The viscous coupling,when its cold turns freely,but I have noticed that when its warmed up it still turns nearly the same,any ideas is it time for a new one,what's the best and cheapest option.Cheers Andy
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noahsmithTags: None
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It shouldn't run freely. It should be full of a thick oil like substance. When the engine revs are low the fan will spin roughly the same speed as the engine. When the revs are high the friction of the fluid with the internals of the coupling will slow the fan down, theoretically saving a few HP.
If your fan is spinning freely then the coupling isn't doing its job and your cooling system will be comprimised. Not good in this weather! Replacements can often be of poor quality so if you replace it, buy it from a supplier that you are confident will honour their warrantee and replace it if it packs up. The one on my car was knackered when I bought it so I replaceed it. I have replaced it twice since then and I have only had the car a year and a half! Current one is from LD Part and holding strong!
Regards
Dave
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StagnJag wrote:It shouldn't run freely. It should be full of a thick oil like substance. When the engine revs are low the fan will spin roughly the same speed as the engine. When the revs are high the friction of the fluid with the internals of the coupling will slow the fan down, theoretically saving a few HP.
If your fan is spinning freely then the coupling isn't doing its job and your cooling system will be comprimised. Not good in this weather! Replacements can often be of poor quality so if you replace it, buy it from a supplier that you are confident will honour their warrantee and replace it if it packs up. The one on my car was knackered when I bought it so I replaceed it. I have replaced it twice since then and I have only had the car a year and a half! Current one is from LD Part and holding strong!
Regards
Dave
the principle behind the coupling is that the fluid inside thickens with temperature - when the engine is cold you don't want to drive the fan hard or at high speed, so thin fluid and it slips..... the finning on the coupling is there to take in heat, not disperse it - so when the heat coming off the radiator and through the body of the coupling from the engine reaches a certain point, it thickens up, drags the fan around harder, and cools the rad down..... as the air coming off the rad cools due to the water temp coming down in theory so does the coupling fluid and slip commences again.
You should really be checking coupling resistance when the engine is hot....
Russ:dude:
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