M931 Brake issue

[D6c]

On my M931 the low air brake buzzer usually goes off after pressure builds up but after braking a few times it comes on again.
The brakes operate normally, but I've found that the spring brake override button won't lock the brakes in either in/out position. The manual parking brake (lever on floor) works normally.

Both air pressure gages register around 125 lbs so it's pumping air like it should.
Any ideas where I should start looking for the problem?

 

[goldneagle]

Spring Brake override does not engage the spring brakes! It releases them. Only time the spring brakes engage is when you put the parking brake on and not override the spring brakes. The also engage when you let all the air out of the system. (at least that is the way it works on the M923.) You may want to read up on the TMs and also how Air brakes work. There are even You tube videos on the subject.

What is the air pressure when the low air buzzer kicks in??

 

[73m819]

On my M931 the low air brake buzzer usually goes off after pressure builds up but after braking a few times it comes on again.
The brakes operate normally, but I've found that the spring brake override button won't lock the brakes in either in/out position. The manual parking brake (lever on floor) works normally.
Both air pressure gages register around 125 lbs so it's pumping air like it should.
Any ideas where I should start looking for the problem?

I think I would READ the -10 if I was you, a LOT of interesting NEED TO KNOW stuff is covered.
Does not lock the brakes, RELEASES the spring brakes, OVERRIDES the brake set incase of a air failure, has it's own airtank,

looks like I am just slow in typing

 

[D6c]

Haven't been around this truck much so I'm not that familiar with it....

So if I understand what the manual says, the spring brake overide button is only used during maint. check of brakes and not like a commercial truck as a park brake. So, does the floor mounted park brake also dump the air on rear brakes to lock them in addition to applying the brake drum on the drive line?....that would seem redundant.

As far as the air pressure... It holds at about 125 psi. Last time I started it the buzzer stopped when it got near to the 125 psi, but after I ran it back and forth a couple of times in the yard the buzzer started again and wouldn't go off. Pressure didn't drop....still held at 125. Brakes seem to operate normally so I'm not sure if it's got a brake problem or a sensor problem.

 

[Suprman]

There are 2 tanks primary and secondary each one has a pressure gauge on the dash and each one has its own sensor tha can sound the low pressure warning. Was everything working fine? Make sure the spring brake override is all the way out. Don't use this control. I believe if this control is not all the way out you can have troube building pressure. Air brakes have springs the engage the brakes. Air keeps the brakes off when you step on the brake pedal it takes the air away and the springs pressure the brakes to stop the vehicle. Pressure up and shut off the truck listen for leaks get windex spray where you hear a leak to find it. With full pressure and truck off have someone step on brake pedal listen for leaks.

 

[Artisan]

A good way to find leaks is to pressurize the system w/ your shop compressor and then listen for leaks w/o the engine running. Yes, be SURE the spring brake override switch is in the NORMAL position. There is another device that diverts air to the main system at about 60-65 PSI. As soon as you get that much pressure the wipers and other items begin to work. Make sure you do not roll till you have full pressure and get tutoring from a pro. I have even seen seasoned pro's DEMAND that the spring break override be hit when you park, NO DO NOT DO THIS, that button is what you use to GIVE air to the brakes for just a few minutes so you can push the truck off a cliff and make way for the other trucks behind you if you break! PS DO NOT LISTEN TO ME! Read the TM's!

 

[sandcobra164]

There are 2 tanks primary and secondary each one has a pressure gauge on the dash and each one has its own sensor tha can sound the low pressure warning. Was everything working fine? Make sure the spring brake override is all the way out. Don't use this control. I believe if this control is not all the way out you can have troube building pressure. Air brakes have springs the engage the brakes. Air keeps the brakes off when you step on the brake pedal it takes the air away and the springs pressure the brakes to stop the vehicle. Pressure up and shut off the truck listen for leaks get windex spray where you hear a leak to find it. With full pressure and truck off have someone step on brake pedal listen for leaks.

http://www.youtube.com/watch?v=ihHYQD9JhfI

I'm too tired to explain, please watch and learn a little.

 

[sandcobra164]

Ooops, should have used this one but watch both to get a good understanding.

http://www.youtube.com/watch?v=wxLXGe_FlwI

 

[RetiredNavy]

The air buzzer should sound when it hits 60 psi. Once it hits the target, the buzzer quits and the compressor builds air until the governor shuts off. At least in my Cascadia it does this.

 

[quickfarms]

What pressure does the buzzer com on at?

 

[D6c]

I do understand how air brakes work...wasn't looking for basic information.
Was just trying to find out how to diagnose the buzzer problem.
I did misuderstand the spring brake overide button since it's not set up like a commercial truck.

The problem isn't that I'm losing air pressure....it stays up around 125 psi.
On start-up the buzzer stops but probably higher than the 60 psi suggested...more like 100.
After using the brake a couple of times the buzzer sounds again and won't stop.....pressures don't drop on either guage. Stays around 125 psi.
Brakes work normally.

 

[Suprman]

Maybe the sensor is bad you can temporarily bypass one at a time to see which one is signaling at the incorrect pressure

 

[trukhead]

http://www.youtube.com/watch?v=ihHYQD9JhfI

I'm too tired to explain, please watch and learn a little.

Ooops, should have used this one but watch both to get a good understanding.

http://www.youtube.com/watch?v=wxLXGe_FlwI

I watched and downloaded both the videos! I now have my fix of air-brake ****.
I can't wait to get my M931A2 down on the farm and play with it!

Thanks for the help with the air-brakes, very informative videos and comments from this thread!!