Seeking advice for “Harmonic Sound Under Acceleration”

Hello fellow Taco owners!

I’ll try and make this posting clear as possible.

Just today. I’ve notice my taco, under acceleration (or load), makes a harmonic sound. Sort of whistle like, but not really… I’m trying to find the best wording possible. At idle, there is nothing. The sound comes at 2k RPM’s, yet it doesn’t get any louder or higher pitch at higher RPM’s.

I inspected the pulleys and belt. All of which look fine. Nothing is loose when I gave them all a tug. I tugged on the fan and its housing. Those are fine too, but I noticed this. After tugging on the fans housing, my glove brushed against the cooling fins (maybe its the fans housing?) and created a harmonic sound. I lightly brushed my finger tips against them and was able to create a similar sound. Maybe its the fan pushing the air around (during load) that was creating my symptoms I’m describing to you all? Or am I fooling myself?

I called the stealer-ship and advisor told me initial inspection will be $225, if all things are found to be in warranty condition (Example, after market parts will void). Nothing is out of pocket from me. I’m still under powertrain warranty for another calendar year or 10k miles (whichever comes first) since I’m bone stock.

It’s been a hot day, nearly 100 degrees F. Don’t know if that’ll contribute to this condition.

Any advice is well appreciated.

Cheers!

 

How long have you had the truck?

Is this noise new?

What has changed?

 

Had truck since OCT 2018

This noise is new. Today afternoon new. Didn’t hear it in the morning.

Very hot day today once Sun was up. Other than that, nothing else.

 

Are you sure it is coming from the front because the rear diffs are notorious for howling/failing on these trucks.

Another one is air whistling past rubber trim on the windows/doors. Mine makes a kazoo sound occasionally.

 

It's coming from the engine bay 100%. I did my inspection in my drive way, at idle speed, hood open, and wife on gas pedal to 2k RPM's recreating sound.

 

If it has one (I don’t remember) did the radiator fan clutch engage?

 

I don't know where to check for that.

Can you point me the direction?

 

They do, https://www.google.com/search?q=201...5gBAKABAcgBAsABAQ&sclient=mobile-gws-wiz-serp

 

I'll take a look at it in the morning

 

I know you said it's a harmonic (sort of a whistle) noise, but given the ambient temperatures you mentioned,
could it be this?

https://static.nhtsa.gov/odi/tsbs/2022/MC-10207964-9999.pdf

 

Nothing out of the vents.

While inspecting the noise. I was hovering engine bay and wife on gas pedal loading engine to 2k RPM. Harmonic sound, 100%, came from belts/fan area.

 

I just checked the fan and confirmed I have resistant while attempting to free spin the fan. All is well.

 

All of those fans/pulleys have bearings, maybe one of them is on the way out?

 

Update:

I ran the taco this morning. It’s 64 degree F outside. Loaded engine to 2k RPM, which produced nothing. Tried again few more times producing nothing.

In my professional-amateur mechanical trouble shooting. I’m chalking this up to “over thinking” in something is wrong and trying to attack a simple problem before it becomes major.

I’ll update if issue returns. Thank you all!

Cheers!

 

When its super hot and the clutch engages to spin the fan faster, there will be a different noise.

 

Did not know that. Thank you for new information.

Cheers!

 

When I replaced the fan clutch on my '94 6.5TD Suburban, when it got hot enough to engage, it sounded like a helicopter!