I've looked at some threads....and have a laptop STAR w/WIS, which wasn't much help for this job.

My beloved 2011 E550 had the notorious noisy idler pulley at 84K miles. I planned on swapping the belt and tensioner at the same time. Jacked up the front, pulled the bottom plastic cover, and used a breaker bar to loosen tension/move the belt enough to replace the idler. I gave up on inserting a pin in the tensioner b/c there's barely enough room for the breaker bar. I work cautiously, so this alone took 90 minutes, and have nice cuts from the fan shroud edges. Glad I had the idler on hand, it went from slight squeal to damn near seized overnight. The tensioner is quiet, and the belt looks great, so I'll fight that battle another day.

Those of you who have done the tensioner and belt, did you do it from the top or bottom (while on your back)? Did you bother removing the fan shroud, or just fight the cuts and fiddly nature?

Thanks everyone!

Surprised this never got a reply.
Going to do it in the next few months and not looking forward to it
I attempted a leakdown test which requires turning the crank bolt and same, fan shroud cut my arms up like crazy