What was found
TAKE OFF POWER APPLIED SUDDEN AIR SURGE FROM ACFT, DURATION 5 SEC, AT ALTITUDE SAME THING, DURATION CONTINUOUS. DUCT PSI: CLIMBOUT L35, R20. LEVEL FLIGHT 30, 28 AFTER THAT 38, 42. ACFT GROUNDED. PERFORMED FIM TASK 36-10, TASK 804 ON NR 1 ENGINE STEPS E. (16)(A) & (B) & PRECOOLER HEALTH CHECK IAW 36-12-00 & ENGINE BLEED SYS HEALTH CHECK IAW 36-11-00. NO FAULTS FOUND, REPLACED PRE-COOLER CONTROL VALVE SENSOR 390 & 450 THERMOSTAT IAW AMM 36-12-93 & AMM 36-11-05. PERFORMED FIM TASK 36-10, TASK 804 ON NR 2 ENGINE STEPS E. (16)A & B & PRECOOLER HEALTH CHECK IAW 36-12-00 & ENGINE BLEED SYS HEALTH CHECK IAW 36-11-00. FOUND NR 2 PRECOOLER CONTROL VALVE. OP LK NORMAL. REF MM 36-12-02. BOTH ENGINES DUCT PRESSURE NORMAL DURING REPAIR CONFIRMATION, REF FIM 36-10, TASK 804.