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Discussion Starter #1
Hi,
I have a 94 E200 Auto petrol. Im just wondering should I hear the fan at the front of the engine start up when stopped in traffic? Do engines with auto boxes run hotter than manuals? Ive checked the coolant and its fine but have noticed one or two fuses missing in the fuse box

Cheers

Ger
 

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your cooling fan is engaged by a thermostate controlled switch, at a determined temprature, and then is dissengaged by the same switch, ifyou start you cold engine, your cooling fan will not imediatly run. if your suspicous of your cooling fan, begin with the switch this can be tested easily. are you experiencing overheating problems? if so describe your symtoms. cooling system issues can stem from many roots
 

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Discussion Starter #3
thanks for that, im getting the fan replaced this weekend, its the viscous type, there is nothing more frustrating than sitting in traffic with the engine temp going up and the fan on hot!

rgds

ger
 

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Discussion Starter #4
i took the car to an auto electrician and he confirmed the fan (viscous) is not working. the fan does turn but at a slow speed, a new one is being fitted tomorrow, do you know will this include a thermostat switch?
 

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A viscous drive fan has absolutely no electrical components.

I just disected the old viscous drive unit from my 88 260E and maybe I'll post some pics.

Basically you have a steel disc inside the viscous drive unit and that disc is driven by the serpentine belt. The disc spins in a chamber that is partially filled with a thick silicone fluid. As the disc spins the silicone fluid sticks to it and causes the viscous drive housing to move. As the housing spins the fluid is flung to the outer circumference of the housing where it has little contact with the disc. Hence there's very little drive power being transmitted to the fan.

The silicone fluid leaks out over the years and very, very little power makes it to the fan. On my 260E I could grab the fan blades of the idling engine with my bare hands and hold the fan while the engine idled. I could even spin the fan backwards as the engine idled. I recommend that you do NOT try this trick at home.

Well the viscous housing also has a bimetal snap element visible on the outside as a band crossing the front of the housing. When hot air passing through the radiator heats the bimetal element sufficiently it moves and operates a plunger under it. This directs the silicone fluid in the chamber back onto the spinning disc where it increases drag (and drives the fan blades more agressively).
 

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Discussion Starter #6
hi, thanks for that, the fan was replaced at the weekend and the car seems to behave itself ever since. the old fan was clogged up with dirt and the bearings were worn out too. thanks for your help

ger
 
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