Toyota HZJ75 Troopy Aisin Viscous Fan Hub Part Number

You may find that the one fitted to the Toyota is a "captive part" in that Mr Toyota, in his wisdom got Aisin to build him 100,000 or whatever viscous hubs with some small (or large) difference to what Aisin make for other car manufacturers and only supplied them to Toyota.

You know of course that these hubs can be re-filled with the silicon fluid. Don't know where the stuff goes but if fluid is lost the hub loses it's ability to perform and most times new fluid gets them going like new. The fluid is available from Toyota and maybe from Aisin.

Cheers
Pop

youcan buy aftermaket ones for $90

So more phone calls to Toyota... and the part# this time is 16210-17021 (Aisin FCT016) for my VIN.

The 16210-17020 was deprecated for the 16210-17021 sometime between 1994 and 1999 (still for the 1HZ engine though) .... and now is $695!!


The reason I want genuine (or Aisin) is that they are servicable and tunable.
The last 2 cheap ones have failed with the annoying habit of working around town OK but any load (ie over 90kph or headwind or hill or loaded up) worked intermitantly causing overheating.


For the time being I have overfilled the hub that is on the truck. So its engaged all the time - but its not overheating any more.

good chance its actually your radiator thats stuffed not the fan

Not the radiator - new one in now.

Initially it presented as an intermittent stopping of the air-con, only at highway speed, when it was hot. Gauge would sit about halfway then spike to overheat and drop back again – first thought was a sticky thermostat – so that got replaced. Then a full coolant flush. The viscous hub got swapped with another one (2nd hand) and no change. Then the Aircon was serviced. Ended up with a new radiator. First trip out fully loaded and hot day started overheating with the temp gauge bouncing around from waaaay past hot to the mid point when I backed off. Next in line was radiator cap, new hoses, sender unit and then head gasket… so I bought some silicon fluid to fill my original hub and in the process realised it was shot – I over filled it and swapped out the spare hub. Inspection of them both showed that my original one was the better of the two.

The way they failed is where the bimetal strip attaches to the valve actuator shaft – over time, the slot in the actuator shaft expands and the bimetal strip wears inside the slot. When the temp increases the bi metal strip starts to turn but there is now space in the slot so the valve doesn’t open at the correct temp. In one of mine it didn’t move even with boiling water poured over it – it took a heat gun to get it to open (max of 600c).
So without the valve open the fluid doesn’t get forced into the chamber and the hub is effectively partly engaged (like it should be when its cold) – except when the car overheats it suddenly releases the valve and the fan starts to work properly – the temp drops very quickly – until the valve closes again.

I over filled the hub with fluid (so the valve not opening makes no difference) and the fan is engaged even when cold – no more overheating! But not so good for fuel economy.

When I can find somewhere to host it I'll add the pic to show what I mean.