I have a Snap-on 10mm box end wrench that fits perfectly with no mods on the fan bolts. Sounds like you found one that will work just as well. Make sure the fan bolts are on snugly. Don't over tighten them, though. It's one of those do it by feel things but if you tighten them to the point where the wrench wants to slip off, that is probably more than needed.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Never say never. I've never had to either, until this baby. PBd the you know what out of it, trief everything and that pump won't budge. The housing bolts didn't give me any problems (actually came out very easily).

Not MB but, 6.2 GM diesels the water pump is bolted not to a housing, but a plate. I removed 'all' the pump bolts & thought man that pump is really glued on! Turns out the pump has bolts through the plate into the pump from the back side, and, yes, you can bend that plate with a pinch-bar. (its about 1/4" thick)

-c-

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I have the shop manual, but didnt bother looking, 'just remove the bolts, and wallah!'

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"I applaud your elaborate system of denial"