No rear brakes

[Dickinson County Comanche]

While my Comanche was parked over the course of 2 days I almost completely lost my brakes. The rears are worse than the fronts. The fronts will lock up, I'm not sure the rears are working at all. Parking brake also doesn’t work anymore. Any ideas? It must be both rear brakes as it doesn’t pull while braking. The reservoir was low, but not empty and hasn’t lost any fluid since I topped it off. Can’t see any leaks, brake proportional valve is still installed, but is tied up, and is also not leaking. (When I checked initially, it was down, but brake pressure never increased when putting it back up. None of the lines are leaking up to the master, nor is the master. The brake light on the dashboard is illuminated, but will go out if I pump the brakes. I didn’t want to get pads yet, but if I have to I have to. Don’t really want to drive it like this up to the Cars and Coffee meet. Pedal basically goes to the floor and I have maybe 1/2 of decent brakes. Brakes worked like a dream before this.

[Dzimm]

Sounds like you have air in the lines.  Try a good brake bleed and see what it does.

[tugboat95]

That would be the first easy cheap thing to try. You say it was down, could be gotten a gulp of air in the line leading to the rear.

89 Comanche
Eliminator
2wd
4.0L
5 speed PukeGoat
Factory Original

[Pete M]

when you say "up" does that mean the swing arm is at 2 or 3 oclock or straight up vertical?

 

have you bleed the rears using the MJ-specific factory procedure?  Follow the link in my signature to find it.  

[Dickinson County Comanche]

2 hours ago, Pete M said:

when you say "up" does that mean the swing arm is at 2 or 3 oclock or straight up vertical?

 

have you bleed the rears using the MJ-specific factory procedure?  Follow the link in my signature to find it.  

Swing arm straight up vertical. I bled only the rear brakes and my rear brakes returned, couldn’t get the front bleeders loose with my little ratchet. The brakes are manageable now and my light is off, so I’d consider it a success. Hopefully the grass doesn’t die from all the brake fluid on the ground now, and I’ll have to bleed the fronts once I get some time. (And maybe some more leverage)

[Minuit]

The arm connected directly to the valve needs to be horizontal. The arm that bolts to the diff cover needs to be vertical. Otherwise, the rear brakes receive almost no fluid.

[JustEmptyEveryPocket]

For the front bleeders, I would get some PB Blaster on them now, and refresh it every day for at least a week before you try and loosen them again. Crack them off and life gets much worse. 

 

Also, like Minuit said, get your rear valve arm horizontal. Then go through the true bleeding procedure for MJ brakes. They have a funky bypass valve that can easily trap air.

 

Read this thread, including the last comment by Eagle.

 

[gogmorgo]

The valve should be sitting a bit above horizontal, roughly the 2 o’clock position, according to a guy on Facebook who claims to have been on the team that designed the valve.

 

Low fluid without a leak present may mean your pads or shoes are getting close to the end of their useful life. But lots of older vehicles could do with a bleed. It used to be standard to change out the fluid entirely every couple years, but that practice is long gone, and no one pays attention until they start having issues.

Poor rear braking may also just be the brakes are out of adjustment. Self-adjusting drums need harder stops in reverse than most people seem to ever do, so when I get the older fleet trucks in for an oil change I like to find a safe spot in the back of the yard to get up to 10-15mph in reverse and stop a couple times until braking improves.