The common oil cooler failure symptoms usually relate to leaking liquids. If the oil cooler adapter fails as mentioned above, engine oil may be forced out of the engine. If it is only a small oil cooler leak, it might be a puddle of engine oil on the ground underneath your vehicle or if it is larger it could quite possibly be a stream of oil on the ground behind your vehicle. If either of these is the case, you should get it checked out at a garage as soon as possible. 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.
Another liquid that the cooling system can lose is engine coolant. Similar to a loss of oil, engine coolant can leak out of an oil cooler if the body of the cooler is compromised. Whether the coolant leak is large or small, the engine is going to overheat after a while 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 bonnet of your vehicle. If enough coolant leaks from the radiator or oil cooler, it can result in engine overheating problems and mechanical component failure, so get it checked out as soon as possible!
Mixing liquids can also be a sign of a problem with the oil cooler. If the oil cooler adapter fails internally (rather than externally, as mentioned above) 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. This can also happen in reverse and coolant can get into your oil supply. For both of these, the cooling system and the engine both need to have all the liquids flushed out. If your oil cooler adapter has failed, this will need to be replaced. The oil cooler itself will of course need to be replaced if there is a leak.
If you have to repair your oil cooler or aren't happy with how it is performing, you could think about an oil cooler upgrade. There are a variety of aftermarket kits available.
