Hi I’ve been trying to figure out if the fan hub on my d22 2008 is faulty . Everything I’ve read on them says that the blade should be free spinning when cold and stiffen up when hot. I tested it the other day and it’s the complete opposite. It’s hard to turn when the motors cold and when fully warmed up it spins easy . How is this possible . It doesn’t ever overheat but does take ages to warm up.
Viscous fan hub
- Thread starter Newnav100
- Start date
Help Support Nissan Navara Forum:
The way you describe that it ought to be is how it's supposed to work. The idea is that when the engine is cold, the fan doesn't have to work hard because the engine's cooler than it needs to be, but when the engine is warm, the fan has to work harder so its grip on the shaft driving it becomes firmer.
The trick to knowing whether or not your fan is ok is easy, and only requires one other person who knows how to turn the ignition off.
With a hot (normal operating temperature) engine, stop and pop the bonnet. Watch the fan carefully as your assistant turns off the motor.
If the fan stops at the same time as the engine: the fan and clutch are good.
If the fan runs on for a few revolutions after the shaft has stopped spinning: the silicone oil inside has either drained, worn or in some way isn't performing as well as it needs to. I've encounted this with my D40, and I opened my viscous hub up and added a bottle of silicone oil that I bought from a Toyota dealer ($18 ). This fixed it so well, I haven't had any problems in the last 100,000km.
The trick to knowing whether or not your fan is ok is easy, and only requires one other person who knows how to turn the ignition off.
With a hot (normal operating temperature) engine, stop and pop the bonnet. Watch the fan carefully as your assistant turns off the motor.
If the fan stops at the same time as the engine: the fan and clutch are good.
If the fan runs on for a few revolutions after the shaft has stopped spinning: the silicone oil inside has either drained, worn or in some way isn't performing as well as it needs to. I've encounted this with my D40, and I opened my viscous hub up and added a bottle of silicone oil that I bought from a Toyota dealer ($18 ). This fixed it so well, I haven't had any problems in the last 100,000km.
Thanks tony I’ll give that a go
the fan should spin a bit when engine stops, it should not keep spinning. if it keeps spinning it means there is no silicone in there.
what they meant by being stiffer when hot is when its super hot and the thermostat on the fan has kicked in and made the fan pump more silicone around to drive the fan more. but your not going to see that unless your driving up a hill. so its a crap way to test.
engine taking ages to warm up is often jammed open thermostat or how your driving. diesels need load to be able to heat up, driving uphill or at highway speeds is good. flat and around town speeds will take ages.
what they meant by being stiffer when hot is when its super hot and the thermostat on the fan has kicked in and made the fan pump more silicone around to drive the fan more. but your not going to see that unless your driving up a hill. so its a crap way to test.
engine taking ages to warm up is often jammed open thermostat or how your driving. diesels need load to be able to heat up, driving uphill or at highway speeds is good. flat and around town speeds will take ages.
Just so long as the hub isn't tested by shoving a rolled-up newspaper into the running fan ...
The fan should be stiff when it's cold, because the cold oil has settled to the bottom of the hub, just listen to any Nissan with a viscous fan taking off from cold, sounds like it's revving its' ring out because the fan's locked up, frees up a bit and settles down when the oil starts moving around.
Look for oil seepage on the shaft at the back of the hub, that's your best indicator that there's a problem.
Look for oil seepage on the shaft at the back of the hub, that's your best indicator that there's a problem.
It just seems backwards to me . Shouldn’t it free spin when cold to let the motor warm up? And then stiffen up once the radiator needs cooling?
Only takes about 100 metres to spread the oil around the hub, and then it will spin freely, 'til it gets hot. I'm talking cold, from sitting overnight!
Go out one morning, lift the bonnet, if the fan is hard to turn, leave the bonnet up, make sure you're in neutral with the handbrake on, door open, fire her up and run it constantly around ½ to ¾ revs and listen closely. You may not be able to tell when the fan is locked up, but you sure a hell will notice the quiet when it frees up and slows down.
Or, even better, get someone else to run it and stand at the side and stick your hand in where you can feel the airflow, obviously, without doing yourself damage.
Lastly, if the vehicle is not overheating and there's no oil seepage on the shaft, the fan is doing exactly what it's supposed to do, so the best thing you can do is nothing.
it stiffens up when it needs to due to the thermostat built into the front of it.
but oil when cold is thicker, so there is more drag which in turn makes the fan turn.
remember its basically an auto transmission torque converter. it pumps oil to make the fan go around. the thermostat operates a valve to allow more oil to push the fan faster.
i would check its operating correctly every now and then. oil loss generally goes unnoticed and the first most people know about is when engine overheats in summer, and with diesels that can crack the head.
And if you're really concerned about it overheating, get an "Engine Watchdog", pretty easy to fit and have a settable alarm.
