Weird buzzing noise upon cold start...

[NVHunter83]

My truck has a erratic, buzzing sound coming from the front, passenger side area of the engine bay. It is louder when the truck is first started and is cold. The last few days its been 3-6 degrees below zero out and the truck has the "buzzing" noise which is pretty loud.

It disappears when the truck is up to operating temps and it is not there during the summer when it's warm.

The noise is coming from the area of the belts between the engine and the fan. I have a video of the noise so I'll try and figure out how to upload it.

Thanks

[NVHunter83]

Here's a link to my video

Engine buzzing - YouTube

Engine buzzing - YouTube

[NVHunter83]

Ok, so I looked into the engine bay today and saw what I think is the accessory pulley just below the alternator bouncing around as the truck was running.

Are any of the pullies suppose to move at all?

[6.0f250firstcar]

No, they aren't supposed to move.


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[04hdfatboy]

Are you talking about the idler pulley?

[NVHunter83]

Yes, I think so. I watched it this morning literally bounce as the belt moved over it.... I don't think it's supposed to do that.

After work I'll take another video of the pulley and post it. Sounds like the "buzzing" noise is coming from the same area.

[04hdfatboy]

No the idler pulley is not supposed to bounce. That is likely your problem.

[6.0f250firstcar]

I'd be willing to bet that's your problem


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[NVHunter83]

Ok thanks guys!!!

[NVHunter83]

Ok here' what's bouncing while the truck is running. The diagram I found said its the accessory pulley. #8.

Also here's a video of the pulley bouncing, it's hard to see but you can see it slightly bounce with the light on it.

You Tube

You Tube