VIDEO- please help with belt noise/rotating noise diagnosis

[billschroeder5842]

Hey all- I'm about ready to cry "uncle" on this one... the panel is stumped.

I have several posts up about chasing my engine belt/rotating assembly noise. I've tried several things but nothing seems to work? I included a video as pictures/sound is worth a thousand words.

https://www.youtube.com/watch?v=NGghmnW1PuM

What I have done since last weekend:
- New pulley on belt tensioner
- New belt Continental 4060805
- New AC bearing
- New AC clutch

I have used the "hose to the ear" method and the alternator, AC , PS and water pump all sound good under load with the AC on. I'm not sure about the tensioner- I'm happy to take it off and rebuild but I'd like to "know" that a rebuild is what is required.

As the video demonstrates, the engine sounds pretty "normal" with the AC off, but the moment the AC comes on its "chitty chitty bang-bang".

Any opinions are helpful.

[lfalzarano]

Don?t panic. Someone smarter than me will help. I had a similar issue with the chirping. After troubleshooting for days, I started the car and no noise. It disappeared. That was my good news but no help to you. Not certain on your choice of belt.


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[billschroeder5842]

Not certain on your choice of belt.


Well, I have three to choose from. One with 15k, one with 4k and one with... less than 1 minute. All are in good condition and they all seem different length but the part numbers all check out.

[Paul Workman]

I found this video regarding squeaking and how to troubleshoot the source of the cause.

For what it is worth, my belt lasts a couple or 3 seasons before the water trick indicates the belt is squeaking (especially after sitting for extended periods of tiem, e.g., winter storage, etc.) And, the video shows a belt that might address the squeaking belt issue.

https://www.youtube.com/watch?v=AEUe6uKxTv8

[32valvesftw]

I had a very similar sound on a different car and it was the idler pulley bearing. Almost sounds like the compressor itself though if the sound goes away when the AC is off. Perhaps it is low on oil? I assume it sounds fine running with the belt removed?

[Corvette95]

I will say I had a similar issue. Known good belt tensioner. Issue was wrong size pulley on alternator. It was L98 pulley which was too small causing correct belt to be too long. I would check and measure both the diameter of the alternator pulley AND the offset of the pulley from front of alternator housing. LT5's have a spacer, or if you have a Summit pulley the spacer is built in to the pulley. Either will cause your issue.

[G8nightman]

Was is making the nose before you changed anything sound like the belt might be to long.Did you compare the two before replacing them?

[Young1]

OP. You have the correct belt. I just verified that. I need you to check two things.

A. Your alternator pulley diameter should be 2 13/16 inches.
B. Distance between belt surfaces at tensioner pulley should be 3/4 inch.

The panel is ready for your answers sir.

[Hib Halverson]

I watched and listened to that footage. The recording, both video and audio, is not very good, but I get it that you've got this rattling/clicking noise when you enable the HVAC compressor.

You've thrown a bunch of parts at it...belt, tensioner, bearing clutch.

The only thing left is either the compressor itself or you have something touching or rubbing on some other part that is rotating when the HVAC compressor is enabled.

Those would be my guesses and, if it was my noise, that's where I'd go next.

[billschroeder5842]

Thanks guys- I just got my tensioner back from Marc Haibeck today. He did a rebuild for me and turned it around quickly. I do have three different belts to try (they all have correct ID part numbers but have different lengths...WTF?) so we will see what happens.

[billschroeder5842]

A. Your alternator pulley diameter should be 2 13/16 inches.


Onward!

A quick measurement shows that my alternator pulley is about 2 5/8-ish. Looks like my alternator is the L98 version. Funny, I have had it for 2 years and the thought never occurred as there was never an issue?

I'm going to put on the tensioner and figure out the smallest (is there a mark on the belt with the length?) size and give that a look.

Hib- thanks for your thoughts. I did a closer inspection and YES, I found that the tensioner was "gently" hitting ( if there is such a thing) the water pump as there is evidence of rubbing and shavings. The rub is small so I'm not worried about the WP integrity. Clearly this is the probably cause of the "chitty chitty bang bang."

Possibly the new tensioner and a "correct" size belt will correct the problem?

Stand by.....

[billschroeder5842]

OP.
B. Distance between belt surfaces at tensioner pulley should be 3/4 inch.


Well, success.... kind of...

I put everything back together and...no more knock with the AC on. Just a soft purr of the AC spinning, so I think I'm good there. The rebuilt tensioner keeping the pull off the engine seem to do the trick.

Now... I had to use the Continental 4060805 as the NAPA 060802 just would not fit- simply too small. My problem now, is that the belt surfaces from the water pump and the tensioner are only about a 1/4 inch apart. Although they did not touch when I did a couple of light revs, my guess is that it is too close.

Any idea on the next size down? from the 406805 or is the NAPA the next size down and I just have to fight it on? I'll call the parts store and see if they can help.

[Hib Halverson]

In Continental/Contitech, the next size shorter below the 4060805 (40 series, six rib, 80.5-in) is a 4060802 (40 series, six-rib, 80.2-in).

FYI, the next one down from that is the 4060801 (40 series, six-rib, 80.1-in)

I would stick with Continental. It's Elite series of Poly-V belt design is the descendants of the late-great Goodyear Gatorback design.

I use Continental belts on all my Corvettes except the '71 which uses V-belts rather than Poly-V belts.

[Corvette95]

Use the 802 and try this ... OEMTOOLS 24388 Stretch Belt Mate Kit | These Reinforced Composite Tools Make Install, Removal, Reuse of Stretch Belts Easy | Install Stretch Belts on Cars, Trucks, Carts, Skid-Steers, etc. https://www.amazon.com/dp/B01FIJZP70/ref=cm_sw_r_cp_api_i_eHjhFbKZB5C86


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[billschroeder5842]

Success! I was able to get the 802 on the tensioner. I have about a 1 inch gap between the belts so I'm feeling pretty goo. I took it out for a quick run (about 4 miles) and the AC was quiet and no unusual noises.

So... I think my tensioner "had it" and the Haibeck rebuild did the trick.