So ive been fighting poor braking issues on my XJ since I got it last July.Its a 90 Base Model(No ABS) and was equipped from the factory with 205/75/15 tires. It now sports a 4.5 inch lift with 32x11.50-15 Tires(was like this when I bought it).

The pedal has always been of some concern to me.

Ive inspected the front brakes and they have LOTS of meat left on them.

The rears were about worn out,so I replaced the shoes and at the same time installed new Drums. Im running a D35 so I have the 9 inch brakes in the rear.

Ive pressure bled the system(with the help of my daughter,and later the help of my son), I have gravity bled the system,but I cant seem to get the pedal how its supposed to feel.In town,in traffic it stops ok,but in a panic stop situation from even 35 mph I cant get the brakes to lock up.

Ive even replaced the Master Cylinder with a known good one,bench bled it prior to install.

I can sit at a stop sign and put my foot on the brake pedal,apply pressure,and I get a solid "stop" like its to the floor.Vehicle wont roll forward,but it does creep when I accelerate and have the pedal firmly on the floor as far as it will go.Im not getting an overly "firm" pedal like if the booster has gone bad,I get pedal travel if I put my foot on the brake and then start the vehicle,which as I understand is normal.

Ive adjusted the rears,even though the rears are supposed to be self adjusting.

I will note that my E-brake is not adjusted properly,not sure if that has anything to do with my issue,I just never use the darn thing.

It gets hairy sometimes when im coming down a steep hill,I have my foot plated firmly on the pedal,which is to the floor,and it still wants to creep. So bad that on one of the runs I recently went on,I had another Jeep hook a strap to my tow receiver and ease me down the incline,thats how uncomfortable I felt. If I hadnt been strapped,I feel as though I may have had a "runaway" SCARY STUFF!! The guy who strapped me said the back brakes were engaging,he could see the rears skidding down the hill.

One other thing I might is that there was a a valley between these 2 hills that I am speaking of above,there was no room for anyone else to fit in the valley,so I backed my XJ a little ways up the other side of the hill and shut it off as I waited for the rest of the group to show up. Once we were all ready to climb this hill,I fired up my XJ and panicked,as I had ZERO brakes,No resistance from the pedal at all. I had it in 4lo 1st gear as i eased down to the valley,before starting up the other side,all the while pumping my brakes,I finally got pedal when I got on the level valley floor. Whats up with that? Why would I completely loose pedal if the rear of my vehicle was sitting higher on the hill than the front? Ive checked the fluid and its totally full,I just replaced It with fresh fluid when I swapped the master cylinder.

So what does all this trouble sound like? Hydraulic? Vacuum? Mechanical? Could this be a brake proportioning valve issue? Could it be that the larger rolling mass I have on it now with the tires and wheels,have just rendered my brakes totally inadequate? How can you tell if your Rotors or pads have been glazed,could the front brakes be glazed over causing this issue? Im trying to think of everything I can to fix this problem myself,before I take it to a shop and shell out $$$.

Sorry for being long winded,but I wanted to be as descriptive as possible. Thankis for any and all suggestions and advice!!

 

rebleed the brakes the old fashion way by pumping and holding. start at the farrthest break working toward the closest. check your lines for bulging, if your not using braided lines. after that I might start looking at brake booster/proportiong valve.

 

Ok so I just went and did a test in the alley behind my house.

Heres what I did and the results

Transmission(Auto) in 1st gear,Transfer case in 2HI,Gas pedal engaged,Foot brake to the floor-Results:Back Tires Spin,but no forward movement of vehicle.


Transmission in 1st gear,Tansfer case in 4HI,gas pedal engaged,foot brake to the floor-Results:No forward movement of vehicle.

Transmission in 1st Gear,Transfer case in 4LOW,Gas pedal engaged,foot brake to the floor-Results:Vehicle DID move forward

Results on the last test I can understand,this is expected,correct?

What about the results for the other 2 scenarios? Seem normal as well?

If so,why does my brake pedal feel like it bottoms out?

 

How does the pedal feel when the brakes do finally grab? Hard or soft?

Sounds like you have air in the system or a problem with the master.

I had an issue like this on an 89. I just sold it though. Im pretty sure we had some air in the master but the brakes wouldnt grab until the pedal was almost to the floor. Although they did stop well.

 

x2. dont forget were talking about mid eighties technology/engineering.

 

Def bleed em and make sure that system is absolutely air free

 

cherokee brakes in the early years are very under powered upgrade to dual diag booster and get sme sleep at night.....https://www.cherokeeforum.com/f51/wj...ade-how-13908/

 

I have up graded my front end to H.P. Dana 44 out of a 76 Ford F-150. I know the brake calipers are bigger on the Ford front end than a stock Dana 30, and require more pressure and more brake fluid to stop the 35" tires, and i HAVE NOT up graded the master cylinder, and my front tires will lock up very easy.

So i would say if my stock master cylinder will stop bigger tires with bigger calipers, you are having issues with the mater cylinder. It sounds like to me that the master cylinder is leaking inside internally. Fluid will leak bye the plunger inside of the master cylinder, and back feed back into the resavore.

It sounds like you might have received a bad mater cylinder from the auto parts store, was it a re man or brand new? It would not be the first time somebody has received a bad part from the auto parts store.