Hi I'm having problems changing the serpentine belt on my 2003 R53 using my tool out that I made years ago based on the plans in the Haynes manual and the same piece of rod that I used previously as "the pin.". When I compress the tensioner, the rod goes in too easily, after I barely compress the tensioner at all and there's not enough tension taken off the belt in order to remove it. When I look at the the tensioner prior to my taking any tension off of it I see at least half of the second hole is already exposed, which doesn't seem right. I recall that the top of the hole was barely visible at all prior to compressing the tensioner when I did this previously. The belt had probably been on the car for close to a decade, probably 50,000 miles. I'm wondering if my belt is maybe slightly too tight. Although I don't understand how that could be since it's the same belt that I installed previously by myself. I would expect a belt to maybe stretch slightly after use, not shrink. I've tried wedging a large flat bladed screwdriver under the pin, but it still doesn't take off enough tension. I've thought about cutting the belt off after I get the pin in,

 

I cut the belt that was on the car and removed it. It was a Continental 6pk1374. Every auto parts store's website gave a different number Continental belt for my car, but most listed a length of 54.7" or so. Fcpeuro recommended a 6PK1388. Continental's website recommended a 4060547, which is a 6PK1390. I measured my old 6pk1374 at 54+3/16". It appears that 1374, 1388, 1390 are the length of the belt in mm. So my new belt is 16mm longer than my old one. The new belt is much easier to install. I have so idea how I got the old belt on my car, could it have shrunk?

 

Rock Auto would seem to concur with both the 6PK1388 as well as the 4060547.
https://www.rockauto.com/en/catalog/...rive,belt,8900
This also checks with RealOEM part number,11287520199 shown as item #2:
https://www.realoem.com/bmw/enUS/sho...diagId=11_3394