CUSTOMER CONCERN Engine runs rough for several seconds on the first cold start, coolant level drops over time, and the PCM stores DTCs P0302 and P0316. CAUSE Confirmed failed cylinder head gasket allowing coolant intrusion into a cylinder during cool-down. CORRECTION Remove the cylinder head, replace the failed head gasket, refill and bleed the cooling system, clear DTCs P0302 and P0316, and verify cold-start operation.

CUSTOMER CONCERN Customer states the engine overheats while driving and the heater blows cold. Coolant temperature reaches approximately 230°F with the cooling fans operating. CAUSE Cooling-system bleeding and flow checks confirmed combustion leakage from a failed cylinder-head gasket. CORRECTION Remove and replace failed cylinder-head gasket. Refill and bleed engine cooling system and verify normal operating temperature.