Has anyone ever blown a brake line on a downhill?

No, that hasn't happened to me thank God.

 

Do you have pics? Both lines broken? From your description it sounds like you hit some road debris.

 

I experienced an emergency braking situation this past Saturday on US-60 near Apache Falls between Globe, AZ and Show Low, AZ. I didn't lose an air line or experience a sudden loss of air pressure from the system like you but what occurred was one of the S-Cams on the left rear of my trailer got stuck from a piece of wood that I picked up somewhere along the way. The piece of wood was jammed against the S-Cam and the front brake shoe and it was making just enough contact to create excessive heat and so every time I pressed the brake it didn't take much for the shoe to make contact with the drum and it caused it to overheat. As long as I have pulled this trailer through the mountains I have never had an overheating issue on the truck or trailer brakes.

I saw a little bit of smoke on a 6% downhill and thought it was a glare or reflection in the mirror but when I had a dark colored vehicle behind me I saw the smoke and I thought "well great, here comes the fire extinguisher."

I was about a mile away from the end of the downhill and a place I could pull over. At the time I didn't know what was causing the single brake assembly to overheat so I used the yellow park brake valve to apply the truck brakes only at the same time while downshifting and using the Jake Brake as usual. I pushed the yellow valve in long enough to wind it up and drop two gears and then pushed the valve back in to release the truck brakes. I ended up utilizing the yellow tractor valve 3 times to get the truck down to 4th gear and then just let the Jake slow me down and pull in to the pull-off. I pulled up close to the mountainside off my right and turned the wheels into the dirt to keep the truck from rolling because I didn't want to set the brakes. I hopped out, tossed down a wheel chock and grabbed the fire extinguisher. Luckily I didn't have a fire but boy howdy was it hot.

I sat in the pull-off for two hours allowing the brakes to cool down, removed the piece of wood from the brakes and continued on down the road. I feel like if I hadn't ever experienced using the yellow tractor valve to apply the brakes while loaded and rolling I probably would have had a fire. My Dad taught me to use the park brake valve so I could learn how the truck would react in a situation like this and I thanked my Dad again Saturday night for teaching me that when I was a kid. At 82,000lbs. an issue with the brakes is never good, especially on a downhill run.

I agree with you as well that teaching new CDL holders about how to use the park brake valve is a good idea. It can save your life and somebody else's life too.

Thanks for posting your story.

 

Yeah man. I've never had to use that part of the training from my Dad when I was a 16yr old kid but I'm sure glad I knew how to utilize it to get the truck stopped.

I learned to use it in my Dad's 1986 Kenworth K100 cabover glider with a 3408 CAT and a 13 speed. Good times riding in that truck with Dad pulling a flatbed making money on the way to a family vacation with me and my sister in the sleeper or sitting on the doghouse and my Mom navigating from the passenger seat. Haha

 

No, not at all. I have pulled the yellow valve at 45,000lbs and 60,000lbs and it still has not locked up the brakes causing the tires to slide.

Now, this does not apply to every truck and trailer setup. There are several factors that come in to play when doing this. Cold brakes vs. hot brakes. Proper adjustment, wet vs. dry, road surface texture etc.

If you are going to test your setup and experiment with this style of emergency braking technique please do it at your own will and be smart about what you are doing. Having a controlled environment is best and without other cars around.