BMW 740i xDrive Trans Oil Cooler Line Replacement Cost

The transmission cooler lines carry transmission fluid back and forth between the transmission, and an external or radiator integrated cooler. They are often part or wholly metal, and screw in the transmission and transmission cooler at either end. The transmission fluid starts in the transmission, where work performed generates heat. It is then pumped to the transmission cooler where it sheds excess heat, and then returns back to the transmission. Heavy duty applications such as high performance vehicles, off-roaders, and tow-vehicles often utilize this system.

Finding drops of oil under a vehicle can be unpleasant, mostly because identification of the leak can be a daunting task. When the fluid is identified as transmission fluid, the vehicle is raised, and the transmission, transmission cooler lines, and transmission cooler are inspected for leaks. If the transmission cooler lines are leaking, the leak will originate at the cooler, a connector, or a soft line. This will be very noticeable, especially if the transmission, transmission fluid lines, and transmission cooler are cleaned prior to inspection.

Driving with a leaking or broken oil cooler line is not recommended as the amount of transmission fluid that is lost cannot be calculated while driving, and the cooler, and cooler lines for the transmission are able to leak a great amount of transmission fluid very quickly. Besides pouring transmission fluid onto the ground, the vehicle may suffer transmission failure from lack of lubrication. Get this fixed by a RepairPal Certified Shop

There is no specified replacement interval for transmission cooler replacement lines. However, high mileage vehicles may experience failure of these lines as their rubber parts will degrade over time due to age and heat from driving. More likely, the transmission cooler itself may fail, and the lines will be recommended as part of the repair. Transmission coolers can fail due to heat (in regards to radiator integrated ones) or due to collision.

When any transmission symptoms are present, the technician will first conduct a visual inspection of the vehicle, and note any observed issues. If the transmission issue is related to a leak on the transmission cooler or transmission cooler lines, those components will be inspected, and either resealed, or replaced. n the transmission. Once the suspected component(s) have been tested, any failed component must be replaced, and the transmission will be tested once again. Failed transmission cooler components are typically very easy to notice for the experienced technician.

Leaking transmission cooler line replacement is normally done without draining the transmission fluid, but the transmission oil cooler must be drained once the first line is disconnected from the transmission. After the transmission cooler stops pouring fluid from the lines, the remaining connections can be disconnected, and the new lines placed into existing retaining hardware. Once the transmission fluid cooler lines are reconnected, the servicing technician will refill the transmission with new fluid prior to reconfirming the repair.

We recommend comparing the factory part to an aftermarket part, and ensure the bends in the line are all correct. Many lines will not be correct when they are ordered, and must be bent into shape using specialty tools. This should be considered if planning on taking this project on as a DIY.

There are many types of transmission fluids, and they are not typically interchangeable. Consulting the owner's manual for your vehicle is the best way to ensure you have the correct fluid for your transmission. If improper transmission fluid is added, the resulting damage could be severe.

Most experienced DIYers can replace the transmission lines for the transmission fluid cooler. The experience is needed to ensure the fasteners are tightened properly to prevent leaks, but not so tight they cause them. If the manufacturer specification for those fasteners are followed, the task should not be a problem.