Could be either. BMW PS pumps are known to leak. Check the fluid level. If you haven't done it before, also replace the fluid. You could get under it and drain by disconnecting the hose but you don't necessarily have to. I used a turkey baster to extract the fluid from the reservoir then just added fresh fluid in. I added the Texaco 7045E ATF as I had some on hand from a previous transmission job. The PS units call for ATF. It should say it on the cap of the PS reservoir.