Brakes won't release...

[dalej]

Just wondering if anyone has had a issue with the park brake not releasing? It has never happened until today... I can not get the truck to roll. It acts like you never push in the park brake. It even sounds different, you know the normal load and unloading of air.... well mine quit sounding like that. The trailer brake seems normal sounding.

Maybe I'll switch the two around and see if it's the valve.

Any thoughts?

 

[NDT]

Read and heed:
http://www.steelsoldiers.com/showthread.php?140345-Air-Brake-Info-and-Troubleshooting

 

[Lmtv772]

Check the three Valves under the driver side cab.
The membrane in them is most likely perished
you can replace with a rebuild kit or get the better shuttle valves instead.
are you losing air pressure when you push the brake pedal?

diaphragm valve as in the LMTV KN25060
Repair kit for diaphragm valve RN11V
or a shuttle type valve as in the MTV KN25061​

 

[Suprman]

Front gladhands need to breathe if they are clogged up your brakes will lock. Behind the front grill is a check valve if this is bad or clogged your brakes will lock.

 

[dalej]

Thanks so much, this is really helpful. I had recently taken off the gladhands in the front and put a 3/8" brass plug in there place. I had made a licence plate bracket and the gladhand covers were in the way. I first will try to move the vented gladhand covers to the rear of the truck.

I really like an understanding of the workings and engineering of these trucks.

I want to remove all of the service and park (emergency) air from the front bumper, is this not a good idea. I just want to have truck/trailer service/emergency. I won't be doing it until I fully understand the pluming of the air system.

 

[dalej]

It's rolling again..... I took out the 3/8" brass plugs and put the female air chucks back in that replaced the gladhands. I had just taken out the air chucks and put the plugs in on Thursday and haven't driven it until I tried yesterday.

Thanks so much for the insight and knowledge on this site.

 

[Lmtv772]

I'm glad you've got it sorted. Yes don't block the gladhands

 

[valkrior]

Thanks so much, this is really helpful. I had recently taken off the gladhands in the front and put a 3/8" brass plug in there place. I had made a licence plate bracket and the gladhand covers were in the way. I first will try to move the vented gladhand covers to the rear of the truck.

I really like an understanding of the workings and engineering of these trucks.

I want to remove all of the service and park (emergency) air from the front bumper, is this not a good idea. I just want to have truck/trailer service/emergency. I won't be doing it until I fully understand the pluming of the air system.

Hey,
I think I might have done the same thing you did. I removed the front glad hands, capped them off with plugs. I drove it like this for months with no issues. I jumped in it today, and it seems like the parking brake is not releasing. Did you just put the glad hands back on the front, and problem solved? Or, was there something special about the front glad hands? I'm pretty sure I threw those old ones away. So, if there is nothing special about them, I'll just get new ones. Thoughts? Thanks, Jason

 

[Ronmar]

Hey,
I think I might have done the same thing you did. I removed the front glad hands, capped them off with plugs. I drove it like this for months with no issues. I jumped in it today, and it seems like the parking brake is not releasing. Did you just put the glad hands back on the front, and problem solved? Or, was there something special about the front glad hands? I'm pretty sure I threw those old ones away. So, if there is nothing special about them, I'll just get new ones. Thoughts? Thanks, Jason

Park brake works in reverse. A capped emer glad-hand can keep you from setting the park brake, not releasing it. You could have a leak or a anti-compounding valve issue. Or a rusted brake shoe…

The proper way to delete the front glad-hands is to bypass/remove the 3 two-way valves under the drivers floor. Look at my utube channel Rronmar, i did a vid, it is fairly easy.