The Burger Bag Fan Clutch Test
 

91 300 TE cruises at 80C on the meter, after replacing 192F stat with a 180F stat (alternative temp from Rock Auto). I live in the Savannah area where quite hot and slow traffic, so I like to stay a bit cooler.

Pix shows cruise temp at 57 F outdoors. Other pix shows temp at idle after 5 minutes, closing in on 100C.

Took rolled up bag recently obtained from drive thru where temp rise was noticed, and gently touched to fan. Made a noise like cardboard against bicycle spokes. Fan promptly stopped. Would have expected fan clutch to have enough torque to shred paper.

Radiator fins appear clear of trash.

So time for new clutch. This one is low on fluid.

BTW do not try work glove on hand to grab the fan blade. It might have enough torque left to make your nickname "Stubby".

I looked for that test method in the FSM, couldn't find one. How much NM of force was applied by the paper bag to the moving fan?

Yep, its toast. The fan clutch provides most of the lower RPM cooling. Don't get a trashy brand or enjoy replacing it again, along with your radiator and auxilary equipment when it shears off. Send the clip to Michael Bay because he'll use it with the destruction it will do ;)

Once you get it fixed, go back to the 87C tstat..its not the best choice long-term.

re: How much NM of force was applied by the paper bag to the moving fan?
The important factor is zero kNm, or Knuckle-meters. Did not even shred the paper bag.

What is considered a reasonable brand of clutch? Beck/Arnley? I know to avoid Uro if possible. Also learned that bone yard clutches unless new are not a good deal.

Have the previous stat and will put it back once clutch is done, radiator is proved good, some 134a added to the AC, and the list keeps growing.

Does your car have a viscous cooling fan fitted? I'm surprised - mine is an electromagnetic affair ('92 W201).

Beck/Arnley is trash...about as good as URO. They are just chinese reboxers. Behr, Laso or Genuine MB.

Also you don't avoid URO if possible...you avoid URO TOTALLY!!!!!

So, may we also call you "East of Egypt" ?
 

Your Fan Clutch is repairable DIY

http://www.peachparts.com/shopforum/diesel-discussion/195595-refill-viscous-fan-clutch-pictures.html

http://www.peachparts.com/shopforum/diesel-discussion/189747-viscous-fan-oil-viscocity.html

M102s (when they went serpentine, 85+?) and OM601s (I've had 2 85s and my 87 200TD, not sure about the 84s) have the electromagnetic affair. M103s, OM602s, and OM603s still have viscous fans through their whole run as far as I know. Pretty sure M104 and OM606 do as well.

the cooling fan test is pretty simple, you rev the engine, it will definitely let you know its working. It will blow an awful lot of air and will be loud doing it. (garbage truck sound)

you can refill it - but there is no scientific way to tell you how much. And the only test is to either install it on the engine or make up a test rig and spin it up. Too much trial and testing.

I have narrowed it down to 5cc at max as a good starting point and use 10,000 cst oil from an RC hobby store - aka 7000 wt.

The Behr clutch I installed on the 300SEL was crap, it was always locked. Sent it back, went with a Sachs (work great on my E23s)...now it works as designed on the M103.

Yes it is twice the money, but I am starting to think Behr are made you know where now...

OK thanks!

Follow up - old clutch and fan were marked with junk yard crayon, so it had served two vehicles. The Beck clutch came in a box that said Hamburg Parts; at least it sounds German. So far so good.

At the LKQ boneyard in Garden City GA, I saw a SL600 convertible today, body straight. What possessed some one to send a V-12 to the crusher is beyond me. Certainly the highest MSRP of any car on the lot.