Visco clutch

fah320

Member
Joined
Nov 5, 2010
Messages
54
Location
Bursa/Turkey
Car
2001 E320 CDI
Whenever I start the car fan engages for about a minute then disangages. I hear the engine roaring loudly till 2000 rpm in the morning with a cold start and if I park the car and stop the engine with running temparature and start it again after sometime. Is this normal???
 

grober

MB Master
Joined
Jun 22, 2003
Messages
29,943
Location
Perth, Scotland
Car
W204 ESTATE
The viscous fan is controlled by a bimetal strip in the centre-this acts on a pin which then allows the silicon fluid into certain galleries to "couple " up the fan. This should "decouple" when the bimetal spring cools. The bimetal strip is positioned to sense the temperature of the air flowing through the radiator and as the coolant temperature increases then the coupling should act at a predetermined temperature range to provide extra engine cooling. the bimetal strip can get clogged with road dirt and the pin can get sticky. Try giving the assembly a gentle clean with something like WD40 and an old toothbrush. If that doesn't work you may have to renew the coupling.
 

krimat2005

Active Member
Joined
May 31, 2009
Messages
319
Location
Littlehampton, West Sussex
Car
Mercedes W124 300D/ S203 220cdi
it's ok viscous will stay engaged for few minutes after start up (cold or hot), it's because fluid needs time to spread inside coupling.
 

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