I've searched high and low with no luck about anyone running an auxiliary finned cooler on an r53. I have an old ford truck that has a power steering cooler in front of the radiator along with a transmission cooler. I was thinking about taking the hose from the reservoir out to the radiator and installing a small finned cooler just like my truck and running it back to the pump. But I also have the thought that since no one has done it, there has to be a reason. Any insight?

 

Why are you wanting to run an additional cooler? What problem are you trying to solve?

 

Well since the aux fan goes bad keeping the pump cool, maybe cooling the actual steering fluid would help the pump last longer

 

The fan shouldn't go bad more than once during your ownership. Clean it up every time you're underneath the car, listen for noises as you spin the blade with your finger, and inspect for leaky hoses/reservoir. If the fan is clean and quiet, and there aren't any leaks introducing potential air bubbles, then it should be okay.

It would be so much harder to service the power steering system if you ran long lines to the front of the car. Not to mention the additional power steering fluid you'd need to include in the system to make up for the additional volume.

 

The pump fails not from heat, but because it isn't a brushless DC motor and simply wears out. You could think of it as a cost cutting move by BMW.

https://www.northamericanmotoring.co...ml#post1586866

 

FYI for the fan when it does fail:
https://www.northamericanmotoring.co...ml#post4266995