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No Parking Brakes 1997 M1078

Oxyacetylene

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When I first got my truck I temporarily capped the front emergency glad hand. It's bad I know, but my parking brakes still worked just fine. Maybe that's because of a leak I had somewhere else, who knows. I fixed the two way check valve causing that leak and uncapped it. The parking brakes require air pressure to RELEASE them. If you have parking brakes with all air drained out of the system then like others said you are getting pressure fed to them somehow. If that is the case then worst case scenario you could start by tracing that air line to see where it is hooked up and see if it is hooked up wrong somewhere. It should be the outer line hooked to the brake cans. This line is where the air comes into the can to push the diaphragm and spring outwards and release the parking brake. The middle line is the pressure line for applying the service brakes, and the innermost line is the vent line.

edit: I'll also add that since it has been a day or two then likely all the air is now drained out of the system. Take the rubber plug off the rear of the brake can (if one is there) and look inside with a flashlight. You can tell if the spring is compressed or not. When you cage the brakes you are essentially doing the same thing as applying air pressure; it pushes the spring outwards to compress it. The cage bolts engage that spring and pull it out mechanically instead of using air pressure.

2nd edit: I had the line assignments wrong above so I corrected it.
 
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autolocators

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Ok guys just got done driving my truck for the first time. Unfortunately it's not good news. These knuckleheads said they fixed everything. They obviously don't know what they are doing. My parking brakes still are not working. I tried draining all the air and truck is still hard to move. With normal air pressure front and rear when you engage parking brake a very small amount of air comes out of blue glad hand. See pics I'm at a loss. I could not make it more than 5 miles as I realized the rear brakes were dragging building up heat. In fear of catching on fire or hurting something I pulled over and parked at another shop. See pics of rear cans pads and I even took a video of the park brake lever operation it just doesn't seem right the way the park air is engaging

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Ok guys just got done driving my truck for the first time. Unfortunately it's not good news. These knuckleheads said they fixed everything. They obviously don't know what they are doing. My parking brakes still are not working. I tried draining all the air and truck is still hard to move. With normal air pressure front and rear when you engage parking brake a very small amount of air comes out of blue glad hand. See pics I'm at a loss. I could not make it more than 5 miles as I realized the rear brakes were dragging building up heat. In fear of catching on fire or hurting something I pulled over and parked at another shop. See pics of rear cans pads and I even took a video of the park brake lever operation it just doesn't seem right the way the park air is engaging

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So now the issue it's the parking brakes are not releasing? I thought they were not engaging before? Maybe I got lost somewhere?

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autolocators

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So now the issue it's the parking brakes are not releasing? I thought they were not engaging before? Maybe I got lost somewhere?

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Diesel you are correct I think it may be both. Parking brakes not engaging and rear shoes are stuck. They are not stuck so bad the truck wont move they are obviously dragging. I'm learning these systems and wonder if that air valve in front behind bumper has anything to do with these issues.

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snowtrac nome

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first off don't take it back to that shop they know nothing about air brake systems. secondly if air is coming out of the blue gladhand you have a bad check valve in the set of 4 behind the step. the blue glad hand will have a vent on it, if the vent isn't present the system will keep your brakes locked until you remove the gladhand and vent it. it sounds like you may have multiple issues related to incompetence you will have to work through. next time you pay some one to work on your brakes ask to see their airbrake card. if they don't have it go else where they might get you or someone else killed.
 
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You shouldn't have any air coming out of the front BLUE glad hand at any time. That is service brake air in from a towing unit. When the parking breaks are set there should be air coming from the red one for a sudden release. If that one is constantly​leaking then that is the check valve.
Edit: sorry wasn't paying attention to my Grammer on my phone. It's brakes.
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NDT

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Some advice. Don't take your FMTV to any shop period. Learn the systems and fix your truck yourself. The hive here has figured out nearly every issue and posted solutions and can assist you. HOWEVER, to assist you, you will need to report back precise symptomatic information.
 

autolocators

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Some advice. Don't take your FMTV to any shop period. Learn the systems and fix your truck yourself. The hive here has figured out nearly every issue and posted solutions and can assist you. HOWEVER, to assist you, you will need to report back precise symptomatic information.
NDT thanks for intel. Im having truck towed back to my shop I never usually let people work on my things but figured that this may have been over our head. Now I see I can't trust anyone but myself. I will get the truck back and then I can succinctly document what is and isn't working and what it is doing in a timely matter.
 

autolocators

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Ok we spent some time at my shop messing with my truck. It appears that right rear forward brake chamber is leaking air. You can hear it bleeding out with park brake enabled. Also some genius appears to have broken the key on the inside of the brake chamber probably in an attempt to release the brake but now it's going to be hard to take them apart. Any suggestions?

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NDT

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Replace the leaking unit and the unit with the broken off caging bolt. We don't disassemble these due to the strong spring inside.
 

Oxyacetylene

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Replace the leaking unit and the unit with the broken off caging bolt. We don't disassemble these due to the strong spring inside.
Just to add to what NDT said, do NOT try to disassemble the back half of the brake cans. That parking brake spring is no joke. You can buy a whole replacement piggyback unit and just swap that whole section out.
 
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You think I will have any issues with these newer cages since my rig has 2009 front and rear axles.


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They usually go by the vehicle and or they will ask you to send them a picture of the Chambers to match them up. Like I said they are very knowledgeable. I was impressed with their abilities after many failures with other parts distributors.

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doghead

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Please attach photos, not link them.

I told you how to earlier in this thread.

Use the website help forum if you need help with this.
 

autolocators

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Please attach photos, not link them.

I told you how to earlier in this thread.

Use the website help forum if you need help with this.
Doghead. Thanks for help. Maybe you could elaborate on attaching pictures using tapatalk. It only allows picture link. Obviously a full blown desktop computer version probably will have the options you mention. Please advise.

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doghead

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tapatalk is a phone app.
 
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