2004 BMW 745Li Engine Oil Cooler Replacement Cost

An engine oil cooler is a small device that looks much like a radiator, works much like a radiator, and is mounted near the radiator. Air passing over the oil cooler will lower the temperature of the engine oil, and allow the engine oil to remain much more effective. This will prevent the engine oil from becoming too thin for normal operation.

This component is part of an extension of the engine oil system, where an oil feed line will constantly fill the oil cooler, and an oil return line will constantly drain that oil back into the radiator. While the oil is being passed through the oil cooler, it is being cooled because of tiny metal fins that are attached to the oil cooler core are in constant contact with flowing air, and since they are so thin they cool very quickly. This is a highly reliable and effective means of cooling engine oil which is hot from the process of combustion inside the engine. Especially during extreme operating conditions or with forced induction engines, the oil cooler helps maintain the viscosity of the oil, preventing oil breakdown and sludge buildup, and allows the engine to remain protected in the harshest of conditions.

Oil coolers seldom fail except for two main reasons. Leaks are the leading cause since the oil cooler is always under pressure and hot. The oil lines, seals, and oil cooler core will eventually wear out, and small perforations or seal degradation will take hold causing the oil cooler to need replacement or resealing of the oil lines. This will be obvious as an oil leak will be coming from somewhere other than the engine, most likely somewhere around the front bumper cover. Also, if the oil cooler cannot pass oil through the cooler core, the cooler will block oil from returning to the oil pan, and the check engine light will likely illuminate due to the knock sensor detecting clattering from oil starvation. Finally, the check engine light or oil temperature warning light will likely come on if the oil cooler is blocked by debris from the front, or if the fins on the oil cooler have become bent over the course of time. This, however, does not often require replacement, as there are specialty combs made to straighten and clean the fins on the engine oil cooler to restore functionality. Also note, a severely leaking oil cooler will illuminate the oil pressure warning light, as will a clogged engine oil cooler or engine oil cooler line.