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brake troubleshooting 1985 CJ7

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brake troubleshooting 1985 CJ7
LaJones48

LaJones48

Jeeper
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Location
Monument, CO
Vehicle(s)
'85 CJ7, 258, Howell TBI, DUI ignition, T5, D300, D30, AMC 20 (trussed), Moser 1pc. axles
Happy 4th of July everyone. I haven't been on here in ages, but I recognize some names such as Lumpy Grits.

I've been dealing with overheating brake shoes after replacing everything during a rear axle seal replacement. The drums are too hot to touch after driving 3-5 miles. I've checked the fit of the shoes to the drums, replaced the parking brake cable (all three), bled the brakes several times,blocked the pin on the combo valve as instructed, disconnected the parking brake at the equalizer.

Right now I'm focusing on the wheel cylinders. I have a good brake drum that I cut access holes in so I can watch the brakes operate. The primary link to the wheels cylinder moves, but the secondary doesn't. Is that because there's no self energizing when the axle isn't spinning? The parking brake mechanism works when I pull the cable. The fluid in the M/C moves up and down a little when I have someone press the brakes.

Any thoughts would be very appreciated. I"ll try to clarify anything that doesn't make sense.

Thank you,

Larry
 
:ww::dbanana::banana:
Sounds like the shoes are not releasing.
Did you recently replace the MC or the portioning valve?

LG
 
Thank you for your reply. That indeed seems to be the issue. The M/C has 27K on it. The booster has 22K. The combo valve is original so about 193K. I would like to find a new combo valve. What I have found are not factory though.

Regards,

Larry
 
I would first look at the MC.
You are using DOT3 fluid, correct?
I only buy from NAPA......;)
LG
 
Yes on the Dot3 and the Napa. I just had my wife press the brake pedal and let it return. I see no movement in the fluid. I'm wondering if the compensation valve is clogged. Back to work.

Larry
 
Last edited:
Thanks much. I'm going to do more testing. I'll check back
 
Well I had to take a time out on this project, but I'm back. Does anyone have a reliable source for the proportioning valve? I'm finding plenty of sellers and plenty complaints about quality and/or proper fit. The Jeep part number is 5356622. It has two wires going to the light switch.

Thank,

Larry
 
Just in case anyone is interested, I've gone ahead and had the drums trued up and the shoes arced to match the drums. I finally found a shop in Denver that still does that kind of work. Drivetrain Industries.

Here's my question. I removed the combination valve. The metering rod or whatever it's called was gunked up and the o rings look pretty shot so I ordered up another one. It came with an adapter for the rear port so that will work. The electrical connector is a one wire and my existing one is two, but in looking at the wiring diagram it appears that the unit grounds to the frame and the two wires can both be connected to the one without hurting anything. Am I on track with that?

Thanks for looking. This is the longest my Jeep has been down in 16 years of ownership.

Larry
 
Check with NAPA for your p'valve. Stay away from Crown and Omix brands.
LG
 
I replaced mine when it started to drip about 20 years ago.
Don't recall what the brand name was(Bendix maybe :confused:). Did get it from NAPA.
I'm lucky in that I have a NAPA regional warehouse, about 3 miles from me.
Scary, if Crown is all we have now.............:eek:
LG
 
Crown doesn't show one for my 1985. The one I bought came from Inline Tube, but it has PV-2 stamped on it which Is the same as most others Ive seen advertised.

I mentioned in my last post that the replacement valve has a one wire switch as opposed to the original which has two. From the Jeep wiring diagram it looks like I can just connect the one wire to the two wire because both of the original wires carry 12V when either the parking brake or the pressure differential switch tells it to.

I wish we still had a NAPA. The owner of the NAPA stores around here consolidated all of the smaller stores and we lost a very good one. The remaining one in the Springs appears to be slipping as far as what they carry.

Larry
 
I've gone through the whole brake system on my 1985 CJ7 . Today I bled the brakes again, used the tool to keep the metering valve from popping out, readjusted the shoes after inspecting the brake drum hardware, followed the factory manual for setting the brakes with the self adjusters, checked to see if the brakes are releasing after applying the brakes, and took it for a three mile test drive. When I got back, the driver side drum was about 130 degrees at the hottest point; the passenger side was over 200 degrees by my IR thermometer. I have replaced the combination valve and it isn't leaking or turning on the dash light. So Monday I'm going to call our local Jeep specialist and take it in. I hate to give up, but I'm at my wit's end. Any thoughts on what to check? Thanks to everyone for your help on this project so far.

Larry
 
For the brakes to get hot like that it does sound like they are not releasing. It sounds like the rears only are the issue here. I had an issue once with an older vehicle where one of the front rotors turned blue from not releasing. The problem was the flexible brake line on that side had never been replaced and it had started to come apart from the inside. This caused the fluid to reduce flow after the brakes were released. It does sound like you have that issue with the rear flexible hose.
 
Thank you for the suggestion. I replaced the hoses with stainless ones, but it sure won’t hurt to check the rear one. I’m also thinking of pulling the wheel cylinder in case it’s defective.

Larry
 
I believe I have found the source of my troubles. Today I started by removing the rear drums and checked if the wheel cylinder links moved if I moved the brake shoes. They did. Then I noticed that about a 1/4" of the shoes wasn't wearing toward the backing plate on the right side ( the side that's been getting hot). I checked the other side and it seemed to be wearing properly. I went back and looked at the right side. I pulled on the axle flange and it moved up and down very noticeably. Now I need to talk with the guys who installed my one piece axles for me last fall. Looks like the bearing wasn't installed properly on that side. When I take it off the jack stands the brakes are helping to support the axle. Thus the heat. Gak! Thanks again for all the suggestions.

Larry
 
I will as soon as the problem is resolved.
 
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