Complete brake failure while towing...

[cattlerepairman]

If a US air brake system loses system air pressure, the "spring pack" diaphragms will stop holding back the spring brakes, and the spring brakes will fully apply the brakes stopping the truck very rapidly. This spring brake doubles as a parking brake when the ICC valve is left in the open position. So, with a US air brake truck, the truck cannot move if there is insufficient air pressure in the braking system
-Chuck

Chuck, I think what he is saying is that in other jusrisdictions, even the air brakes are "multi-circuit". He describes the multl-circuit protection valve which basically isolates any air brake circuit that leaks.
That way, you likely have some service brakes left and do not immediately default to the spring brakes locking up on you.

If you look at the air brake technology used in other comparable countries, our North American standards do look a little antiquated.

 

[cranetruck]

There is an article in MVM by yours truly; "How to safely drive downhill" , Issue #108, April 2005. I experimented a little with engine braking at the time and ended up installing an exhaust brake on the deuce...

 

[clinto]

What's weird is that my electric trailer brakes didn't work either once all the fluid was drained.



The parking brake has ZERO affect on 23k lbs rolling at any speed.

1. I wonder if the issue here is that since the system was no longer applying pressure, it didn't trigger the brake controller-brake controllers have to be wired into the brakelight circuit so that they know only to work when the brakes are applied. Since you had no fluid, I can see the system being unable to actuate the brake light switch. I would definitely say this is the case if your truck has the old school brake light switch in the break fluid pressure port, not sure how it would work if you have the new style air pressure switch.

2. I am going to refer to your quote every time I hear someone try to justify deferred maintenance on their truck by saying they will just pull up the parking brake.