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73-76 CJ5 Brakes Won't bleed

14K views 22 replies 10 participants last post by  Jcarney1200 
#1 ·
Good evening ladies and gents. Here's my issue. I rebuilt my CJ5 and the last thing to do before taking it out is the brakes. Here's what I've done so far:

1: Tried bleeding them the conventional way (RR, RL, FR, FL)
2: Tried bleeding the front first (FR, FL, RR, RL)
3: Cleaned the proportioning valve

When trying method 1, I didn't have any fluid come out of the rear brakes.
When trying methos 2, I started seeing fluid come out then it disappeared and didn't return.
During method 3, I used air after cleaning the prop valve and each port worked as it should.

Also, when I press the brake pedal, there's about a 1-2 inch gap (play) before it's easy to tell that the master cylinder piston is actuating. It seems like a lot of play to me but I'm niether an expert nor a seasoned vet when it comes to this. I'm just a Nugget so I'm looking for whatever guidance is presented to me.

Having presented my findings, it seems to me the Master Cylinder is bad, however due to cost, I'd like to get the opinion of some pros before I make the decision to replace it.

If it's not and someone has another method of bleeding please let me know.
 
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#3 ·
This^ If you didn't bench bleed the master cylinder before installing that is most likely the problem
 
#4 ·
I've been able to do a quick "bench bleed" while still attached to the truck. I removed the lines, and jammed in a 6" piece of poly tubing into the hole, bench around back into the resoivoir, and pumped a couple times until no bubbles were in the tubing. I forgot the size of the tubing, but poly tubing is dirt cheap at the hardware store. Probobly 1/4"?
 
#6 ·
Greekcj5 said:
Forgive me for saying this but I didn't know the master needs to be bled also. Obviously i have a lot to learn still. I'll try that today and update everyone later. Thanks
Bleed the MC on a bench to get full strokes with the pushrod. The pedal travel doesn't push it all the way to full get the air out when mounted on the jeep.

Also, when bleeding each wheel cylinder, the LR has the longest distance for fluid travel, so I'd bleed it first (assuming your setup of brake lines is stock).
 
#7 ·
Gents, so here's the latest. I removed the MC and bench bled it. Re-installed it, bled the entire system and the brakes will stop the jeep now. However, I have to press the pedal all the way to the floor and only when I get to the very bottom, does it actually start stopping. It feels like the rod that's attached to the pedal is too short and if it were longer the pedal wouldn't have to travel as far to engage the brakes. What are your thoughts?
 
#15 ·
Gents, so here's the latest. I removed the MC and bench bled it.
When bench bleeding, how many times did you press the in the piston? If it was just a few, it could still have air in it. When I did my MC, I think I worked it over 100 times because I didn't want to have to pull it out and re-do it :)
 
#9 ·
One thing I just want to throw out there......does your CJ use a combination proportioning/metering valve? If so, try bleeding the brakes by alternating front/rear as in, FR/RR/FL/RL. I just replaced the brake lines on my 77 and had to do it that way.
 
#10 ·
Thanks moneypit. I'm not sure if there's a metering valve. I can tell the master is not the one for my year set up though. I'm almost flying blind cause the PO had a lot of units replaced and some haven't worked right so far which has led me to make adjustment during the entire rebuild. i drove it for the first time in two years last night and as long as i pressed the pedal all the way down it would stop on a dime.
 
#20 ·
I can tell the master is not the one for my year set up though.
If the master that it has is for front discs it won't have a residual pressure valve built into the output for the front brakes. This valve keeps the springs in the drum from pulling the shoes too far away from the drum. The result would mean that it would require more throw of the master piston to get the shoes to the point where they engage the drum.
 
#11 ·
I'm almost to the same point with mine. I started working on it as a basketcase back in February and I'm hoping to get it on the road for the first time before it gets too cold!

Good luck!
 
#13 ·
I don't know if your CJ has front disk brakes or not, but Ill throw this out there because it's a problem that others have run into. If it does have disks in the front, make sure the calipers are not on backward because this will allow air to be trapped in the system. The bleeder screws need to be the upper side, not the bottom.
 
#17 ·
If you have 4 wheel drum brakes, I suspect they are out of adjustment, all 4 will need to be manually adjusted. Not sure on the jeep, but most vehicles have a knockout in the backing plate that you can insert a brake spoon in to manually set them. Basically, adjust, spin, adjust, spin,repeat until you have the same amount of drag on all the wheels, then hit the brakes a few times and recheck. when all are good, set the parking brake and recheck the rears, adjust as needed.

Contrary to popular belief, just yanking on the parking brake a few times will not set the shoes, and manual adjust has to be done first. After that the parking brake helps to keep it adjusted, the rears anyway.
 
#19 ·
Greekcj5 said:
Lol i don't have a parking brake. I'll check to see if they need to be adjusted though. Thanks
They probably need adjusting. When you get them closer by adjusting through the backing plate, then you fine tune by applying the brakes as you move backwards. The barrel adjusters on these Bendix 11" drums are designed to do that.
 
#21 ·
So here's the latest gents. I actually removed the push rod and using a broken 1/4 inch ratchet extension, measured the lag in the pedal and added an extra 1/4 inch. I cut the extension to the right length to remove the pedal lag and an extra 1/4 inch and welded the extension and push rod together, ground them down and rounded off the end of the extension. Installed it and the brakes work amazingly well now. The pedal is firm, doesn't lag and the brakes catch better than ever before. I think the PO used my rod on his other Jeep and left me with one that barely worked. I'll take a picture of the new push rod in case others have the same issue in the future. Thanks everyone your all your help.
 
#22 ·
So i hope you can see this picture right. My new push rod measures exactly 6 1/8 inches long (no pun intended) and its ground down to the same diameter as the original push rod. I used an arc welder with .030 flux wire set at Max 1 feed speed 5. Hope this helps others.

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