Visco clutch

[fah320]

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]

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]

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.