What was found
THE THERMOSTATIC OIL COOLER BYPASS VALVE WAS REPLACED AT OVERHAUL OF THE ENGINE BY CLYDESDALE AIRCRAFT. THE ENGINE WAS INSTALLED IN A CESSNA 172 SKYHAWK. A TEST FLIGHT SHOWED VERY HIGH OIL TEMP. THE OIL COOLER WAS COLD TO THE TOUCH. THE OIL BYPASS VALVE DID NOT OPEN. A NEW VALVE WAS INSTALLED, OIL TEMP WAS SATISFACTORY. THE DEFECTIVE VALVE WAS INK-STAMPED, A1Q95. THE DEFECTIVE PART WAS RETURNED TO CLYDESDALE AIRCRAFT FOR WARRANTY. THIS VALVE IS USED ON OTHER LYC ENGINES.