Disassembling viscous fan

[Rob]

Might be of some interest (ignore the bit about idling, its the 2nd half of the answer you want)

http://autorepair.about.com/library/a/1f/bl693f.htm

[MattF]

If I interpreted that correctly, it was literally saying the fan kicks
in/out at lower revolutions, whilst being generally limited at higher
revs. Which comes back to the point. The engine is running hotter
at higher revs, yet the mechanical cooling system is being rate
limited. Thereby, the manufacturers are relying on through flow of
air at higher speeds due to the movement of the vehicle. That still
appears to be a skewed, and ineffective, logic.

[BUSHWHACKER]

Well mine is locked and is staying locked, so there!

[Tallyman]

I'm going back quite a few years now but I believe I was told that the point of the viscous fan is that at higher engine speeds it "freewheels" when there is sufficient air flowing through the radiator to keep everything cool and also cutting down on the extra power needed to keep it running fast, but that when it heats up the oil in the fan causes it to lock up, thereby increasing the fan speed and so drawing in more air to cool the engine. But mind, I could be wrong as it was probably 25 years ago that I leant that.

[MattF]

Well mine is locked and is staying locked, so there!

Mine too.

[MattF]

I'm going back quite a few years now but I believe I was told that the point of the viscous fan is that at higher engine speeds it "freewheels" when there is sufficient air flowing through the radiator to keep everything cool and also cutting down on the extra power needed to keep it running fast, but that when it heats up the oil in the fan causes it to lock up, thereby increasing the fan speed and so drawing in more air to cool the engine. But mind, I could be wrong as it was probably 25 years ago that I leant that.

That does appear to be how it works. However, I personally think
that the flow of air whilst the vehicle is moving isn't enough to
properly cool the engine. Since this warmer weather has arrived,
I've heard the electric fan kicking in far more frequently. It shouldn't
have to. The mechanical one should be ample to cope on it's own.
That's why I've locked mine. I stick to the thought that the electric
fan is there as a last resort backup. If it's kicking in rather often,
other parts of the cooling system ain't working as well as they could.
Hence the locking. I would much rather lose a bit on MPG and know
that the engine is being kept cool and happy.

[BUSHWHACKER]

My mpg went out the window as soon as I fitted mud tyres!

[MattF]

My mpg went out the window as soon as I fitted mud tyres!

My MPG expectations disappeared about two days after getting the
beast. Miles Per Gallon became more like Metres Per Gallon.
The muds do look the dogs nads, don't they. They turn a butch
looking 2nd gen into a sadistic looking beast.

[POPEYE]

Oh god, I've just realised who I'm becoming like with all this needless
bling.

Ear Ear i hope you dont mean me, My bling is nessisiary, Voices told me to do it,

[POPEYE]

OK i've been following this thread and now i really dont know what to do!!
lock it or not?, I certainly want to help her cool down a bit and after looking
a pr@tt by saying i'd like to fit a switch so i could turn the viscious fan on/off
i'm afraid of asking now!! If i got it right is the electric fan supply on the sensor at the front of the stat houseing and by fitting a switch in that supply i would be able to switch it on??,
I'm also think of fitting these on the bonnet with two comp fans on each one
(pushing out), Yes there pretty big measureing about 12x7" (bus roof vents)
Sat em on the bonnet and i think they'll look ok, I know i'' pi$$ the person off who dose'nt like big things on the bonnet and im gonna phone round and see how much to get em chromed so there! If yer gonna hav a vent hav a big one, be bold and make a statement darlings,
As for locking the fan!! does it make a difference? I remember seeing on an assie site where a fan disintergrated and made quite a mess, Dont need that!
Ian
























9

[MattF]

Don't worry, I wasn't meaning you. It's the sensor with the big plug
at the front of the housing for the electric fan. Just making that sensor
wire go O/C will operate the fan. I saw one with the exploding fan blades.
If I remember rirghtly, though, the one I saw hadn't been locked. It had
done that on a bog standard fan. Not sure if it was on a Tacoma? (or
whatever they are called).

Those are vicious looking vents.

[BUSHWHACKER]

It's the sensor with the big plug
at the front of the housing for the electric fan. Just making that sensor
wire go O/C will operate the fan.

Mine doesn't do that, but it does come on if I've been thrashing the nuts off the truck up the huills round here.

[POPEYE]

Don't worry, I wasn't meaning you. It's the sensor with the big plug
at the front of the housing for the electric fan. Just making that sensor
wire go O/C will operate the fan. I saw one with the exploding fan blades.
If I remember rirghtly, though, the one I saw hadn't been locked. It had
done that on a bog standard fan. Not sure if it was on a Tacoma? (or
whatever they are called).

Those are vicious looking vents.

I'm thick so O/C? is that to ground? or makeing the two wires together? Is the feed to this fan constant? (battery) (so the fan can opperate after the engine's stopped and ign off? Come to think of it i dont think i've ever heard the fan cut in, maybe a prob, Frightened of pokeing about with it in case i blow a fuse and i dont know where it is,
I think i'll see how switching the fan and the vents affect the heat before i start messing with the viscious fan, Cheers Matt

[MattF]

I'm thick so O/C? is that to ground? or makeing the two wires together? Is the feed to this fan constant? (battery) (so the fan can opperate after the engine's stopped and ign off? Come to think of it i dont think i've ever heard the fan cut in, maybe a prob, Frightened of pokeing about with it in case i blow a fuse and i dont know where it is,
I think i'll see how switching the fan and the vents affect the heat before i start messing with the viscious fan, Cheers Matt

Sorry. Open circuit. Disconnect that sensor and the fan will kick in.
Easiest way to check if the fan is working is to unplug the connector
from the sensor. Fan should then kick in. No idea as to what type of
feed/switching arrangement it uses as of yet. Been meaning to check
it out, but haven't got round to it yet.

[MattF]

Mine doesn't do that, but it does come on if I've been thrashing the nuts off the truck up the huills round here.

Hopefully I'll need to thrash mine now before that fan kicks in.
Recently, just with normal driving around, it's been kicking in
quite often. Heard the electric fan more within the last month
than since I first got her.