As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NO BRAKE PRESSURE ON PILOT'S PEDALS. TROUBLESHOT TO A LOOSE STOP SCREW ON RIGHT POWER BRAKE VALVE. THE SCREW HAD BACKED OUT ONE AND ONE-HALF TURNS WHICH CAUSED BRAKE PRESSURE FLUID BYPASS. ADJUSTED STOP SCREW AND RETORQUED NUT. SUBMITTER RECOMMENDS A MEANS TO SAFETY WIRE THE STOP SCREW AND JAM NUT.