Radiator fan hub working or not

[fender22]

I recently was going up Toowoomba range with a heavy trailer on the back
and for the first time ever my 94 TDI 200 started getting hot.
It was suggested to me probably the hydraulic cooling fan not cutting in as I have replaced the radiator and hoses in the last couple of years.
Anyway, got a local price of about $200 and picked one up (new) in Sydney online for about $100. I assume a generic brand. The mechanic fitted it and was a bit concerned after driving it (in cool winter weather) for 30 minutes the fan still felt like it was free wheeling. Has anyone had much experience with these?
Do they only stiffen up and kick in really hot weather or should it be kicking in under normal conditions when the engine comes up to temp?

[Spudlynicholas]

From the Toyota Surf forums I used to follow (The Tojo's are notorious for getting hot under load) it seems the cheaper viscous fans are not very good.

I'm not sure if it's a similar issue here with a different make, but I'm thinking it could be.

Do you hear the fan 'roar' when the the engine is revved when hot?

[fender22]

You're probably right re the cheaper fans. I don't know. Am kicking myself a bit now for going cheap. Having said that, when you ask me if I hear the roar when the engine is "hot" I have never heard that in 5 years. I had it done a week or so ago and its winter now and even after a 1 hour drive I doubt you could say it was "hot". Infact most times I reckon after even a long drive you could put your hand comfortably on the tappit cover. Might be a different story on a hot summer day in traffic or under load. If "hot" means normal working temperature I haven't heard that roar. Not sure when these things are sposed to kick in? Maybe if the temperature started climbing past normal it will kick in?

[rover-56]

The activation temp is about 95-110c at the fan hub, and you should hear a roar for a few seconds at cold startup until the oil is redistributed around the hub. If your cooling system is ok you may never hear it engage. I certainly know when my D2 one engages - slow climb in low range in summer with an auto. Makes a lot of noise.:)
Terry

[Yorkshire_Jon]

How hot is 'getting hot'? How many Km's?

Many diagnose the viscous unit as failed the first time the engine gets abnormally hot when infact the head gasket has let go between the back two cylinders.

Not trying to worry or jump to concussions but I have replaced many 200tdi head gaskets when I was in the UK for this very reason.

Head gasket failure interval on a 200tdi in the UK was reliably 100,000 - 120,000 miles. Swapping the gasket is pretty quick and easy if you get in there and catch it early.

Chances are there will be no other tell tale signs...

If you go this route, new head bolts.

[Gerokent]

Easy to check for correct operation is drive your car until it's hot (hot), then with a rolled up newspaper try to stop the fan spinning. If you can stop it, it's buggered. (nothing a couple of self tappers cant fix:))