On December 3, 1999, at 1715 hours Pacific standard time, an Oehling Questair Venture, N3QV, veered off runway 25 and nosed over after encountering soft soil during landing rollout at the Auburn, California, airport. The airplane, constructed, owned, and operated by the pilot under 14 CFR Part 91, sustained substantial damage. The private pilot, the sole occupant, sustained serious injuries. The personal flight originated at the McMinnville, Oregon, airport at 1630, and an instrument flight rules (IFR) flight plan was filed. Prior to reaching the Auburn airport, the pilot cancelled the IFR flight plan due to prevailing visual meteorological conditions. Reported winds from the closest weather observation facility located approximately 60 nmi from the accident site were from 340 degrees at 14 knots, gusting to 18 knots. The pilot reported that there were no discrepancies noted with the approach or initial touchdown. He utilized his rudder and ailerons for directional control until midfield, when the airplane was slow enough to engage the brakes. He stated that there was very little response from the right brake and as the airplane was exiting to the left of the runway, he "pumped vigorously" on the right brake. After the airplane exited the dry runway, it went into a muddy field. The nose wheel dug into the mud and the airplane nosed over. The pilot stated that 1 month prior to the accident he had noted a leak in the right brake line. He had the brake line taken apart and found a small hole in the line. The line was replaced and then tested on three occasions, 1/2 hour at a time. The testing included fast taxis and takeoffs and landings. There were no discrepancies noted. A witness to the accident stated that the airplane landed approximately halfway down the runway; as the airplane continued the landing rollout, he lost sight of it because it went behind a row of hangars. He reported hearing the sound of metal on the runway, and then a pilot in the pattern reported that there was an accident at the departure end of runway 25. The ground witness reported that the winds were only 4 to 5 knots; however, he spoke to the pilot who reported the accident and he stated that he had to "crab into the wind quite a bit" for landing, but when he reached the threshold the winds died down significantly.