[gth]

Background:
2000 GMC Silverado extcb 4x4 5.3l 120,000km

Problem:
I have had a major (super loud) howl/squeal coming from the belt area of my truck. It happens at idle and varies with throttle position. It used to only happen when it was cold back in November and then go away as the truck warmed up but now it is persistent every time I start it and doesn't go away. I don't know if it is "cold" dependent or if the problem has just finally come to a head as we haven't had a day over -10 for quite sometime for me to check to see if the sound goes away once it warms up.

Attempted fixes:
I started it one cold morning and let it howl. I oulled off the splash gaurd and proceded to hit all the pulley bearings I could see with kroil to see if I could find the problem bearing or pulley. No dice, it didnt stop.

Its impossible to tell where the sound is coming from with the naked ear with all the noise of a running motor. I havent taken the belt off and run the truck for a bit to see if if that stops the noise.

Side note:
The alternator went south on me about a month ago so I replaced it and the battery and belt. I figured I might as well when I was under the hood anyways. All is well with the charging system now, so I think this should eliminate the alternator and the belt from the equation.


Any ideas???

I'm going to get a mechanics stethoscope and try to pinpoint the problem. What should I be listening for and where should I be listening with the probe of the stethoscope????

Waterpump/pulletys/AC pulleys etc...???

 

[unplugged]

Take the tension off the belt and check the tensioner pulleys/rollers. At 120km they are suspect. Quality varies on aftermarket idler/tensioners...I recommend NAPA
.

 

[ChevyTech]

I agree with the previous post about checking the tensioner. I would look at the idler pulley as well, They tend to rust or fall out of alignment as they get older. Good way to tell is spray some polylube on the back of the pulley and see if goes away with the engine running if not try the other pulleys. Also check the belt alignment on all pulleys. The alternator is a suspect as well, even though recently replaced. The manufactures of those things don't always use the best parts. I have had this happen to me so many times. I hope this helps, good luck.

 

[Cableguy]

The only thing I can add is they can detonate without notice and make a helleva mess under hood. (idler/tensioner pulley, that is) If it lets go. I had a 1/2 ton years ago and I kept putting it off and it almost came thru hood (made a huge dent on inner skin under hood) when it let go.
Seems like a cheap enough part, maybe throw a new belt on too...

 

[Rumpamuro]

an easy way to check also is get a crobar usaully the ones with a plastic handle work well, and put the metal part to all the parts, alternator, water pump etc. and plastic to your ear. whichever is making the noise it will be apparent which one it is since they all make noise, but the loudes one wins!