Bleeding a height sensing proportioning valve

[RLCollins]

Pete made a statement which to me is a excellent question on my problem, with my 1989 MJ long bed 4.0 I-6 4X4. The early thread was "Brake Height sensing Proportioning Valve Problems" His statement "Bleeding that emergency hydraulic line is a real problem." This is a second line AKA return line that goes back to the proportioning valve by the master cyclinder. So how do you properly bleed a system with a height sensing proportioning valve?

This all started with my back brakes, After inspecting the rear brake shoes, I found there was little to no wear on them. After changing the wheel cyclinders and shoes, I found through the bleeding process that there were no rear brakes, and NO brake fliud pressure on the rear shoes, even after moving the height sensing proportioning valve arm back and forth. This valve was closed to brake fluid flow. So I tried to find a new one, part 52002369 good luck. Well I did find one through Trademotion.com AKA byerschryslerjeep.com. These guys were good, I could not believe they found the part in Denver, Co. I have it in my hand. since my brake system was not working properly I ordered the proportioning valve by the master cyclinder from them also part 52002497, its on its way to me. Their phone number 1-614-238-1631. I hope that it is alright to talk about good suppliers.

Than I looked at the front brakes, the rotors were shot from the truck only having front brakes, since the last owner had the brake job done. After further looking into the brake system the master cyclinder was spongy from day one. So I changed that also. After all these parts being wore out; I came to the conclusion that the remainder of the brake system is also bad. The only part of the system that is worth saving is the metal brake lines, they are not rusted, or leaking brake fluid, so I will keep them.

What should I be looking for in the way of other problems with the brakes? What kind of brakes shoes work the best and last the longest on Jeeps? what about rebuilt calipers? Any experience with which manufactures that last the longest? Are there ones I should stay away from? Are the front wheel bearing serviceable? Can I repack them with new bearing grease? or are the sealed? :dunno:

PS How do you properly bleed the rear brakes with an height sensing porportioning valve in the line? :dunno:

[Eagle]

The second line is not a return line. That has been a common misconception for many years andnobody seems to know where it originated. In fact, it's an emergency bypass line that allows full (unmodulated) braking force to the rear wheels if the front brakes lose pressure.

 

The bleeding procedure as spelled out in the factory service manual has been posted here (I know -- I posted it). I'm at work and don't have time to search for it, but if you search you should find it.

[RLCollins]

OK Eagle

I cannot seem to find it

Could you please help :oops:

I will be completing the brakes today

Need to bleed them :dunno:

[Eagle]

Fourth post in this thread:

 

viewtopic.php?f=2&t=4917&hilit=bleed+height+sensing