MUSHY

Thanks for the help guys.

Fastdemise · Dec 19, 2009

When I did the zj conversion I also noticed that the pedal traveled a little farther before the brakes started grabbing but a mushy pedal is air in the system. It's always a good idea to bleed your brakes again. I did it after the install and again a few hundred miles to ensure any air that worked it's way to the calipers was gone. with the engine off you should only have to pump the brake a few times then there should be no give in the pedal. That's my experience hope it helps.

garr · Dec 19, 2009

I did the same swap a couple of months back & it felt the same way, I just could not get it bled out properly the normal way. Now they are great!

First I installed speed bleeders http://www.amazon.com/GOODRIDGE-SPE..._1?ie=UTF8&s=automotive&qid=1261262949&sr=1-1 (Same size front/rear with the ZJ rear disc swap 3/8X24) on all wheels, then I purchased a pressure bleeder & Bled the brakes the right way (Your will also benifet from the fluid change out that happens when you use the pressure bleeder) .
http://www.amazon.com/Motive-Produc..._1?ie=UTF8&s=automotive&qid=1261262505&sr=8-1

And yes you need to bleed the Prop valve first before anything else!
Just hook up the pressure bleeder, Pump it up to 15PSI & open the Prop valve bleeder all the way until all the air is out, Then follow with the rest of the brake system.
After using the speed bleeders & pressure bleeder on the XJ I will never bleed brakes the old way again!

Good Luck.

DanMan2k06 · Dec 20, 2009

Would it be wise to just replace the whole master cylinder? How hard is it?

It's extremely easy. Not too messy either. Took about 15 minutes to get mine off, another 30 to put the new one on and bleed everything.

tomcat · Dec 20, 2009

what order did you bleed the brakes?
should be farthest from the MC fists, working your way to the closest. i usually go back around a second time for good measure

srmitchell · Dec 20, 2009

I bled in the correct order.

Is the bleeder for the prop valve the little hole on the end of the cap?

I guess I just loosen it and then pump?

Did a full brake job and zj disc swap, still not happy with braking power

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