What was found
AFTER ENG START, DUCT PRESSURE #2 DUCT INDICATED NORMAL POST. ENG START PRESSURE DURING CLIMB AFTER T/O, DUCT PRESSURE #2 INDICATED 5-10 PSI. (#1 WAS APPROX 40 PSI) A/C WAS PRESSURIZING NORMALLY. CLIMBING THROUGH 10,000 OR SO DUCT PRESSURE #2 POPPED UP TO APPROX. 40 PSI AND REMAINED AT NORMAL PRESSURE FOR REMAINDER OF FLIGHT. GROUNDED - YES. PERFORMED B737-800 AMM TASK 36-11-00-700-802 ENG BLEED AIR SYS LEAK CK WITH APU, FOUND PRSOV MANUAL OVERRIDE NUT WITH SOME PLAY AND HAS TOO MUCH LEAKAGE, REQUIRES R/R OF PRSOV. P DIAZ 77613. REMOVED & REPLACED #2 ENG PRSOV, REF MM 36-11-04-000-801 & MM 36-11-04-400-801. OPS CK GOOD. NO LEAKS NOTED.