Engine oil cooler does the function of removing excess heat from the engine. The oil flows through the tubes while the coolant flows around these tubes. When this engine oil cooler (or simply coolant) goes bad, it damages the engine. Other damages and signs of the engine oil cooler gone bad are:

• Oil leak
• Coolant leak
• Coolant and oil mixing
• Leakage of oil in the cooling system

There is no fixed time of changing or refilling the engine oil cooler. The only way to prevent it from going bad is to check it regularly.