Air brake issues

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superloop

superloop

Member
Joined
Mar 6, 2017
Posts
8
Location
Virginia Beach
Alright everyone,

I am stumped here...

I was driving behind DW and when she would apply the brakes, I would hear a hissing sound, only when brakes applied. I thought nothing of it because we are holding air perfectly and she stops like she should. However, I was working on another coach (same chassis and drive train set-up) and his did not make any noises when brakes applied.

The noise seems to be coming from the exhaust area, this is what has me scratching my head...

Now, if I get in it after it has been sitting, lets say over night, and all the air is "dumped" from the system. I can fire her up, press on the brake and no noises at all... but, when it reaches 90-125 PSI area, if I press on the brake the sound i get is what is in the video.

She only makes a sound if the engine is on, no matter if parking brake is applied or not.

**** I have a video that will not load ****

She is a 2002 Ultimate Advantage with Cummins ISC 350 on a Spartan chassis.

Any ideas?

-Lupe
 
You can investigate this with the coach parked. Chock the wheels firmly, engine running and tranny in neutral, and you can apply brakes and listen. Air leaks are not unusual and the air system is designed to be able t cope with major air loss and still stop the rig. The brakes work fine at 50-60 psi.

The compressor and air regulation (governor) system is in the rear, just forward of the engine.  When you press the brakes, air demand goes up and the regulator does its thing.  Has the air dryer been serviced in the last few years?  24-36 months is the recommended interval and a dirty air dryer (desiccant cartridge) can cause problems in air distribution as well as allowing moisture into the air system.
 
Thanks for the reply Gary,

I purchased the coach last year, and I personally have not serviced the dryer yet. The transmission had NEVER been serviced, so I will assume that the dryer is in the same boat.

I just find it odd that i hear it through the exhaust pipe.. nothing correlates the two (brake pedal and engine)

-Lupe
 
Not sure what "I hear it through the exhaust pipe" really means.  And this with engine on or off? I wouldn't hear anything but exhaust noise with the diesel running! If the engine is off, that big pipe makes a dandy megaphone for any nearby sound.
 
Won?t leak with engine off? That eliminates quick release valve and brake diaphragm. I know nothing about exhaust brakes. All my experience is with compression and flywheel brakes, so I?m curious. Do they ever tie the exhaust brake activation to the brake pedal? ( via a switch of course)
 
Gary,

When the brake pedal is press (engine running) there is a noticeable tone change that sounds like hissing coming from exhaust area. If you have means of receiving a video, I can send. I?ve tried to scale it down for the forum, but it?s too large.
-Lupe
 
jubileee said:
Won?t leak with engine off? That eliminates quick release valve and brake diaphragm. I know nothing about exhaust brakes. All my experience is with compression and flywheel brakes, so I?m curious. Do they ever tie the exhaust brake activation to the brake pedal? ( via a switch of course)
Click to expand...

The Exhaust brake is activated by a switch, yes, not by the "service" brake pedal. Trust me, I am learning more about air brakes then I wanted to in the beginning!!
 
The exhaust brake has nothing to with the service brakes as far as braking mechanics.  It's part of the engine exhaust system and does not use the air system.  Typically, though, the exhaust brake dashboard switch is an On/Off that enables or disables it's use, but the activation of it for braking assist is via another switch tied to the brake pedal & accelerator peddle. There are a couple different methods of control so I'm not sure what you have.  Some systems are programmed to come on whenever the accelerator peddle goes to zero input while others require that plus a touch of the brake peddle as well.
 
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