Ear piercing screeching on cold start

[DropTopDon]

View attachment 368037

It was 40 degrees this morning which is the coldest it’s been in a while where i live and on start up my engine started making this noise. It is LOUD. Any ideas what it could be? I am thinking serpentine belt maybe though it looks brand new

 

[GPK03X]

Alternator or idler pulley or belt tensioner. Remove belt and spin the pulleys by hand should tell the story

 

[Chris]

Alternator or idler pulley or belt tensioner. Remove belt and spin the pulleys by hand should tell the story

X2

 

[LONGJP2]

To figure out which one, spray them one at a time with water till it goes away.

 

[DropTopDon]

Will check it out tomorrow morning. Could I also turn the engine on while the belt is removed just to confirm it is belt/pulley related? Also how can I check the belt tensioner since that is stationary? Though I noticed my belt tensioner shakes a little bit. Is it supposed to be completely still? It shook on my old TJ too

 

[kincaid.0678]

You can completely unthread the bolt from the tensioner. It just threads into another piece that’s attached to the bolt that’s used to tighten and loosen that same pulley. They shouldn’t really have too much play in them. If you can spin the pulley and it stays spinning it’s probably good. If it stops or grinds when spinning them by hand the bearing is shot inside them.

 

[cpwolf]

That sounds like a bearing bad in a pulley, not the belt spinning. At least over my iPhone speaker.

I had this and changed everything, to realize the Harmonic Balancer was separating and the belt was screeching because of it.

I would start like someone suggested. Spray bottle of water, spray the belt, and if sound goes away (water creates a grippy that helps) then you’ve got a belt or harmonic causing belt type issue.

Y
Sound stays, you’ve got a bad pulley bearing if soem sort, would be my order of Ops.

 

[Jerry Bransford]

You can completely unthread the bolt from the tensioner. It just threads into another piece that’s attached to the bolt that’s used to tighten and loosen that same pulley. They shouldn’t really have too much play in them. If you can spin the pulley and it stays spinning it’s probably good. If it stops or grinds when spinning them by hand the bearing is shot inside them.

That's only how it was done on early TJs like your 97. Later models like his 04 use a spring-loaded idler pulley.

 

[Inline.TJ]

Bad pulley. I'd wager it's that idler pully. If you have an extendo-magnet thing press the magnet against the bolt holding the pulley and you'll be able to feel the vibration. Not like the motor running vibration feeling but more of a buzzing.

 

[DropTopDon]

Took the belt off and spun all the bearings by hand, sure enough the tensioner pulley made noise while spinning. Thanks for all the sound advice. I’ll replace it and report back. OEM replacement only or can I just pick one up from the auto store?

 

[Inline.TJ]

Anything with a Timken bearing will be fine.

 

[kincaid.0678]

That's only how it was done on early TJs like your 97. Later models like his 04 use a spring-loaded idler pulley.

Oh gotcha. My 97 is a completely different monster I’m finding out lol

 

[Jerry Bransford]

Oh gotcha. My 97 is a completely different monster I’m finding out lol

I loved my previous 97 TJ (stolen) and yes there were definitely some differences.

 

[kincaid.0678]

I loved my previous 97 TJ (stolen) and yes there were definitely some differences.

I love mine too even though it’s a rusty broke down pile of shit lol if I can get it running again I’ll love it even more.

 

[CODE5]

@DropTopDon did you get this sound resolved? What did it end up being if so?

 

[DropTopDon]

@DropTopDon did you get this sound resolved? What did it end up being if so?

I did not. I bought a new belt tensioner/pulley and replaced it. That was not the issue though. Whenever the weather is below 40 on start up the jeep still makes the noise. Idler pulley seems fine too

 

[Andy-WhiteTJ]

I did not. I bought a new belt tensioner/pulley and replaced it. That was not the issue though. Whenever the weather is below 40 on start up the jeep still makes the noise. Idler pulley seems fine too

Check for small vacuum leaks.

 

[elkivory]

I did not. I bought a new belt tensioner/pulley and replaced it. That was not the issue though. Whenever the weather is below 40 on start up the jeep still makes the noise. Idler pulley seems fine too

Did you ever get this noise resolved? Mine started squealing when it is cold and stops squealing after less than a minute. Also, what belt and tensioner did you buy? Thanks

 

[DropTopDon]

Did you ever get this noise resolved? Mine started squealing when it is cold and stops squealing after less than a minute.

I did not. No vacuum leaks that I found either. It still does it whenever the weather drops below around 35 degrees. I noticed that it changes pitch in noise when I put the transmission in drive.

Start with your pulleys and bearings though. That’s usually the issue for most

 

[TimV]

I'm not qualified to speak on this beyond a suggestion. Hopefully more knowledgeable sorts will chime in:

OPDA?