I'm having a hard time diagnosing this squeal coming from the front of my 2000 Bravada with the 4.3. It is soon to be my stepson's truck, and we've been working on it for when he turns 16.

At first, seems like it was the standard tensioner & pulley noise that frequents my 06 GTO, so we replaced the tensioner, idler pulley, and belt. Gates everything.

Cleaned the pulleys with a wire brush and brake clean.

It seemed to help, but the noise didn't go away.

Found a hint of play in the alternator pulley, so found a deal on a NOS AC Delco Alternator and swapped it out today. Noise got worse! And it is loud now!

It sounds like it is coming from the valley area, but I'm having a hard time pinpointing it. I've done the screwdriver to ear thing, and nothing stands out as an issue.

AC compressor on or off, doesn't make a difference.

I've ran the truck with no belt, and the noise is completely absent.

I've read a lot of posts on the forum, but still struggling a bit.

I'm thinking either:

1) Bad "new" parts. So get a new tensioner, idler pulley, and belt (Goodyear part number 106087 instead of the gates)

or

2) Water pump bearing is on its way out, and a new alternator removed some play from the system, with made the noise worse. No leaking from the weep hole though, and every time I've had a GM water pump go out, it leaks first.

Sorry about the video, but not sure the best way to describe the squeal.

Hoping someone a lot more knowledgeable can help out!

Thanks!

 

This is a distinct possibility. Gates is usually good, but no brand is perfect and stuff happens now and then. Personally, I've had good luck with Dorman stuff, but that's very much a YMMV thing and new Gates parts might be just fine too.

Also really possible that the "new" alternator is bad. Can you swap the old one to see what happens? Or before you even do that, it might be worth taking a multimeter to the new one and seeing what the output looks like.

Do you have the old parts handy? Swapping any of those only takes a few minutes and might help inform decision-making. I'm a little suspicious of that idler pulley, but that's just a knee jerk gut feel from a noisy video.

Not impossible on vehicles of this age, but I'd tend to expect some weeping and/or more typical belt squeak noise at startup that would be easier to pinpoint. Replacing the pump probably couldn't hurt, but if it's otherwise running and cooling well and not consuming coolant I wouldn't do this until I had run out of ideas.

If none of those help, it might be time to start investigating things like the crank pulley or power steering pulley.

 

If you use a spray bottle to spray some water on the ribbed side of the belt and it goes away that eliminates a bad bearing or pulley but it could be pulley misalignment. If the noise doesn't change good chance it's a bad bearing in a pulley. If the noise gets louder it could be a bad tensioner out of the box. Also look at each of the pulleys form the side to see if the belt and pulley are running true or is the belt moving back and forth which will cause a squeak.If you see movement you might try a different brand belt. I've hear Gator Back belts can help with a pulley misalignment because of their design but have never tried one. Hopefully this give you a good starting point.

 

I liked the Goodyear Gatorbacks and they were touted for 'No squeal'. But I thought they were discontinued. The one belt that was supposed to be the Gatorback successor was a Continental belt and I cannot recall its brand name. Yes, it was a top of the line belt.
Have you tried the old mechanics trick of VERY CAREFULLY putting a cut off broom handle on each belt tensioner, idler pulley, Alt. pulley, A/C pulley, and listening ? You Tube's South Main Auto's Eric O. says to add an empty plastic gal. jug to the end ot the broom stick and it will amplify the bearing noise and may save your ear from the dreaded kick back, also.

 

A quick check with Mr. Google says that the Goodyear Gator back is STILL available at Adv Auto and others. The Continental belt is available at Auto Zone and others. Be sure to ask AZ for the Continental premium QUIET BELT. I would recommend the Goodyear G/B if you can find it.

 

Well, it has been a bit cold outside to really get into the Bravada more, but I did swap the old alternator back on as recommended, and it got better, but still there. Returned the alternator.

Tried the water trick with no luck.

Got a new belt, but I ended up getting a Goodyear belt, not sure if it is a Gatorback or not. Gonna give that at try, but I'll see if I can track down a Contential belt and see if that makes a difference.