FYI, I noticed this little aberration a few years ago: a standard box end wrench was just'a little bit too thick to get in between the pulley on the tensioner and the bolt.

Solution: just grind (I used a Dremmel) a shallow recess on the interior side (typically the side angled "in" vs. the side angled "out") that allows you to slip the box head between the two.

I found I had to use a hammer to initially break the tensioner bolt free (I think the OFFICIAL MB-Approved tool has about a 4 foot handle and the "boys" crank on that baby like it was a RR track switch!!)...

"Tap, tap, tap, (Curse!) tap..... Ah!

There is also a "flat" on the tensioner arm where you can put an adjustable wrench (if it is skinny enough) or an open-end wrench to put some tention on the belt by lifting up. There is room (at least there is on a 420SEL) for both your hands and the two wrenches.

I have one of these at both houses because you just don't know where a belt will break. You can drive a bit without a/c, air pump or even the alternator belt, but not far without the water pump and p/s belts.

Cheers!

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'91 420 SEL @ 199K, '92 SVX @ 181K, '93 SC400 @ 86K, '93 Kaw ZX-11 @ 30K, '87 F250 @ 181K , 2001 Valkyrie Interstate @ 6K, Y2K Honda NightHawk 250 with 1.5K, '88 420SEL I.@ 179K & the 2nd latest, an '88 420SEL II.@ 210K runnin' parts car, '85 F150 300/NP435