My car was off line for 3 weeks to replace the fuel injection pump and brake hydro boost.The day that I got it back, I took it around the building to test the brakes before leaving the property. After a 17 mile trip on the highway, I reached my exit. I let the slow to about 45 mph before reaching the off ramp. At the top of the ramp I stepped on the brake pedal and it went to the floor. I said, "Oh !" and pulled the parking brake knob(I had a Ford P1000 with the Lucas parking brake). The rear brakes locked up at 40 mph and I left about 75 feet of skid marks before it stopped. I was lucky that the traffic light at the bottom of the ramp had just turned green. The usual line of cars was gone. I was aiming at that light in case the truck wouldn't stop because there were 4 lanes of traffic that I would have to cross. They brought me out a spare and the day mechanic discovered the problem. A cotter pin that holds the brake linkage together was installed from the bottom instead of the top and the ends were not bent over. While on the highway it fell out and the linkage vibrated apart. Thankfully I didn't have a regular hand brake because I would still be going.