Symptoms of a Bad or Failing Oil Cooler

oil cooler

The oil cooler on any production vehicle is an essential engine component designed to keep modern cars, trucks, and SUVs running smoothly on the roads they travel daily. Whether you have a 2016 BMW or an older, yet reliable 1996 Nissan Sentra, the fact remains that the cooling system on any vehicle must be in working order during all types of weather and driving conditions. Although most drivers never have interaction with their oil coolers, keeping them in working order will extend their lifespan. However, like any other mechanical component, they can and often will wear out.

The purpose of the engine oil cooler is to allow the engine’s cooling system to remove excess heat from the oil. These types of coolers are usually of the water-to-oil type of heat exchanger. In most vehicles on the road, engine oil is fed to the oil coolers from an adapter that is located between the engine block and the engine oil filter. The oil then flows through the tubes of the cooler while the engine coolant flows around the tubes. The heat from the oil is transferred through the walls of the tubes to the surrounding coolant similar in many ways to the operation of an indoor air conditioning for residential homes. The heat absorbed by the engine’s cooling system is then transferred to the air as it passes through the vehicle’s radiator, which is located in front of the engine behind the grille of the vehicle.

If the vehicle is serviced as required, including routine oil and filter changes, the oil cooler should last as long as the vehicle's engine or other major mechanical components. However, there are some occasions where staying on top of maintenance will not prevent all damage potential for an oil cooler. When this component begins to wear out or has broken, it will display a few warning signs. Noted below are a few of these symptoms that can alert a driver that their oil cooler may need to be replaced.

1. Oil leaking from oil cooler

One of the components that are part of the oil cooling system is the oil cooler adapter. The adapter connects oil lines to the cooler itself and another adapter sends "cooled" oil back into the oil pan. Within the adapter is a gasket or rubber o-ring. If the oil cooler adapter fails externally, engine oil may be forced out of the engine. If the leak is small, you may notice a puddle of engine oil on the ground underneath your vehicle or quite possibly a stream of oil on the ground behind your vehicle.

If you notice any oil leaking under your engine, it's always recommended to contact a professional mechanic so they can determine where the leak is coming from and repair it quickly. As oil leaks, the engine loses ability to lubricate itself. This could result in increased engine temperature and premature parts wear due to increased friction from the lack of proper lubrication.

2. Engine coolant leaking from oil cooler

Similar to a loss of oil, an external oil cooler failure may force all of the engine coolant out of the engine. Whether the coolant leak is large or small, you will eventually overheat the engine if it isn’t repaired quickly. If the leak is small, you may notice coolant puddling on the ground underneath your vehicle. If the leak is a large one, you will probably notice steam pouring out from under the hood of your vehicle. As with the above symptom, it's important to contact a professional mechanic as soon as you notice a coolant leak. If enough coolant leaks from the radiator or oil cooler, it can result in engine overheating problems and mechanical component failure.

3. Oil in the cooling system

If the oil cooler adapter fails internally, you may notice engine oil in your cooling system. This happens because when the engine is running, oil pressure is greater than cooling system pressure. Oil is forced into the cooling system. This will eventually cause a lack of lubrication and can severely damage your engine.

4. Coolant in the oil

When the engine is not running and the cooling system is pressurized, coolant can be forced from the cooling system into the oil pan. High oil pan levels can damage the engine by the crankshaft slapping the oil as it rotates.

Any of these symptoms will require flushes of both the cooling system and the engine to remove all of the contaminated liquids. The oil cooler adapter, if it is the failed component, will require replacement. The oil cooler will also need to be flushed or replaced.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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