Outer Limits 4x4 Board

my viscous fan hub on my tb42 GQ engages to soon and turns off to cold
The fan engages as the engine temp reaches 82deg but then will not disengage until it cools the engine to 75 deg. normal running temp is 80-82 and it can maintain this temp with no fan on at all.
if i could adjust the on temp to around 85-87 and then off at 80-82 it would be a lot quieter and save a little power at the same time

i had one on my toyota an you could adjust it by adjusting the metallic strips from two screws. an you can also use thinner or thicker silicone oil inside the actual viscous hub but im not sure i think if you go thinner it should kick the fan in later???

the ammount of oil in it will set the temperature

The amount of oil doesnt set the temp as i ahve filled mine right up and it engages at the same temp!! It just makes the resistance between the 2 sides of the hub a lot higher so it now pulls a lot more air through.

the only way to adjust the clutch fan is to tamper with the coiled spring on the front of it , it will need to be adjusted so it closes a little later , the pin in the middle of the spring rotates to open and close a valve inside the hub , when the spring is cold the pin is set to have the valve open so the fluid can circulate around the hub ( the hub free spins ) when the spring is hot it rotates the pin to close the valve so the fluid cant circulate around the hub ( the hub is locked )

so although it can be tampered with it is very hard to get right and easy to stuff the hub if not very carefull

i would first check the spring for any mud , rust etc as this may make the spring stick

if you want to have your motor run warmer it is easier to mod your thermostat , get your thermostat and pull it open to expose the pin in the middle the end of the pin that you can see is what you want to mod , you grind off about 2 mm of the visable end and put it back together , the thermostat should now open and close a bit hotter

it sounds like your thermostat doesnt open at 82 deg , it opens and closes at 74 deg and your fan cuts in at 82 to 84 deg but it wont disengauge till the thermostat closes stopping the water flow thus allowing cold air through the radiator to cool the spring on the hub

i did this mod to my thermostat as i was having overheating issues going up long big hills and the guage would reach over 3/4, before the mod my guage sat on 1/3 rising and falling depending on load , after the mod it sits on 1/2 only rising a tiny bit under load then the fan kicks in bringing the temp to a bit under half then it cuts out again , around town the fan doesnt cut in very often at all , only when the a/c is on , and on big hills it only ever gets to a tiny bit over half

i hope i havnt confused you

So much different advice on here...

I imagine most of these would be the same, but on my Hilux (Yes I know different vehicle),

Pulled the hub apart, cleaned out (petrol).
Loosen the two screws, and there should be a natural tension on it (spring loaded). Whichever side it turns is the colder side.

Now, pop it in some water without letting crucial bits get burned and with a thermometer find the temperature that you want it at. Bit of guess work but you'll get there. Find out the thickest fluid you can chuck in there and pop that in and she'll be right!!

(its aford not a nissan) you havent confused me i will try the thermostat cutting as they are cheap compaired to fan hubs
My temp gauge is moving around the same as you described yours was doing before you modded it.
Thanks for the thoughts eneryone I will post results soon