Fan Noise/Whine

[Brayden]

Heard a few complaints about the fan whine on 720s, and mine also has a bit more whine than I like. Wondering what kind of solutions people have done to quiet it up. Best idea I've got so far is putting electric fans on it and ditching the fan clutch. (Brand new water pump and fan clutch so I know its not that)

[weldingrod]

Actually, I changed a fan/clutch/pump recently and it was also whining. Turns out the clutch hub was faulty from new and didn't work correctly, the fan started spinning as soon as the truck started. I have it installed, keeps the temp normal so I'm just going to live with it.

[datzenmike]

You should be able to spin the fan with your finger but there is stiff resistance. The fan cannot be made to spin freely by itself without a push. There is a silicone oil inside that hydraulically couples the fan from the spinning water pump shaft. As the speed increases at some point it can't pull more air through the radiator and it maxes out and won't spin any faster no matter how fast the pump turns. This is sufficient for cooling and saves energy at higher speeds where vehicle motion pushes air through the radiator. If the bearing seizes the fan will turn one to one with the pump and make a roaring sound. If the oil leaks out it will slip excessively and the engine can over heat. Fan will spin easily by hand.

 

Whine is usually the alternator or the fan belt.

[NC85ST]

Or it could be one of your idler pulleys.

[Thomas Perkins]

When you replaced your water pump,was both of your dowels in place.One of mine came out,causing the propeller to scrub on the inside.I bought some new ones from Nissan.

 

 

 

[datzenmike]

I've shortened and ground down a suitable size nail for the timing cover that has the same tiny dowels.

[Brayden]

Im pretty sure everything went on how it came off, and to respond to an earlier reply, I also replaced the alternator and all the belts while I was in there. I dont hear any scrubbing from the pump, engine seems to run real smooth. The only thing on the front end service I did not replace were the pulleys

[Thomas Perkins]

1 hour ago, datzenmike said:

I've shortened and ground down a suitable size nail for the timing cover that has the same tiny dowels.

Cool

 

[Thomas Perkins]

1 hour ago, Brayden said:

Im pretty sure everything went on how it came off, and to respond to an earlier reply, I also replaced the alternator and all the belts while I was in there. I dont hear any scrubbing from the pump, engine seems to run real smooth. The only thing on the front end service I did not replace were the pulleys

Nissan still has them.I replaced my power steering one not long ago.

[Thomas Perkins]

Your fan could be scrubbing on the lower  fan shroud.You can see the end of the fan blade scuffed up on mine.I have a tie wrap holding my lower stroud tight.There is nothing down there to hold it in place.Mostly everyone has after market radiators and the shroud don't fit the same down there.Check your fan blade ends.Their is a hole at the bottom of the shroud where you can connect 2 tie wraps and connect to frame down there.

 

[NC85ST]

If it is idler pulley noise, you can just replace the bearings and not the entire pulley.