But is it absolutely necessary to replace the proportioning valve guts if you are swapping to disc?

 

I've tried it without the guts and with the guts. With the guts is better.

 

Just changed out my rotors and pads with Powerstop parts and they work great, I paid more for the drilled and slotted rotors.

 

I have a '90 xj with a maddening brake issue. Peddle goes to floor but stops, eventually. Think way ahead. Checked all of the brake lines for leaks or damaged or rusted. All appear to be ok. I have changed: the rear wheel cylinders and brake shoes and adjusted the rears, front pads and calipers, master cylinder (bench blead) and booster. Each procedure was done one at a time followed by vacuum pump bleeding. (hand pump type). Peddle still not high and hard. QUESTION: Is there a way to test the proportioning valve or maybe, at this point, just go ahead and replace it? Fyi. Stock Cherokee. Just bought it so I have no history. I have to get it to stop before I go any farther with upgrades. Any input would be greatly appreciated.

 

WELCOME to CF.
Have you tried bleeding the master cylinder while it's on the vehicle?

 

I have not tried to blead the master on the car. What's your thinking?

 

Many times even though the m/c is bench bled I've had to bleed it on the vehicle also. Of course it's the last place to be bled. If nothing else it eliminates the possible cause of the problem.

 

So bleed the whole system and if that doesn't work bleed the master or bleed the master first then the rest. Can the proportioning valve be tested somehow, or rebuilt?

 

Weeeelllllll...... if you take your bad rear drums to someone who really knows what they're doing you can be VERY suprised the next time you hit the brakes. DAMHIKT.

Of course, you need to do it a lot more often than with disks, which are easier to DIY anyway (unless you have the knack). I'd say that a stock Disk/Drum XJ can stop very well indeed when set up properly but it takes a lot more looking after than an all disk setup. The stock front disks are pretty good but with the rears working properly you've got a much better rig under braking. I don't think that rear disks are required for stopping power so much as reduced maint and ballache.

 

^^^ yep.

 

Bleed the whole system which includes the m/c. Start bleeding from the furthest away from the m/c and work your way back to it. Then bleed it last.

 

Got it. Thanks Any thoughts on rebuilding, testing or replacing the proportioning valve ?

 

I've never had a problem with one. Not much to them.