What was found
(CAN) RECENT MAINTENANCE HISTORY SHOWED THE L1 DOOR SEAL WAS INTERMITTENTLY NOT INFLATING. THIS HAD CAUSED AN AIR TURNBACK AND THE SYSTEM TESTED SERVICEABLE FOLLOWING THE APPLICATION OF HEAT TO THE AIRCRAFT. THE SEAL FAILED TO INFLATE DURING SUBSEQUENT TROUBLESHOOTING AND THE DOOR SEAL PRESSURIZING VALVE WAS REPLACED AS WAS THE DOOR SEAL. THE L1 DOOR SEAL WAS ALSO FOUND TO HAVE A CUT AND SOME ENTRAPPED WATER. FOLLOWING THE REPLACEMENT OF THE PRESSURIZING VALVE AND SEAL THE SYSTEM WAS TESTED SERVICEABLE AND THE AIRCRAFT WAS RELEASED FOR SERVICE.