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  #16  
Old 10-24-2002, 11:09 PM
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Quote:
Originally posted by psfred
The hotter the rad the greater the heat transfer. Letting the coolant get to 120C before turning the fan on saves fuel and allows greater heat transfer from the engine to the air. No risk to engine.
You go ahead and trust Stuttgart engineering that designed the engine to run at 75F summer temps. I would never continue running my engine if it ever hits that temperature. BTW, why do you think they designed the clutch to lock at so high a temperature when they program the aux fan to cut in at a lower temperature? That means the fan never locks up unless the aux fan has failed in which case you are in overheat country. If the aux fan hasn't failed and your engine is still hot then there is something seriously wrong with the engine. My point with this is that the VFC has a flawed design that even MB's engineers acknowledge.

As for saving gas, Engine management retards ignition timing when the engine gets that hot and sure you'll save gas, but your engine will be sluggish at best. My car is happiest/liveliest between 85C-90C.

But that's just my opinion...
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  #17  
Old 10-24-2002, 11:46 PM
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Visco clutch locks up before the aux fan runs in high speed. Ditto on my 280 SE -- visco clutch locks up at about 95, aux fan at 100C.

These cars are engineered to run anywhwere, not just Germany.

The usual problems with cooling start at about 200,000 miles on average, at which point the radiator is full of crud and needs to be replaced.

Don't short the engineering expertise of MB -- their cars are way ahead of everyone else. Not so true now as it used to be, but still true. Overheating is a maintenance issue, they DON'T over heat when in good condition. 120C is not overheated, and the timing is not retarded when hot, it is advanced to speed the engine up! Knock will retard the engine (use premium, the best you can find, in hot weather for this reason). If the temp gauge sits at the mark above 80C all the time in traffic, your radiator is crudded up or the visco clutch isn't working.

Peter
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  #18  
Old 10-25-2002, 12:51 AM
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I will refer you to this thread regarding the issue of the viscous fan clutch lock-up temp. It may start to activate at a lower temp but it does not lock until coolant temps are >115C.

Quote of Stu Ritter article

Quote:
the timing is not retarded when hot, it is advanced to speed the engine up! Knock will retard the engine
huh?
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  #19  
Old 10-25-2002, 04:51 AM
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Unless MB uses a different knock sensor... knock sensors detect engine pings (not temp). If engine ping is detected, it will retard ignition timing to protect the engine. Take my W124 230E (though not equipped with any knock sensors) as eg, with ignition timing at 15 deg BTDC. When coolant temp remains below 100C (ambient 35C), there's no audible engine pings. Once coolant temp reaches 100C & above, engine ping steps in. When coolant temp reaches 110C to 120C, the engine ping is really very bad... even pings when car is stationary with D selected. My point is, although the knock sensor does not retard ignition timing by measuring temp directly, engine ping is related to engine temp (apart from other factors such as quality of fuel, intake air temp, compression ration, etc.) such that as temp goes up, so does engine pings (hot combustion). Essentially, when temp goes up, ignition timing is RETARDED, not advanced. If its the other way around, you'll be replacing your engine block, pistons, etc. in no time!


Quote:
Originally posted by psfred
Visco clutch locks up before the aux fan runs in high speed. Don't short the engineering expertise of MB -- their cars are way ahead of everyone else. Not so true now as it used to be, but still true. Overheating is a maintenance issue, they DON'T over heat when in good condition. 120C is not overheated, and the timing is not retarded when hot, it is advanced to speed the engine up! Knock will retard the engine (use premium, the best you can find, in hot weather for this reason). If the temp gauge sits at the mark above 80C all the time in traffic, your radiator is crudded up or the visco clutch isn't working.
Peter
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  #20  
Old 10-25-2002, 11:01 PM
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Hmmmm???? Well I am the originator of this post...lots of good info! SO...should I get an electric fan or not?? I am wanting one for 3 reasons. 1) More horsepower (how much can I expect?) 2) Quieter operation (with SPAL curved blade design), so I won't have this loud "whooshing" noise at idle and low speeds, after all, this is a Benz, it's supposed to be quiet right? and 3) it will clean up the engine compartment. Your opinions and comments on these are obviously welcome.

I mean, I got some of what you all said, but what's the "nitty gritty"? It seems that many other W126 and owners of older models have put electric fans on their car with no apparent problems, like the guy from the link on a previous reply on this topic ("electric fans"). So the next question is, "If they can do it, why can't I?"
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  #21  
Old 10-25-2002, 11:22 PM
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there may be an issue with the duration of the fan cycles and its drain on your battery. that was why a previous poster had used the special thermostat to avoid that problem. having the maximum cooling capacity of the radiator available all the time keeps the electric fan from coming on constatly. i don't know if that particular configuration is suitable to all engines or if it was specific to the one engine. someone else had installed electric cooling fans but never reported back on what he did with the thermostat. with the onset of cooler ambient temps, these issues may not be readily apparent and it may not be a good time to do this conversion (your converted system may work ok in the winter but fail miserably in the summer).

i guess the short answer is that the experiences posted by members who have done the conversion are not conclusive enough to provide you with a definitive answer. i suggest you read all the threads that discuss this and make sure you understand all the issues completely before you start...

battery drain?
visco fan replacement (discussion of "negative thermostat")

HTH
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Last edited by jsmith; 10-25-2002 at 11:49 PM.
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  #22  
Old 10-25-2002, 11:39 PM
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Horsepower consumption of the factory fan is minimal when not engaged. You will save some, but I suspect you will not notice it.

The new fan will be quieter than the engine driven on, but you will still hear the air moving, no way to make that any quieter. You will have to be the judge of that.

The fan won't clean the engine compartment any more than driving at 50 mph.

However, there is no real problem. Most newer cars (and cars with transverse engines) don't have engine driven fans anymore. You won't go wrong UNLESS the fan stays on all the time. In that case, you are using more horsepower than the engine driven one.

That all said, there is no real reason not to install one if you want. Just don't screw around with the thermostat system, it works just fine as is, all you are doing is driving air across the rad at slow speeds with an electric fan rather than an engine driven one.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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