2006 MCS convertible. I changed my original belt a few years ago for a Dayco 5060548 (54.75 inches). I am second guessing my choice because I don't see any holes on the tensioner (remember reading here somewhere that you should at least see 1 hole if the belt is still good). Now I know it couldn't have stretched that much since it probably has 5k miles max on it (summer driven weekend car). Browsing on rockauto, I noticed belt lengths ranging from 44 inches to 55.25 inches. Does anyone know what the official length should be for a stock MCS (no supercharger pulley upgrade)?

 

 

 

I guess the belt I had installed was good then. Maybe there is something wrong with the tensioner. Any way I can test it.

 

Unless the tensioner is moving about or vibrating badly, and belt flapping around loosely, there's nothing wrong with it. As to how many holes ~should~ show on the protruding tang, I haven't read anything on that. The holes are there to de-tension the spring whilst changing the belt; not to gauge overall health of the belt.

I changed my belt and tensioner two-years ago, and took a pic of my tensioner just now.
Guess what? No holes showing, and I'm not worried...

Motor on!