[Brzic]

I decided to change the serpentine and power steering belt on my E91 from 2007. (the engine is M47S) by myself. But before I begin I have 2 questions.

1. I know that the serpentine belt is tensioned by a belt tensioner (spring loaded) and I need to release the tension with a wrench in order to replace the serpentine belt, but how's power steering belt tension accomplished? And how do I release the tension from the power steering belt in order to put a new belt on?

2. Belt lengths. I know that the OEM number for the serpentine belt is 11288477780 and for the power steering 11287791786, but I was unable to find the exact lengths of those belts, for example, I found a serpentine belt with OEM number and it's length is 1830 and from different manufacture (with the same OEM number) the length is 1836. The same goes for the power steering belt, is the length 810 or 830?

[nomiS330d]

Mines got electric steering so only has one belt but I guess the tensioners are the same. Both belts will have a spring loaded tensioner which you use a large torx bit to release the tension to get the belt on and off. If you feel directly below the bolt that’s in the centre of the pulley you should feel it. You will need to remove the cooling fan for better access.

[nomiS330d]

Just had a look on google and it seems your tensioner is different to mine but the way of releasing the tension is the same. What you are looking for is this-
https://i.postimg.cc/Qd9mJqWX/72-C51...-A5-B1-CD3.jpg