Viscous Fan Clutch Question

[Superbracey]

How free-spinning should the viscous fan clutch be in my 940 DTIC?

About 12 months ago after replacing the fan belt I began to notice that the coolant fan was quite noisy even from cold.

There is a lot of resistance when I try to spin the fan by hand when the engine is cold and turned off and at higher revs it sounds like a Hoover.

Some YouTube videos suggest that you should be able to stop the fan from spinning using a rolled up newspaper when the engine is cold. On mine it would shred the newspaper and not stop the fan. Other YouTube videos (other car brands) show that the fan barely spins at all when cold.

I've bought a new fan clutch but I've opened the box and there feels like a lot of resistance when I try to spin it by hand. I don't want to replace mine if its working correctly.

The car gets up to temperature ok and never overheats.

[Ian21401]

My 1992 940 has a viscous fan. I've had the car from 2005 (102,00o miles to the present (210,000 miles.) The temp gauge has always risen to exactly halfway whatever the weather so I expect that it is doing what it's designed to do. A couple of winters ago we were gridlocked in Oxfordshire following a snow storm. We had to keep the engine running to stay warm but the engine just kept running without any trace of overheating and when we eventually managed to motor on again the temp. gauge just sat there on half way.
I think I first encountered the viscous fan on a 240 saloon in the early 70's provided by my then employer and seem to recall being advised that, yes, it was safe to stop the fan whilst the engine was running. I never actually tried that. I seem to remember also being told that a quick test of the coupling was, with the engine stopped, give the fan a firm spin by hand and it should revolve about one to one and a half revolutions.
My fan does provide the characteristic "whoosh" for a minute or two just after start up.

[Clan]

Originally Posted by Superbracey

How free-spinning should the viscous fan clutch be in my 940 DTIC?

About 12 months ago after replacing the fan belt I began to notice that the coolant fan was quite noisy even from cold.

There is a lot of resistance when I try to spin the fan by hand when the engine is cold and turned off and at higher revs it sounds like a Hoover.

Some YouTube videos suggest that you should be able to stop the fan from spinning using a rolled up newspaper when the engine is cold. On mine it would shred the newspaper and not stop the fan. Other YouTube videos (other car brands) show that the fan barely spins at all when cold.

I've bought a new fan clutch but I've opened the box and there feels like a lot of resistance when I try to spin it by hand. I don't want to replace mine if its working correctly.

The car gets up to temperature ok and never overheats.

when starting from cold the fan should drive and make a whoosh noise for a minute or so , the fluid inside heats up due to friction and the clutch then lets go and the fan freewheels around not doing much , if the radiator gets too hot , the hot air heats up the bi-metal coil on the front of the fan this turns the shaft and engages the fan to blow a lot of air for a short time until the air cools down then the clutch lets go and the fan idles around again ...

If yours is whooshing all the time the thing is seized , this will sap a huge amount of power from the engine over 3000 rpm and make a racket and consume a lot more fuel .
These should still be available from Volvo Parts

[ThePurplePanther]

As above, it should get a little free-er when warm then engage when hot.

I'd see how hard it is to turn when stone cold, take it for a drive to get it up to operating temp and see if it feels noticably free-er (i'm going to make it a word!) when the engine is stopped just after driving.

Mine was knackered so was always stiff to turn, went to e-fan and the difference in warm up time and acceleration higher up the rev range was noticable - it effectivly makes the flywheel heavier since it can't freewheel.

They apparently can be disasembled, cleaned and rebuild - or buy a new one (std or 'tropical' if you want the extra cooling). Can't comment of how much difference a working clutch would make compared to e-fan though.

[GreenBrick]

Keep the bi-metal strip/coil rust free it can do its job properly, or it rusts onto itself and the fan stays on.