New Viscous fan spins freely when warm but less when cold!?

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adies_v8

Active Member
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326
Location
Hampshire
So, troubleshooting the temp issue on the 3.5 we noticed that the viscous unit had the same resistance when the engine was stone cold or boiling hot.

A new viscous has been fitted, no issues with fitting. Fan out the way, rad cover off, Vis’ unit removed easily, fan checked, new Vis’ unit on, shroud back on, fan on with new bolts supplied. Done.

We went to test it, i.e. let it warm up and just see what happens. We turned it off when it went over 3/4 on the LR temp gauge.

Spinning the fan, its stupidly 'free' spinning. it will happily spin for a good 3 to 5 seconds after the fan belt/water pump shaft has stopped spinning. Feeling it by hand, it smoothly can be flicked to spin easily.
The unit itself is on the shaft. Just nipped up to the same feel as the one that came off.

Leaving it to cool, the unit spins less freely, almost to the state the other one felt like before we removed it.

On the instructions it says the unit is shipped in a 'deactivate' state and becomes active after some revolutions, well it did a couple of thousand and no change.
Checked there is no plastic tab (thinking of printer cartridges at this point) but it just seems fine!?

The Viscous unit, no blades, just the chunk of metal was purchased from a trusted source (don’t want to name incase it’s a complete accident the wrong one was given, never happened before so, meh, not bothed about that bit).

am i doing something wrong?
is there something stupidly simple i have missed?

cheers for the input

.adie.
 
just a thought
Is your radiator getting hot all over,The viscous coupling needs the heat off the radiator to work
A bit like an ellec fan not coming in when a engine is hot because the part of the rad the thermo switch is in isn't hot enough
 
There is a storage method for these, they mustn't be stored a certain way up due to movement of the silicon fluid/gel, but other than that I've always had them work with no issues. Same with speedos etc on the dash.

It does rather sound like yours isn't right to me.

Peter
 
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