Thread: Td5 viscous fan coupling stuffed?

The fan hub is usually engaged slightly when stone cold, until the fluid shears and it then begins to freewheel. It should only be engaged for about a KM or so and then not again until the engine reaches operating temp and the ally heatsink then transfers the temp of the rad airflow to the silicon fluid and thenthe fan will lock up again.

JC

just took it for a drive from cold - unfortunately the fan doesn't cut out at all - even after 1 or 2 kms... The car doesn't have any overheating issues (measured independently of dash gauge), and obviously it's more of an issue if the hub isn't locking up at all - should I be concerned about this?

I would get it fixed as it may eventually fail completely,& then overheat the engine

Mine does exactly as JC said.If it was on all the time,you would be able to hear it as they are fairly noisy,particularly noticeable at slow speeds.

Originally Posted by feraldisco

just took it for a drive from cold - unfortunately the fan doesn't cut out at all - even after 1 or 2 kms... The car doesn't have any overheating issues (measured independently of dash gauge), and obviously it's more of an issue if the hub isn't locking up at all - should I be concerned about this?

Hi Feral,

You're not expecting the fan to actually stop turning are you? They are always turning when the engine is running but, as I understand it, when the engine is cool, the hub slips a lot as engine rpm rise and the fan runs a lot slower than the pulley. As the engine gets hotter and the air through the radiator does likewise, the viscous coupling gets warm and 'grips' tighter, so that the fan does run at near the same speed as the pulley.

Now, I don't know how you can tell definitely whether it's all working as is should. Maybe you can compare the noise of the fan when giving the engine a few revs with you head under the bonnet, both when it's been running for a few minutes but still cool and then after it's well warmed-up?

Ian

I had assumed from Justin's response that there would be a noticeable difference between initial start-up, about 1km when it starts freewheeling and then when it engages properly once warm - I can't detect any difference in the fan between start-up, 1km or 50km...and the fan has never been noisy. I doubt this is because it's not engaging properly as I would have thought I would have done a head by now...

Take a house paint brush 50mm or wider on your next trip. After a k stop car leave engine running, slowly apply the bristle end of the brush against the fan blades to apply a braking force. If the fan is coupled/engaged you will not stop it with a brush, if it is slipping ie not engaged due to the temp still cold then you should be able to stop the brush with the drag applied by the bristles. Caution when placing your hands near rotating parts