Viscous Fan check, once and for all...

[tashtego]

Hi everyone

I'm getting my 3rd Gen ready for an overland trip to the Mozambican coast during the Christmas period.
Will be extremely hot and dusty, so I'm going through all sort of cooling system checks and got a bit stuck on the viscous fan.
Would like to do a check on mine to make sure the silicon oil is still there and doing the job.

After reading probably dozens of threads between here and aussie forum I am still confused as often within the same thread some posts totally contradict each other...

How should it spin when hot or cold?

All I know is that when my engine is hot and I switch off, the fan stops dead solid when the engine stops. If I then try to spin it by hand it doesn't free wheel, it only moves if I keep the pressure, if you know what I mean.
Does this mean that it is working fine?

I don't know how the fan spins with the engine cold, but I will tomorrow morning...

Thanks in advance and have a nice weekend.

[wiggy]

Hi everyone

I'm getting my 3rd Gen ready for an overland trip to the Mozambican coast during the Christmas period.
Will be extremely hot and dusty, so I'm going through all sort of cooling system checks and got a bit stuck on the viscous fan.
Would like to do a check on mine to make sure the silicon oil is still there and doing the job.

After reading probably dozens of threads between here and aussie forum I am still confused as often within the same thread some posts totally contradiceach other...

How should it spin when hot or cold?
All I know is that when my engine is hot and I switch off, the fan stops dead solid when the engine stops. If I then try to spin it by hand it doesn't free wheel, it only moves if I keep the pressure, if you know what I mean.
Does this mean that it is working fine?

I don't know how the fan spins with the engine cold, but I will tomorrow morning...

Thanks in advance and have a nice weekend.

No you should feel resistance when the engine is cold but there is an excellent thread about servicing the viscus fan someplace on here, but I think it sounds like its working alright.

Good luck with the trip

Rob

[stormforce]

One way to test the fan is with a rolled up newspaper.Have engine running and after a short while gently put the end of the newspaper onto the fan blades.The blades should shred the end of the paper if working ok.You will need a silicon based oil if you do refurb it.Like Rob said do a search for Viscous Fan and there's a full write up on how to do it

[ST185pinjo]

I found this the other day, maybe it will help you.

http://neuralfibre.com/paul/4wd/tuni...ous-fan-clutch

Have a nice trip! Interested in how you prepared the car for the trip. Can I find it on here?

[tashtego]

STORMY, WIGGY

Thanks chaps, I am still quite confused by the contradicting info found online. The more I read the more confused I get. When the engine is stone cold in the morning, should the fan spin freely? And when it's hot, and then the engine is switched off, should it be stiffer, so that it doesn't really spin if you flick it? Some posts say this is how it should be. Others say the exact opposite...
At this stage I am still trying to work out if it's doing what it should or if I need to do the silicon oil refurb.

JEF

Thanks for your link, way too technical for me but very detailed and interesting.
I will post a thread on how I prepare the 3rd Gen for overlanding if you're interested.

Cheers

[stormforce]

http://www.hiluxsurf.co.uk/showthrea...hlight=viscous

This is the thread from MattF a few years ago.This will be what you need to know.MattF spent alot of time on his truck

[tashtego]

Thank you Stormy, very useful link should I need to open up the unit and refill.

I am hoping it's actually working ok so I won't need to.

Cheers

[stormforce]

Yea you open it up and refill.I think it gives the right spec of oil in that thread somewhere

[ST185pinjo]

Thanks for your link, way too technical for me but very detailed and interesting.
I will post a thread on how I prepare the 3rd Gen for overlanding if you're interested.

But it has pics...
I would love to see it.

[tashtego]

Sure, but my surf is nothing special, no fancy mods, bit of a working vehicle I am afraid...

[Overland Tonka]

Heard a few stories about replacing the oil..not all good ones. Having now bought a new viscous fan from Toyota and seen the difference from my so-called modded one i would never do this mod again...just my experience, not others who are happy with the mod.

Oh, and Tash..don't forget the pics of the trip..

[tashtego]

Hi Tonka,

Sure, I will try to take some good pics now I've got a fancy new phone...

Good to hear that now you have got a new unit you are running that much cooler.

I have now checked the fan this morning, before starting the engine. It was as stiff as last night, when it was hot. You couldn't flick it basically.
Then I started the car and let the engine run for 5 mins, then switched off. Flicked the fan blades again and this time the fan was pretty much freewheeling.

I have since found this excellent link:

http://silvertonrads.co.za/technical...diagnose-them/

It explains that when the engine is stone cold the clutches will be in the same state of engagement as they were when the engine was shut down.
Hence the stiffness before starting the engine.
Then as the engine warms up slightly the clutches decouple and the fan become freer.

Only to then lock up again when the engine is properly hot and idling or travelling at low speed.

This could explain why on so many different forums folks come up with exact opposite advice, some say it should be stiff when cold, some say it should be freewheeling when cold.
In a way they are both right!

I'd really encourage people to have a look at this link,if they have doubts as to whether their viscous fan is working ok. It's quite clear even for numpties like me.

So I'm hoping my fan is doing ok.

My truck does a lot of miles, it's already got 148000 km on the clock (and probably not even genuine mileage), and it is not getting any younger. Since I do long trips in crazy heat I'm getting a bit worried about cooling...




Cheers

[floatingkiwi]

What happens when the engine is stone cold is that all the oil in the hub flows to the bottom of the vanes and tends to lock the hub up overnight/whatever. After starting, the rotation allow the vanes to pump the oil back through the valves into the reservoir of the hub. Then when it gets too hot, the bimetallic valve closes off the valve and the oil that is being pumped around by the vanes has nowhere to go and serves to lock up the hub.

Try going out in the morning before you start up and turn it by hand. The hub will be hard to turn first off. Start to turn it (in the correct direction which is actually opposite to what you think. When the pulley turns clockwise the fan lags that and results in a continual anticlockwise motion at the hub) and after a few revolutions you'll feel it start to loosen up.
So, when it is dead cold it should be stiff, then it goes loose just after startup, then again stiff when it gets too hot.

[tashtego]

Exactly.
Thanks for that. When I first looked around I found a lot of info, even on here, saying it should be easy to spin when cold, which kind of threw me.
Cheers