Intermittent Whistle for over 1 Year Please Help

[cajun_cummins]

I have been dealing with an intermittent whistling noise for over a year. I have finally managed to capture a video of it so others can hear the sound as well.

Initially it was very seldom heard, but it has gotten worse recently.




The truck is an 07.5 with EGR, DPF and CCV Deletes as well as 5" turbo back exhaust. All other components are stock, except for the air intake which is an S&B and been on since 2016. I run a Smarty S67ME on level 1.

The noise is not turbo whine and is not affected by boost pressure. The noise most commonly occurs between 1500 - 2000 RPM usually while accelerating. I have never heard it above 65MPH. During the cooler months it would be quiet for days at a time. I recently discovered that my EGR delete coolant hose was leaking. This lead to most of the coolant draining out and the truck nearly overheating. While the truck was leaking the sound got more frequent. I fixed the coolant leak and bled the air out of the system and the sound has gotten less frequent.

It is a very high pitched sound and initially I thought it was a bad ground on something, but then I discovered that it was coming from the engine bay and not the cab.




The noise has occurred in Neutral, Park and All Drive Gears so I don't believe it is in the transmission. The coolant lines remain firm while the engine is running so the water pump seems to be working well. The alternator has been replaced since the noise started with no effect on the noise. The fan clutch is aftermarket and was replaced about 3 years ago ( the noise started around 1 year ago ). There has never been a loss of boost or vacuum that I could find so it does not appear to be a leak in these systems.




It has also made the noise with A/C off and on and with the unit in heat. Also it has made the noise regardless of what setting the AC fan is on.




As far as I can tell there has been no affect on performance since the noise started, it is just obnoxious.




I am leaning towards a problem in the fan clutch since the fan usually gets louder when the noise stops. Just would like some other opinions.

I have linked the video below so you can hear the sound. Thanks for reading.

 

[JR]

It is hard to tell by video but it sounded like a bearing or belt squeal at the point where the noise stopped when the video wasn't picking up the wind noise. If you think it is the fan, take it off and run it again to try to duplicate the noise. If it is still there remove the belt and spin each component by hand to check for any worn out bearings. You can briefly run the engine with the belt off to try and duplicate the noise again, preferably with a cold engine, first start of the day.

 

[cajun_cummins]

Thanks for the reply.

So to add some more information. I went yesterday and spent several hours in the driveway trying to make the sound and establish a pattern.




It only makes the noise if the fan clutch is fully engaged and the engine is revved. I can hear the difference in the fan when the fan clutch is engaged, it roars like a jet engine. Once the fan clutch engages if I rev it up to around 2K - 2500RPM it will make the noise more often than not. Other than that it will not make the noise at all.




This leads me to believe something in the fan clutch or fan clutch bearing. Any idea how to check the bearing?