TJ Brake Problem

[cuzican]

I'm not sure if I have a combination of problems or if I'm just missing something.

When I broke my axle shafts last year on my TJ the master cylinder and reservoir went dry on the tow out.

I changed the axle out to an 8.8 with disk brakes. As a part of the swap I removed the O-ring in the proportioning valve. I haven't been able to get a decent peddle since.

A few weeks ago I replaced the master cylinder thinking the problem might be there. No difference. The MC was bench bled twice. The second time when I realized the problem had not disappeared with the new MC.

I have vacuum bled and pressure bled (pump up, hold peddle, release bled screw, tighten bled screw, release brake, repeat) All to no avail. I have front brakes but very mediocre rear brakes.

I have put almost a gallon of brake fluid through trying to flush out any air that could be caught. Not seeing any air at all at the calipers.

Anyone else ever have this happen.

Could the problem be the proportioning valve. has anyone else done an 8.8 disc conversion with the stock proportioning valve with just the O-ring removed.

Thanks in advance

[BrokenAxle]

every 8.8 that i've ever installed, i have left the master and proportioning valve as they were.  with the stock setup i've always achieved a great pedal and awesome braking.

[hps4evr]

i heard a good swap is to go to a prop. valve from a rubicon.  or any jeep wit hfour wheel discs. mayeb a master cyl. as well.

[rws]

If you have front brakes but no rear brakes it is likely to be a problem with the proportioning valve.

[Bnine]

First check is to make sure your bleeders are rightside up. If the bleeders are down, they will trap air, never giving you a half decent pedal.

Prop valves on TJ's are all the same after either 98 or 99. Jeep modifeid their rear drum setup, and put the same prop valve on everything. Drum and disks.

But, I've run 4 wheel disk on 95 prop valves that worked with no problems.

I never pull the o-ring and get a good balance, although lots of people do and that works as well.

First check your system out for air, then maybe try replacing the o-ring agin just to see what it feels like.

Good luck.

[4PLAYZJ]

When I installed the 8.8 in my ZJ I could not get all my air out of the system until I used a vacuum bleeder.  Once I finally got the system bled I found that the rear brakes did not have enough pressure going to them and as a result squeeled,badly, when hot.  I changed my prop valve to one out of a 93-98 ZJ that came with factory 4 wheel disc brakes and it seemed to solve the problem.  However if you have pedal fade I doubt that it is only the prop valve, might be air in the system.  My advise is vacuum bleed the system and then call jeep parts for a new prop valve, they have a whole flock of prop valves that will work and only want about $25.

[cuzican]

Thanks for all the advice I resolved the problem this evening.

Bill was right - I had the calipers on opposite sides. As soon as I switched them and bled the brakes the problem was resolved. They looked fine when I was lying on my back underneath, but as soon as I pulled off the wheels and looked at them from the top I knew I had goofed.  :oops:

Brakes work well without the O-ring in the proportioning valve.

I did find an adjustable proportioning valve for $100 which I may buy if I find the rears are locking up. Would only have to be installed on the rear line.

Also priced a Rubicon valve - new $150

[Bnine]

The free fixes are always the best ones.    

[RckyMtnTJ]

So are the ones we can razz him about!!

[Bnine]

So are the ones we can razz him about!!

     

My buddy Mike bled 2 gallons of brake fluid through upside down calipers for 3 days      He gets his share of razzin for sure..........

Well, that, and he used to have pink pinstrips on his jeep.  :shock:  :shock: