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Posted: Sun Dec 30, 2007 10:44 pm
by RockyF75
The engine fan.
I don't know exactly how they work but they have a fluid in them and they are designed to be able to 'slip', so, for example if you go through deep water, they won't keep spinning at same revs as engine and cut up your radiator etc.
Posted: Mon Dec 31, 2007 12:47 pm
by Gwagensteve
Correct - we're talking about the main engine driven fan. The hub of the fan is a finned aluminium casting and it's filled with a silicone fluid. The shaft that bolts to the water pump is connected to an impeller inside the hub. There's no mechanical connection between the shaft and the fan blades.
As the fluid in the hub is heated by the hot air passing through the radiator, it gets thicker and that starts driving the fan. As it cools it gets thinner and then the fan slips.
When you drive the car from cold, for 30 seconds or so, you will hear the fan "roaring." As everything gets moving the fan will go quiet as it is freewheeling. As you heat the motor (in sand or on a long hill, or if your'e idling at the lights you'll hear the fan start to roar again.
If you can't hear in roaring, ever, you have a crook fan. I know of people who have spent $$$$ trying to overcome cooling problems that were all due to the stock fan dropping its silicone fluid.
I believe that only toyota sells the fluid over the counter. Once refilled, it might not work exactly as it should, but it will work acceptably. (There are lots and lots of grades of silicone)
Yes, water has a lower boiling point (and higher freezing point) but cools better than glycol.
Steve.
Posted: Tue Jan 01, 2008 12:57 am
by Buggerific
Huh,
Well there ya go!
Might give that one a shot also...
Any ideas of how to find out what grade of silicone i should be using or is it more of a guesstimate?
Posted: Tue Jan 01, 2008 1:12 pm
by MightyMouse
I think Steve's suggestion about using the silicone available from Toyota is about as good as it gets. After all its used for exactly the same purpose so I can't imagine it being too far away from what you need.
I suspect that its also way easier to get from toyota than to go chasing industrial suppliers who probably arn't that interested in selling you a few hundred milliliters.