1980 Cj5 Brake Problems

I purchased a 1980 CJ5 a few months back and have been slowly performing needed maintenance. The brakes were terrible and I had what I call "washing machine" feel in the steering wheel when I applied the brakes. After inspection, I noticed that both front rotors were warped and the rear drums were worn beyond repair. Everything was pretty rusty. The PO mentioned he had problems with the back brakes in the past and had installed a new master cyclinder, although it did not appear new. I have installed new flex lines, new calipers, new rotors, new pads, new drums, new cylinders, new shoes, as well as all new springs/etc. I've manually adjusted the rear brakes and the parking brake is functioning again. I have bled the brakes multiple ways, one wheel at a time, and then one side at a time. Been through this multiple times. I've used a rubber mallet to tap on the cylinders and calipers to dislodge air bubbles. I don't see any leaks and have no fluid on the floor. I have clean fluid coming through with what appears to be no air bubbles. The pedal remains squishy. It has firmed up maybe slightly, but not much. I have no back brakes, when I pull off the drum I do not even see the cylinders move. I have not tried the fronts yet as I still have it up on jack stands in the rear. Any pointers? Any ideas? Is it possible to have a bad master cylinder and still be able to see good fluid flow when bleeding? Does the proportioning valve have anything to do with it? Thanks for any advice. I know bleeding brakes is a pain, but this has me stumped.

 

Welcome From Michigan. I have little or no experience with the AMC Jeeps so I am no help for you, but I know the guys here can help you with your problems. My Jeep is a 64 on a 66 chassis with an F134 motor. Welcome and Good Luck.

 

You get a good flow at the rear lines/bleeder? The block is also a safety device it closes the line that lost pressure when a line fails. It may be stuck to one side. You can push the plunger that lives in the valve back to center. The process is in the factory service manual the lines on the master in the right spot? The front lines hook to the rear port on the master that reservoir should be larger for the calipers

 

Welcome aboard from So. Ga.

 

Thanks for the welcomes. Yes, good flow, and clear fluid to both rear lines/bleeders. No bubbles that I can see. Master is installed correctly, larger reservoir feeds front lines. I've put a little over 32 oz through it. I'll take a look at the proportioning valve. I thought if it were stuck that I wouldn't have any flow to the back, but maybe my idea of flow is actually a trickle. Thanks for the help.

 

Rubber mallet tapping on calipers won’t dislodge the bubbles. Must be a metal hammer to create the vibration needed to dislodge them. Make sure bleeders are at the highest point. Make sure rear brakes are adjusted up correctly or you may never get the air out. If all that is good I’d suspect the master cylinder is either bad or still has air trapped In it (not bench bled before installation) or possibly pressure differential valve/switch (if so equipped). This is sometimes called a combination valve although technically that is just a block with more than one component in it. A pressure differential switch should have a one wire connector coming from it. If you have that then it could be stuck not allowing proper flow or pressure as was said above.
Check all the simple stuff first. Especially brake adjustment.

 

When I converted my 72 to disc's in the front I had a lot of trouble getting the air out. Designers mounted the calipers in such a way that all the air can never come out without having them loose and rotating the bleeders up so they are at the high point.

 

This is a very common problem. My brake bleeders were located on the bottom of the caliper because the PO had installed them on opposite sides. I realized this when i changed out my front axle and installed them in the same orientation.
I tried and tried to bleed them even used a vacuum bleeder and the pedal would just feel spongy i then removed the calipers still keeping the lines intact flipped them upside down while bleeding (keeping the bleeder at the highest point and problem solved. I did end up switching the calipers to the correct sides once i found that this was the problem them to avoid this problem in the feature

It take only a few min to remove the bolts flip them over and bleed them.

If that doesnt work below is a procedure i use when doing brakes on Cjs

Take off the master cylinder and bench bleed it. After your done bench bleeding i usually plug all the ports and try to push in the piston to make sure there isn't an internal leak in the master if it is hard the master is good.
If you have a brake booster you also want to check the push rod it is a small adjustable screw that pushes on the master cylinder piston this sometimes needs to be adjusted you do not want it to be so far out that it is pushing in the master when you bolt it up but you want to make sure there is about a .020" gap.

Once that is set i bolt up the master cylinder then i hook up the lines to the brass proportioning valve and let fluid to start leaking out the lines before fully tightening them.

Then i bleed all the wheels starting with the rear driver (furthest line from the master), rear pass, pass front and front driver. i use a cheep amazon vacuum bleeder for this.

I have done a lot of brakes on these old CJs they can be frustrating, but stay patient and you will get it figured out. let me know how it all works out.

 

Found a pic of the calipers notice how the bleeder is on the bottom it makes it impossible to get the air out you will see fluid with no bubbles, however all the air is trapped on the upper part of the caliper. Only way to get it out is unbolting the caliper from the axle and bleeding it upside down.(I would strongly suggest to flip the drivers side and passenger side calipers so you wont have this problem ever again