The only reason to ever own a 12 point wrench or socket:

Head bolts on a Jeep 4.0 (1/2" 12point)

Rear axle flange bolts on a Ford (12mm or 13mm 12pt)

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

...and also the 10mm 12point lower front shock mounting bolts.
W123 Front Shock Replacement DIY

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Famous last words right there.



All my wrenches are snap on. They're good, but the bolt is ultimately the final arbiter in deciding if he'll be giving you a bad day or not. Had that same bastard bolt on the fan clutch round that OP is talking about using the 12 point end of my wrenches. Ultimately used the open end and a small small hammer which shocked him loose.



Sorry to be the devil's or in this case, Murphy's advocate.



Your luck might be better than mine!

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-Typos courtesy of my mobile phone.

You got me there.
Thanks for the reminder about that piece of krap bolt. So far as I can tell, it is a rare example of bad design on my W123 M-B using a 12-point bolt in that spot. Why?
That location is prime territory for water and dirt. If there is anywhere on the vehicle where a 6-point bolt would be best, I consider that a good spot. As part of a front end rebuild a few years ago and after a highly unpleasant experience removing the old 12-point bolt, I replaced it. Good riddance.

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The fact is, a six-point wrench is superior to any other when used on a six-point hex head fastener. If you had used a six point wrench on your fan clutch bolt you would have had a significantly less likely chance of rounding the hex fastener than when using any other wrench design.

The only reason to use a twelve -point wrench is either on a twelve-point double hex fastener OR when the swing of the wrench is insufficient to allow the fastener to rotate at least the 60 degrees in order to reset the wrench for a subsequent pull/push.

Another common MB use of twelve-point fastener are the fly-wheel to crankshaft waisted - stretch to torque bolts used in manual transmission installations.

For people who anticipate working with their tools and their hands wrenching recognizing that preparation and proper tool use is the best way to avoid doing damage and subsequent repairs that require time and ultimately money is a sound way to remain profitable.

Another little trick I learned long ago, when setting up to remove a fastener apply pressure to tighten a fastener first. That way you risk buggering the fastener in that direction when breaking the initial bonds between the faster and what it secures. if you can get it to budge even a tiny bit you're likely home free when loosening it further.

Thanks for the lesson mate, but if you notice in post 10 I already mention I invested in a flare nut wrench set to avoid this nightmare in the future. OP is talking about his 12 point not fitting. We're beating around the bush at this point.

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-Typos courtesy of my mobile phone.

What advantage does a flair nut design wrench have over a six-point box design wrench when working on these fan bolts?

The benefit of being able to convince my wife why I need another set of wrenches, especially ones that do slightly more than just a closed 6 sided set.


It's the most important benefit of all.

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-Typos courtesy of my mobile phone.

I just went through the exercise of installing the plastic fan and fan shroud on my 85 300D, getting it ready for sale (putting it back to stock after an electric fan installation).

Whoever suggested using a flarenut wrench probably never used it on those 10 mm hex fan bolts. Flarenut wrenches with the cutout in order to fit around a tube is built with thick walls by design and will simply not fit the fan bolts with tight access.

Best tool is a 6 sided box wrench with walls thinned on a grinder (if necessary) to fit.

I didn't have a 6 sided box wrench so I did the next best, grind down a 12 sided box wrench.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Pic of Snap-on Flarenut wrenches. See how thick the walls are?

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked