Engine oil is used to lubricate the internal moving parts inside your engine. As the oil passes over and through these components, it also cools them down by absorbing heat. When the oil becomes too hot, it begins to break down, to degrade. At that point, it no longer protects your engine as it should.
To prevent excessive heat from building up in the engine oil, some vehicles come equipped with an oil cooler. The oil cooler is usually an aluminum box with small tubes or passageways inside of it. Some of these passageways carry oil. Others carry engine coolant. A thin layer of aluminum separates the two liquids.
When oil passes through the oil cooler, some of its absorbed heat is transferred to the engine coolant. And, just as is the case with the rest of the engine cooling system, the coolant flows to the radiator where the heat dissipates into the atmosphere.
Passing through the engine oil cooler are both oil and engine coolant, or “antifreeze”. Each liquid is present at a high temperature and under pressure. If the oil cooler develops a leak, a significant amount of fluid can be lost and lead to catastrophic engine failure. Additionally, if the partition that keeps the fluids separate deteriorates, oil and coolant can mix and cause problems.
Signs that your engine oil cooler is failing include: