Clutch Fan

Dodger if you can here the motor, you should be able to hear the fan when it engages, it should be very loud, especially if you stab the clutch in and give it a hard rev while listening. It should roar!
However in saying that, just because the fan is locking in does not mean it's working properly.
It took many months of convinving before I belived that my fan was not working 100%. It locked in when hot and made heaps of noise and I was convinced it was working fine but I still had overheating probs on long hills on hot days. Put two tube os Toyota silicone stuff into it and hey PRESTO! No problem.

as mentioned in a previos post bit of a black art area and poorly understood. I read on an aftermarket dacon viscous hub asembly box under the how do you know if i am stuffed heading that when you turn your motor off it should perform not more than a couple of rotations. Next time you are experiencing "gauge north situation" quickly pull over pop the bonnet and see what the fan does. I did this and the fan took 5-10 seconds to stop spinning = stuffed It only took a couple of minutes for the fan to stifffen back up. If you read my procedure on adding oil it only took me about 1hr and $20 to fix

i dodger,

with my maverick it all ways run above normal on the temp and when towing my van up to cairns well, i finally had to put a new fan and clutch on up at weipa (not something you want to do , the price ) but since then it only gets up to normal range when towing the van on hills, made a big differance. good luck.
petza

I had problems with mine just before a trip. The vehicle would only overheat on one very long steep hill. Cooling system checked, bits replaced etc but no go. Tried cardboard in front of radiator etc etc and didnt budge. Replacing the unit did the trick, no worries since. When it cuts in I can hear it in my 80 series quite easily.

Dodger
An old mechanics trick to test viscous coupling.
Bring engine up to op temp, get a rolled up newspaper, stand on passenger side of car and slowly insert paper into fan. If paper gets shredded, it's OK. If fan stops then clutch needs servicing/replacing.

Having said that, if you push the car hard while towing with a/c on then the heat from the a/c condensor (in front of radiator) will effect the operating temp to some degree. Especially if it is also a stinking hot day!!

The trick may be to back off on the go pedal a bit

It may also pay to look at thermo fans. I have heard that the 4.2 gets a bit warm when pushed. You should be able to get a thermo fan set-up from a 3.0 patrol at da wreckers, cos we all know that wreckers yards are full of 3.0 patrols, don't we.

Don't snap at me, I drive one !

Cheers,

muzz

Dodger,

Trick I learnt, get under the bonnet, get the engine up to normal operating temp, manually give the revs heaps, looking at the fan sideways as the engine speed increases, the fan should flatten out as it spins faster and the blades flex slightly inward to make the thickness of the fan reduce, reduce engine speed and they shouldflex back. If the fan is working properly, should hold the flexing position continually at higher revs. If not, the blades will not flex at all or flex up to certain degree and then release as the engine speed picks up and viscous lets go.

By the way, from what you said me maybe the engine is not reaching a temperature requiring the fan to kick when you look at it. Someone may be able to refute what I am saying, but if you were to say stick some cardboard right of the front of the radiator and drive a bit, should simulate overheating and give you a chance to check. Listen to the fan under revs at normal temperature, and then at overheating temperature, and check fan movement straight away. Should be a difference if working. Be careful not to overheat the car and blow up your GU 4.2!!!!