m923 Reduced power. possibly brake not releasing all way..

[wiersema07]

Ive read like 20 pages of different possiblities of issue. Heres what i got going this morning i went to leave work with truck. My abs light normally comes on after its normally cycle. But always operated normal.. put it in gear and didnt want to move like brakes were stuck i tugged on it all wheels moved .. started going and felt like i was pulling the wheels to go even thou they were moving got on the road and trucks struggling to get up to speed took a mile to get up to 30mph seems to have reduced power.. and wants to slow down when let off gas like brakes are applied alittle.. once i get to 30mph takes another couple of miles and a struggle to get up to 50+ mph. Drove it alittle and stopped to check rear end and smells like hot brakes on rear dual more less on drivers side rear dual and not too much on the passenger side.. turned truck off and let it set few mins re started and tried to get home same thing took forever to get to 30 and didnt want to do much more than that got it faster but took cple miles. Ive read all alot of ABS thread and brakes. But nothing really relavent pertaining to the reduced power. Im guessing its a brake issue thats holding truck back.. none of the wheels are locked up.

 

[Gunzy]

Check the temps on all the rear brakes after a small drive or get the wheels off of the ground and check if they spin free. You will need to chock up well and have air pressure to realease the wedge brakes. If you have one that is excessively hot it is dragging/not releasing. It could be a brake chamber problem or and air supply problem to the wedge brake. I actually had one rear brake get adjusted too tight and start smoking. I was able to back off the adjustment of that one and have been fine since.

 

[ke5eua]

Did you try and push in the spring brake override to rule it out?

 

[wiersema07]

Thanks for response ill look. Thanks for not giving a lecture

 

[wiersema07]

I pushed that spring override in shortly after and light came on but now that its home im going to see if theres air getting to n from it or escaping

 

[ke5eua]

Also another thing to check is the parking brake. There is a roller switch on it and if it gets stuck the spring brake will stay on. Easy way to check is to release the parking brake, ensure the vehicle is chocked, pull the roller back and you should hear a distinct noise in the air intake. Sounds like a goose. If you don't hear that then the switch isn't disengaging and your spring brakes are staying on.

 

[wiersema07]

Copy

 

[M35A2-AZ]

If the spring brake override releases the brakes I would check the roller valve on the parking brake.
Also make sure the front service glad hand has a vent on it and it is clear. When you release the brakes a little air vents out the glad hand.

 

[wiersema07]

Hey guys i just went out to trouble shoot and what i found is on the passenger side rear dual then service brake is applied, it starts to smoke by pad. Im going to pull the cover off by pad to see why its smoking in brakes applied any ideas

 

[ke5eua]

Hey guys i just went out to trouble shoot and what i found is on the passenger side rear dual then service brake is applied, it starts to smoke by pad. Im going to pull the cover off by pad to see why its smoking in brakes applied any ideas

Remember you can cage that individual pack if your stuck somewhere. One out of 5 won't effect your stopping noticeably. Just don't forget about it and never get around to fixing the problem.

Most likely it is set to tight. Caging it will also let you know if its the pack, air to the pack, or to tight.

If its to tight caging it might not help as it is just pulling the spring back just like it should be when driving. Caging it can get the spring further back than normal.

Chock the wheels and release the spring brakes, put the caging bolt in and bring the nut snug, mark it or measure the remaining thread then tighten the rest of the way then measure again. That will let you know the travel in the pack from release.

You can get a static measurement by putting the cage bolt in a pack that is working properly and just finger tight the nut with the spring brakes released. The measurements should be roughly the same between the two at this point. If the pack that isn't working right has less distance from the end if the bolt to the nut then its to tight compared to the one working correctly.

Basically these are ways we used in Iraq and you won't necessarily find them in the manuals. Just take the understanding of how the pack works and coming up with a quick troubleshooting method.

 

[Coffey1]

If you are unaware do NOT take apart any part of the brake system that looks like a can there are springs in there that will kill you.

 

[ke5eua]

If you are unaware do NOT take apart any part of the brake system that looks like a can there are springs in there that will kill you.

I knew I forgot to mention something. I came close to meeting my maker in Iraq pulling a brake pack. Was splitting the pack and loosened the wrong band. Made for a very interesting day.

This is your typical spring pack, there are two bands. Newer packs have a sealed band on the spring side to prevent you from taking it apart. Your truck doesn't have a sealed band.

In short, don't mess with the band closet to the rear, that is a big spring in there.

This is the best image of the inside I could find.

 

[wiersema07]

The sprung ov erride is working as should and the p brake lever is engaging and releasing as should. I took the covers off and watching and its not smoking just some dust on drum when applied brakes. Im guessing that since it got down to 30 degrees it might of been stubborn and not releasing brake all the way bcse it drove just fine not issues now so idk if it was a fluke with cold or is spring or something wasnt lifting the pad all the way up but she ran like a top ill keep an eye on it of it continues ill look into it more i hate to tear it apart with it working at the moment. Thanks for all ur info

 

[ke5eua]

Glad it worked out with minimal tearing into.

Noticed your profile says truck driver. I'd imagine your familiar with the dangers of the spring brakes already.

 

[wiersema07]

Yes so far its working well.. i am familiar with air/spring brakes thats why was hoping i wouldnt have to deal with it there death traps to pple who arent famaliar with em.

 

[wiersema07]

Alright the truck sat over night and looks like when i put in reverse truck will roll when in drive the brakes stick on rear axle if i dont touch the brakes once from R to Nuetral and then go to drive it sometimes rolls.. once i touch service brakes to stop the truck brakes stick and truck wont roll forward.. am i looking at a spring not lifting the pads up or something bigger than that

 

[ke5eua]

Alright the truck sat over night and looks like when i put in reverse truck will roll when in drive the brakes stick on rear axle if i dont touch the brakes once from R to Nuetral and then go to drive it sometimes rolls.. once i touch service brakes to stop the truck brakes stick and truck wont roll forward.. am i looking at a spring not lifting the pads up or something bigger than that

Cage that pack and post results. Need to rule out the spring pack. When you were inspecting yesterday did you notice any minor air leak sounds from the pack. If the diaphragm gets a hole in it it won't operate as it should.

 

[wiersema07]

Yeah the passenger side chamber had air hiss not alot but noticed and heard it. By the top by the rubber plug you can pull out by the screw holes

 

[ke5eua]

Yep sounds like your diaphragm went south and it's not allowing the spring pack to fully disengage. Best bet is to cage the pack until you get a replacement.

 

[wiersema07]

Okay ill have to try that cant say ive ever caged one before.