NP300 coolant thermostat housing changing

[Jameskixg]

the fan always spins. there is enough drag with the oil to make them spin, tho not at full speed as the air resistance counteracts it.
as the hot air off the radiator heats the thermo valve which then allows more oil to be pumped around which puts more power into the fan so it can pull more air through.
the only time they spin freely is when they are stuffed. quite common in older toyotas.

remember they are not a clutch, they are a very crude torque converter. they don't engage, they are hydraulically coupled, it simply allows more fluid to flow to drive the other half.
however the silicone oil is really thick especially when cold. hence why they tend to roar a bit when first started.
if nissan has thick oil in it (because they are worried about overheating) then its going to get more fan speed than normal.

the only other thing i can think of is if the fan is on back to front.

Going back to what you said about the thermovalve being open allowing more power to be put through it, could this keep the fan running due to the valve being stuck open?

 

[tweak'e]

the other thing could be if the fan is louder when the ute is up to temp. that might indicate that the air coming off the radiator is hot. if the cooling system is not working properly or lack of air flow through radiator, the water temp goes up and so does air temp exiting the radiator.
temp sensor behind the radiator to confirm. or pull up engine temps with ecu reader. dash gauges suck and never show proper temps.

Going back to what you said about the thermovalve being open allowing more power to be put through it, could this keep the fan running due to the valve being stuck open?

yes, but thats pretty rare to have two of them stuck. if you pull the old one open you should be able to tell. heat up the thermostat and see the rod move. it shouldn't take much heat.

 

[Jameskixg]

the other thing could be if the fan is louder when the ute is up to temp. that might indicate that the air coming off the radiator is hot. if the cooling system is not working properly or lack of air flow through radiator, the water temp goes up and so does air temp exiting the radiator.
temp sensor behind the radiator to confirm. or pull up engine temps with ecu reader. dash gauges suck and never show proper temps.


yes, but thats pretty rare to have two of them stuck. if you pull the old one open you should be able to tell. heat up the thermostat and see the rod move. it shouldn't take much heat.

The fan actually sounds w

the other thing could be if the fan is louder when the ute is up to temp. that might indicate that the air coming off the radiator is hot. if the cooling system is not working properly or lack of air flow through radiator, the water temp goes up and so does air temp exiting the radiator.
temp sensor behind the radiator to confirm. or pull up engine temps with ecu reader. dash gauges suck and never show proper temps.


yes, but thats pretty rare to have two of them stuck. if you pull the old one open you should be able to tell. heat up the thermostat and see the rod move. it shouldn't take much heat.

dont have the old one unfortunately fan is the same volume throughout the drives, if anything possibly the smallest bit quieter once warm. I’m going to plug the computer into the car tomorrow & hopefully I’ll be able to see something on there. This really has me stumped honestly. I’ve seen people post on Facebook with the same issue & all they’ve done is replaced the clutch but I’ve done that & nothing doing my head in this is hahah

 

[Old.Tony]

I tested mine with a hair dryer. You can watch the valve turn as the bimetal strip (looks like a coil) gets warmer.

 

[mbramston]

Did you solve your noisy fan ,James?
I had a similar problem with my 2015 NP 300 diesel ,from new. Was very noisy on startup but would then turn off after 5 mins. Was a very loud roar initially .At first service Nissan said it was normal but later heard that some Nissan dealers were replacing them under warranty with a much quieter fan . Too many complaints. Mine is still noisy after startup 150K later ,but still a great car. Fan does come into play again when weather is very hot. But your fan must have been annoying, when on all the time. Martin