NP300 coolant thermostat housing changing

[Jameskixg]

Hey everyone my viscous fan isn’t disengaging… I’ve replaced the viscous fan & still isn’t disengaging so now im thinking it’s the coolant thermostat being stuck open… so my question is where Abouts is the thermostat & how do I go about changing it, all hell is appreciated. Thank you

 

[tweak'e]

how can you tell its not disengaging? what problem is it causing?

 

[Jameskixg]

how can you tell its not disengaging? what problem is it causing?

It’s constantly spinning, even on start up the fan is blowing, it’s never not blowing. It’s so bloody loud too especially when getting up to 3k rpm

 

[Old.Tony]

It will always spin, the test to see whether it's actually pushing hard is to watch the fan as someone else turns off the engine. If the fan stops with the engine, it's fully engaged (which it should be when the engine is at normal operating temperature). If the fan runs on a little after the engine stops, the hub hasn't fully engaged the fan.

I don't know if the NP300 uses an oil-based viscous hub. Anybody?

 

[Jameskixg]

It will always spin, the test to see whether it's actually pushing hard is to watch the fan as someone else turns off the engine. If the fan stops with the engine, it's fully engaged (which it should be when the engine is at normal operating temperature). If the fan runs on a little after the engine stops, the hub hasn't fully engaged the fan.

I don't know if the NP300 uses an oil-based viscous hub. Anybody?

Okay so if I get the missus to turn the car off when it’s cold & it stops with the engine is that an issue as it shouldn’t be engaged when the engines cold?

 

[Old.Tony]

Okay so if I get the missus to turn the car off when it’s cold & it stops with the engine is that an issue as it shouldn’t be engaged when the engines cold?

Correct. If it's oil-filled, maybe someone put too much in it or it's damaged.

 

[Jameskixg]

Correct. If it's oil-filled, maybe someone put too much in it or it's damaged.

I don’t think they are oil filled, I’ve just gotten a brand new one put in too & still constantly staying engaged. I’m thinking it may be the spring on the temperature sensor is stuck open causing the fan to think the cars hot all the time

 

[Old.Tony]

I don’t think they are oil filled, I’ve just gotten a brand new one put in too & still constantly staying engaged. I’m thinking it may be the spring on the temperature sensor is stuck open causing the fan to think the cars hot all the time

Surely the temperature gauge in the dash would give you some indication of this - does it always sit at "normal" temperature?

 

[tweak'e]

first thing is most manufactures use oil (silicone) filled mechanical fans. otherwise they are electric or hydraulically pumped (ecu controlled). no one uses a fixed fan because it would tear itself to bits at full rpm and they loose power.
the thermostat simply opens and close a port for the oil to go through. possible its jammed, but i've never heard it actually happening. easy to check on the old one tho.

there was an issue with early ones that roar until warmed up. you could get it replaced by nissan. possible they got the wrong fluid in them.
a think a few people on here had them changed.

testing, test when hot. fan should continue to spin a little bit after engine is off. they will usually stop straight away when cold due to the thickness of the oil.

 

[Jameskixg]

Surely the temperature gauge in the dash would give you some indication of this - does it always sit at "normal" temperature?

Yeah always at normal temperature, never once gone over, I should’ve mentioned this before but I forgot, the fan is always spinning at the same rpm as the engine, like it’s constantly locked in with the engine, the higher the rpm the louder the fan gets

 

[tweak'e]

otherwise take a video of it and post it up. noise is very subjective.

 

[Jameskixg]

first thing is most manufactures use oil (silicone) filled mechanical fans. otherwise they are electric or hydraulically pumped (ecu controlled). no one uses a fixed fan because it would tear itself to bits at full rpm and they loose power.
the thermostat simply opens and close a port for the oil to go through. possible its jammed, but i've never heard it actually happening. easy to check on the old one tho.

there was an issue with early ones that roar until warmed up. you could get it replaced by nissan. possible they got the wrong fluid in them.
a think a few people on here had them changed.

testing, test when hot. fan should continue to spin a little bit after engine is off. they will usually stop straight away when cold due to the thickness of the oil.

I should’ve mentioned it’s like the fan is locked in with the engine, if the engines at 3k rpm the fan is too & is crazy loud

 

[Jameskixg]

otherwise take a video of it and post it up. noise is very subjective.

Sounds like that, the higher the engine rpm the faster the fan spins & the louder it is, it’s always spinning at the same rpm as the engine no matter what

 

[tweak'e]

that doesn't sound all that bad. things sound a lot different in person.

can you turn the fan by hand (engine off of course)? if cold it will be stiff.

 

[Jameskixg]

Yeah can still spin it by hand. I just don’t understand why it’s so loud? I’ve never heard another Nav sound like this

 

[Jameskixg]

that doesn't sound all that bad. things sound a lot different in person.

can you turn the fan by hand (engine off of course)? if cold it will be stiff.

i don’t understand why it’s always running at the same rpm the engine is, I’m scared to go past 3k rpm because it sounds like it’s gonna explode to pieces

 

[tweak'e]

with it spinning by hand its not doing the same rpm as the engine, it just looks like it.
it might be doing higher rpm if they have to wrong oil in it.
they are basically a simple torque converter inside it.

what you could try is pull the old one apart, looks like they screw together, and replace the oil. not sure if nissan sells it, i know toyota does. then you can compare how thick the oil is. if the new stuff is thinner then i would try that and see what its like.

 

[Jameskixg]

Right I’ll give that a crack, I’ve also heard that when the fan is running if you try stop it with say a piece of cardboard it should stop/ slow down right? I’ve tried that with this one & it just chewed right through it, I’m onto my second viscous fan & just struggling to understand why its doing this, I’ve never heard another Nav like this

 

[Jameskixg]

Are

with it spinning by hand its not doing the same rpm as the engine, it just looks like it.
it might be doing higher rpm if they have to wrong oil in it.
they are basically a simple torque converter inside it.

what you could try is pull the old one apart, looks like they screw together, and replace the oil. not sure if nissan sells it, i know toyota does. then you can compare how thick the oil is. if the new stuff is thinner then i would try that and see what its like.

they not only supposed to engage when the cars getting hot too?

 

[tweak'e]

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.