One way to find from where the noise is coming is to remove the serpentine belt and see if any noise remains. If the noise is gone, it's likely it's a rotating assembly such as the idler pulley or tensioner, alternator, power steering pump, etc.
If that doesn't help, you could try a mechanic's stethoscope to listen to various areas around the engine to see if it could be a bearing or lifter, etc.

 

You didn't think about new belt, tensioner, idler pully when you had the belt off and water pump out? There's two belts BTW. One on the ac with it's own tensioner wheel which gets ignored often and not changed. Plus it's at the bottom of everything and tends to get a lot of road grim on it.

Narrow it down like GB said before you throw parts at it. Usually when I pick up a used vehicle one of the first things I do is replace the belts and tensioners/idler pullys.

Thank you both. I guess I was so focused on replacing the water pump and thermostat that I didn't really consider doing the tensioner and idler - lesson learned. I was not aware that the A/C had it's own tensioner - that's good to know. It's supposed to rain tonight and all tomorrow - but once the weather clears, I'll follow up on your suggestions.

 

I've had the truck for a few months now - second owner. I had a 2004 Colorado before (with that weird i5 engine, a great little truck until it was totaled by a drunk driver.)

Over the last few weeks, I've started noticing some squealing noises while at idle or low, around town, speeds. I replaced the water pump and thermostat yesterday. My thought was that this was probably the source of the noise, and it's probably time to replace the water pump anyway. On the plus side of the ledger, I successfully replaced the water pump and thermostat (combo thermostat housing / thermostat) with no leaks. On the negative side of the ledger, I still have the squealing noise.

So my question - how can I diagnose what is causing the noise?
It is good practice to replace the idler and tensioner anyway as part of "I'm replacing the water pump anyway"?

Thanks for your assistance.

You didn't think about new belt, tensioner, idler pully when you had the belt off and water pump out? There's two belts BTW. One on the ac with it's own tensioner wheel which gets ignored often and not changed. Plus it's at the bottom of everything and tends to get a lot of road grim on it.

Narrow it down like GB said before you throw parts at it. Usually when I pick up a used vehicle one of the first things I do is replace the belts and tensioners/idler pullys.

 

You can use a long socket extension. Becareful of the belt. When the truck is running put the extension behind your ear and place the other end where you think the noise is coming from. You should be able to find where the noise is coming from. Just don't get too close too moving parts.

Sent from my moto g power (2021) using Tapatalk

 

Ok, now I'm not sure if I'm relived or worried
I didn't drive the truck for about a week for various reasons. And now, the noise seems to have disappeared. Should I be concerned? It does seem that I ought to go ahead and replace the tensioner and idler pulleys, just for good measure. Thoughts?

 

refresh everything you can on the serpantine. cheap and no brainer. also takes like 10 minutes to do.

get all ac delco parts and take care of this

 

Yes sounds like a belt or pulley . Remember measure twice cut once . Don’t throw parts at it like the dealer 😂🔧

 

Might help find videos on YouTube or other social media . Ones that are geared toward your model truck with same noise .see what they come up with and how they found the problem 😎👍