Brake pressure drop while backing

[Hemiterry]

I drive an 06 International 5600i tandem dump truck with an ISX15 and Allison RDS transmission. When loaded and backing downhill my brakes sound horrible and my air pressure drops to warning level very quickly. I have no braking or air issues any other time but backing downhill loaded. Does anyone else have this problem or know why it’s doing this ?

[tree98]

Try driving down the same hill loaded going forward instead of backward. It could be that the direction of travel has nothing to do with it. Could be that the hill your backing down is steeper than most your driving forward down and your on the brakes a lot harder than just normal driving????

Sounds like a bad air leak somewhere to me, maybe a brake chamber, valve, etc. Chock your wheels, turn the key on(engine not running)release the parking brake and push the brake pedal down. A leak as severe as your describing won't be hard to hear.

If you still believe it's only while in reverse, put it in reverse and see if you hear anything.

[Rawze]

Check there are no air leaks while the brake pedal is held down firm to the floor. Fix any leaks and replace any leaky chambers.

You need to also check that the air tanks are not filled with soot(carbon), water, or some other contaminant like oil etc. Maybe the volume of the air tanks has been compromised.

[hookliftpete]

Had a similar issue where one service chamber would leak while braking only, combined with being on the brakes while going backwards, the compresor could not keep up, as it was running at idle.

[Hemiterry]

Thanks guys, I’ll check everything out tomorrow and let you know what i find.

[Hemiterry]

Hey I just wanted to let y’all know that I found a leaking diaphragm on one of my rear brake canisters, hopefully that explains my air pressure dropping. I’m going to disassemble the front brakes next weekend to see if I can find anything causing the noises up front.
Thanks, Terry