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Old 05-26-2003, 04:09 AM
Greg in Oz Greg in Oz is offline
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Join Date: Jan 2003
Location: Sydney, Australia
Posts: 627
Viscous coupled fan for M102 possibility?

As an owner of cars powered by the M102 and M103 I can say how superior the viscous coupled engine cooling fan on the M103 is to the electric clutch coupled fan on the M102. On the M103 the viscous coupled fan engages when required as the temperature rises, shifts sufficient air to maintain the correct temperature at idle and is speed limited so as not to get out of hand at high engine speeds. Regardless of driving conditions the M103 maintains a stable temperature.

The M102 on the other hand, maintains a stable temperature on the move but when stopped in traffic at higher ambient temperatures, the engine temperature begins to rise. At around 100 C the clutch engages the fan but at idle it struggles to control the temperature. When the trafic moves and you accelerate the fan roars as there is no viscous clutch to limit its speed. Its drag on the engine can be felt as it consumes large amounts of power, now rapidly puling the temperature down. With the direct coupled electric clutch the fan is a compromise that shifts insufficient air at idle and excessive air at high engine speeds. Surely, the resulting temperature cycles between about 85 and 105 degrees C cannot be good for the engine either.

Has anyone ever considered a viscous clutch conversion for the M102? Obviously the M103 fan cannot be used as the direction of rotation is reversed (due to the M103 fan being driven from the back of the belt). Maybe a M111 fan and clutch could be used. Any ideas?

Another possible mod I have considered would be to reverse the roles of the engine fan and auxiliary fan. This would have the electric auxiliary fan switch in first at around 100 C and the engine driven fan only for really hot situations. Not as good as the viscous driven approach but possibly better than the original setup.
107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.
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