Ugh. I’ve got a noise. Still.

Long shot but I don’t even know where to look. Just did timing belt; water pump, fan bracket, tensioners, idlers. It went good and no leaks. Part of the reason I replaced all the bonus parts was I was getting a noise about every 5-10 times I started the truck. I’d shut it off and start again and it would be gone. Figured it was a bearing somewhere but no clue which one. Jumped in the truck this morning and damn noise was there! Same thing, I can shut it off and restart and it’s gone. I’m thinking (maybe hoping?) it’s the actual fan?
I grabbed a video and you can hear it but don’t think I can upload. When the noise isn’t there it’s so smooth I can’t believe there’s anything wrong with it. Any ideas on where and how to start looking?

 

Go to www.imgur.com

Upload the video from your phone to that site and tell it to embed audio when asked

When it drops you into the webpage with the upload, copy the URL to that page from the address bar and paste it here, the forum will auto-embed the video.

 

Thanks - here’s the link.

https://imgur.com/a/KIuMZ3h

 

Is the fan contacting anwhere you can see? Like, with the engine off, can you see that anything has been making contact anywhere? It sounds almost like something is dragging across something in there.

 

Just went back out and double checked high and low. Nothing out of place and nothing close to the fan.

for what it’s worth I’ve only ever heard it on startup. It’s never just started making noise while driving around.

 

Sounds like a vacuum line got left off.

 

would that make it only make noise sporadically? If I hear it, shut it off and start it again it’s gone.

 

Can you pinpoint the origin of the noise with an automotive stethoscope ?

 

I agree that it could be something with the fan. If the fan blades have clearance, what about the balance of the fan or the fan clutch itself?

 

Haven’t had a chance but will try that if can.

 

This balance seems fine and it turns smoothly by hand. I don’t know much about that clutch mechanism but maybe that’s it?

 

The fan should not spin freely with the engine off. There should be resistance, but move smoothly.

 

Yes - there is resistance but it turns easy and smooth. It won’t keep spinning if I spin it around by hand.

 

Yes, if it was the SAIP vacuum line that is supposed to hook up under the passenger side of the intake. It’s got mesh braided loom it passes thru. The sound would only last for 50-75 seconds after a cold startup every time.

 

I think I would take the serp belt off, start it and see if it still makes noise. Rule out anything mechanical inside. Then I would start checking for play in all of the pulleys if the first test produced nothing. Process of elimination.

 

This vacuum hose - it tees off up there off the solenoids for SAIP, and this hose with the braided sleeve goes up under the intake and plugs in above the 2nd cylinder, roughly.I'll try to find a pic of insertion.

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Interesting- I’ll check that out. Doesn’t happen every cold start but worth a check.

 

I may have to go down that road. Just gonna be tough to tell because it seems totally random when it does it.

 

Here's where it plugs in up under the passenger side of the intake. Props to @bfunke for this source photo. When I looked at my truck a few days ago, I could clearly see it with the 4.7L plastic cover off, looking around the passenger side of the throttle body. If a hose is loose, and it's only kicking on at cold starts, this would be my #1 suspect. And the fact it goes away if you cut off the engine and start it also speaks to the secondary air injection/SAI system. It could also be that your SAI pump is going bad. Any codes logged yet?

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Take a photo of the engine zoomed out a little more.

 

Just pulled the 4.7 cover and it’s definitely there. I tugged on it gently and it’s connected down there somewhere.

 

Thats tough one.
It almost sounds like a bearing is chirping.
Have you tried the old stick trick?
Take a piece of broom handle or piece of dowel and touch it to various places where think it's coming from and put your ear up to it with a cupped hand over it.
Surprisingly enough this actually works.
Of course with a moving part that can be problematic.
But it can narrow down where it's coming from.

 

Funny you should mention that. My mechanically inclined buddy came over with a huge screwdriver earlier to do just that. Too bad after 20 tries it wouldn’t make the noise!

 

That figures....

 

This. But first test that the noise increases in frequency when you rev it a little.

 

This would be my next step.

 

Well, I figured after sitting all night my chances would be high when I cold started it this morning. Popped the hood, set up the camera and turned the key. No weird noise. That’s my concern with trying the no serpentine route. I never know when it’s going to do it.

 

Regardless, if you pop the drive belt off you can then spin the various components by hand, listening for the tell tell signs of a bad bearing. The idler and tensioning pulleys are likely candidates, followed by the tensioner itself. Then the fan bracket pulley, followed by the alternator and AC (you do have the AC off when you've been checking...right?). There's a lot of moving parts...one of them is bad.

 

Upgrade your audio system....eliminates all the unwanted noise everytime!