Hi all,
Just found this description of how the fan works, not sure how correct it is (if not can a moderator pls dispose of this post) Thought this may be good reading for some people. Doesn't blow ya mind either.
To check if your viscous fan hub is OK you have to do it when the engine is cold eg. first thing in the morning.
With the bonnet up start the engine and you should hear the fan "roaring" (sucking air through the radiator) for about 5 - 10 seconds or so and then settle down to no noise at all. If you don't hear the roaring noise on start-up the fan hub is probably stuffed!
The reason for this is that at cold start-up the silicon oil (or whatever it is) in the fan hub has settled to the bottom of the hub over-night and forms a thick "grippy" mass in one spot. This causes a few seconds of sucking air ("roaring"), after start-up, until the "oil" is flung to the outside edge of the hub, the hub starts to slip, and the sucking stops. (centrifical force)
When the fan hub gets to operating temperature i.e. hot engine, metal expansion in the hub causes the "grippy" thing to happen again and the fan starts to suck air through the radiator with the same "roaring" noise as when it was cold.
You can't just spin the fan by hand and see if it spins freely or not to check if it is OK or U/S.
RYAN
Just found this description of how the fan works, not sure how correct it is (if not can a moderator pls dispose of this post) Thought this may be good reading for some people. Doesn't blow ya mind either.
To check if your viscous fan hub is OK you have to do it when the engine is cold eg. first thing in the morning.
With the bonnet up start the engine and you should hear the fan "roaring" (sucking air through the radiator) for about 5 - 10 seconds or so and then settle down to no noise at all. If you don't hear the roaring noise on start-up the fan hub is probably stuffed!
The reason for this is that at cold start-up the silicon oil (or whatever it is) in the fan hub has settled to the bottom of the hub over-night and forms a thick "grippy" mass in one spot. This causes a few seconds of sucking air ("roaring"), after start-up, until the "oil" is flung to the outside edge of the hub, the hub starts to slip, and the sucking stops. (centrifical force)
When the fan hub gets to operating temperature i.e. hot engine, metal expansion in the hub causes the "grippy" thing to happen again and the fan starts to suck air through the radiator with the same "roaring" noise as when it was cold.
You can't just spin the fan by hand and see if it spins freely or not to check if it is OK or U/S.
RYAN
