Viscous Fan Test

[vnx205]

It isn't clear in the posts I have seen about stopping the fan with a paintbrush whether a functional fan is difficult to stop or impossible to stop with a 100mm brush.

[vnx205]

So which is it - difficult or impossible?

[PhilipA]

I would think it would depend on the temperature of the air coming through the radiator as it is the spring on the front of the VC which opens the valves to stiffen it.

If over 94C then I would think impossible to stop under 94C it would be difficult.
So it depends.
IMHO a better test is to take it off and look for fluid leakage around the shaft. Lots of grunge =leaking fluid , nice and clean =probably good.

Regards PhilipA

[dero]

I have done it with a rolled up magazine .
Slowly push it in to the fan blades , eng. hot , if the coupling is U/S you can stop it completely , takes a bit of force , but if it is good you can not stop it .

[dromader driver]

I have done it with a rolled up magazine .
Slowly push it in to the fan blades , eng. hot , if the coupling is U/S you can stop it completely , takes a bit of force , but if it is good you can not stop it .

Agreed with the approach

[DazzaTD5]

Dont be a bunch of pussies, use your fingers [tonguewink]
Or rather than that, try:

*Start vehicle when cold, bring rpms up a bit, listen for fan roar and listen for a bit longer and you should clearly here the fan roar die down.
*Once hot with engine running, place hand behind the fan (while keeping fingers away from it) and feel the amount of air being forced back. A failed fan wont push much air and often you can see that the fan is barely even turning.