What was found
(CAN) AFTER TAKEOFF IN MINUS 42 DEGREES CENTIGRADE AND BLOWING SNOW, THE LANDING GEAR TOOK 3 CYCLE ATTEMPTS TO RETRACT. SUBSEQUENT RETRACTIONS WERE NORMAL AS THE AIRCRAFT APPROACHED WARMER CLIMATES. BEFORE LANDING AT HOME BASE, AND GEAR EXTENSION, A NOISE SIMILAR TO AN AIR LEAK WAS HEARD. IT WAS DETERMINED THE THERMAL HYDRAULIC RELIEF VALVE WAS OPERATING AT A LOW PRESSURE. VALVE WAS REPLACED.