What was found
DURING CLIMB DUCT PRESS L DUCT PRESS 18 PSI RIGHT DUCT 40 PSI. WHEN LEVELED AT FL 370 R DUCT 40 PSI & LEFT 28 PSI. GROUNDED - YES. INSPECTED #1 ENGINE PNEUMATIC SYSTEM AND FOUND SENSE LINE BETWEEN BLEED AIR REGULATOR AND PRE-COOLER CONTROL VALVE TO BE CRACKED AT THE T-UNION. REMOVED & REPLACED SENSE LINE REF B737-900 AMM 36-11-03. COMPLETED ENGINE BLEED AIR SYSTEM CROSSOVER OPS TEST REF 36-11-00-710-801. OPS TEST GOOD. ALL ENGINE PNEUMATIC INDICATIONS NORMAL. NO BLEED TRIP LIGHT ILLUMINATED AT THIS TIME.