What was found
AT 33000, NOTICED DUCT PRESSURE SPLIT RIGHT SIDE AT 45 PSI AND LEFT SIDE AT 7 PSI. CABIN ALTITUDE WAS CLIMBING. DESCENDED TO 25,000. CABIN PRESSURE OK N1'S 82.0, N2 91.0. OAT 29 DEG CELSIUS GROUNDED ACFT. NR 1 ENG PERFORMED FIM TASK REF FIM-36-10-00-810-804. PRECOOLER VALVE PRSOV BLEEDAIR REG ALL CHECK GOOD. FOUND MASSIVE LEAK IN CONTROL FLEXIBLE SENSE LINE FOR PRSOV. REPLACED LINE REF FIM PG 11 STEP 2. 36-10-00-810. LEAK CHECK GOOD. ACCOMPLISHED REPAIR CONFIRMATION REF FIM-36-10-00-810-804 ITEM G. PARTIAL WORK ACCOMPLISHED. PRIOR TO LEAK CHECK AND REPAIR CONFIRMATION.