A technician will look for signs of a leaking engine oil cooler hose. Often, this involves raising the vehicle, removing underbody shields to access the lines, and looking for the leak. Sometimes the leak is harder to see. A technician can follow a procedure where dye is added to the oil and a black light is used to highlight the leak. But most engine oil coolers and lines are easier to see and do not require this procedure.

To replace a bad engine oil cooler line, a technician will disconnect the line at each end and trap any oil that leaks out in a drain pan beneath the vehicle. Sometimes it is necessary to drain the oil completely before removing the cooler lines. The lines may be screwed in at each end, or they may have special connectors. If the oil cooler is embedded in the radiator, the lines can be difficult to reach. It may be necessary for a technician to remove a significant amount of adjacent components, including coolant hoses, for access. With the old line removed, a new line is installed and the oil is topped off. If engine coolant is lost in the process (on some vehicles), the fluid is also topped off and a procedure is used to make sure that the cooling system is purged of any trapped air.

To avoid premature failure of the oil cooler and its components, regular vehicle maintenance should include oil and filter changes at the manufacturer's recommended intervals. Old, dirty oil and engine sludge can clog the engine oil cooler.

The oil cooler lines can retain oil pressure even when the engine is turned off. Caution should be exercised when disconnecting the lines.

Access to the connections of an engine oil cooler line is usually limited, and surrounding shields and mechanical components frequently need to be removed to perform this repair. The front bumper may even need to be removed. The vehicle may need to be lifted and supported off the ground to accomplish this. The connections for a cooler line often become corroded and they can be very difficult to remove, especially without the proper tools. Only someone with intermediate to advanced DIY experience should attempt to replace the engine oil cooler lines.