Fixing a brake line at Minus thirty

Field training for Alaska army units is conducted almost exclusively in the winter. Anyone can fight when it is warm but surviving and operating in sub-zero weather takes training, endurance and a lot of preparation. It was not unusual for us to be out in the field for over a week and never see a high temperature above negative 10 Fahrenheit (-10F). As a wheeled vehicle mechanic, my mission was to make sure that the vehicles were prepared for the weather and to also fix them when there were breakdowns in the field.

There were always the normal items you would run across in the winter. Dead batteries were by far the most common issue since batteries have no love of the cold. There was also the heater will not work or other mundane things like changing a flat in a foot of snow. One of the more challenging fixes I had the pleasure of doing involved a busted brake line on a M35A2 two-and-a-half-ton truck when were ready to return to the base at the end of our latest exercise.

M35s used a hydraulic brake system with an air assist. (Not my design) This brake system was touchy at best and required you to treat it with the utmost respect (Draining the air tanks every night after you were finished for the day, etc.) In this case, the timing was lousy. We’d already packed up and were ready to move out when the driver noted the brake pedal going to the floor. As this was an indication of a fluid leak, we troubleshot the hydraulic portion of the brakes and not the air assist. We quickly identified the point of failure as a broken flex line from the chassis to the center axle on the driver’s side.

As luck would have it, we didn’t have the line in spare parts, so we had to improvise. We figured out that we could disconnect the flex line at the junction box and all we had to do was come up with some way of blocking off that connection. Once blocked, we could refill the brake fluid and bleed the air from the hydraulic lines, and use the brakes on the five remaining wheels to get the truck back to base.

The truck is sitting in a couple feet of snow. This would normally have been a handicap, but in this case, it gave us a place to lay where we had easy access to the junction block. It was getting to be late afternoon and the biggest challenge was the falling temperatures. Staying warm was getting harder and we were trying hard not to have to spend another night in the field.

As it is always said, necessity is the mother of invention. After we’d exhausted all possible spare parts scavenging among other local units, we looked hard at what we had available and the solution was to use part of the failed hose assembly. Hydraulic flex lines have a metal fitting and line on each end and it was the braided rubber hose in the center that had failed. We cut the metal line as close as we could to the hose and made a plug out of it. Using a vice mounted on our wreaker, we crimped, then folded and then crimped the cut end of the metal line, closing the end of the line. Then we placed the line upon end up in the vice and heated the line with a torch and filled it with solder to seal the crimped end for high pressure.

Once it cooled with a quick dowsing in the snow, we had a pressure solid seal for the missing line at the junction. We quickly blead the air out of the lines and we were rolling in about 30 minutes. This allowed us to return to base just before dark and sleep in a warm bed for the first time in over a week. Field expedient repairs for the win again!