Supercharger noise

[Bassasasin]

My 2000 Ultra has a supercharger (M90) loud whine similar to a bad or loaded alternator bearing whine or air in a power steering pump at idle and in boost. It's not coupler clatter sounding. Listening through a long screwdriver to my ear the loudest source is at the pulley serpentine way out on the snout. All other quarters of the supercharger are greatly quieter. Not having much experience I've never heard bearings whine, only scrape and grind.

My question is, "Could the sound be transmitting out to there from internal supercharger problems?"

Joes' Garage wants $1700 replacing the entire unit. I have replaced intake manifolds and similar levels of maintenance and am hoping it's just a faulty bearing on the end of the snout.

Thanks

[Tech II]

If noise is coming from the snout of the SC, the whole unit does not have to be replaced, just the end.....forgot which company sells them....did you check the synthetic fluid level for the SC?

[Bassasasin]

I hope it doesn't hurt anything but I removed the serpentine belt today and disabled the boost, removed and sealed the vacuum to the boost valve assy. After a 10 mile checkout drive the MPG still is high, perhaps better? No codes thrown, no more noise. Luckily the serpentine is only used on the SC.

[Bassasasin]

The level was almost full. The oil was clean too! I added about an ounce of the stinky stuff. I think it takes 7oz. . I turned the pulley with the serpentine off everything feels very smooth but noisy only when its back together loaded and running with the belt on. Idler wheel and tension wheel is smooth too!
Thanks for the clue on the snout. I ordered one. $200..

[Jrs3800]

Yep sounds like the snout bearings are going... No promise that they are but very possible...

when you reassemble Please use the correct Lubricant for the charger... I prefer the GM SC Oil over most others...

Let us know how you make out..

[HotZ28]

Hopefully, the snout you ordered will come with the pulley installed, if not, you will need a pulley puller to remove the existing unit and more than likely it will warp/bend upon removal. Good luck, and if you find that you need a complete M90 unit that has been totally rebuilt & sanitized with a 3.4" pulley, PM me for more info. I have a spare ready to go, sitting on the shelf.

FYI:

8/25/2011

Click on a thumbnail to see the full-size image

GM Belt Tensioner May Cause Supercharger Failure

This information applies to all GM vehicles equipped with superchargers.

Problem: Premature failure of supercharger bearings.

Cause: When the belt tensioner starts to fail, belt tension increases dramatically. This tension shows up as side-loading in the supercharger rear bearing.

Solution: Periodic inspection of the belt tensioner should be part of the regular maintenance routine. Before operating the replacement supercharger, the tensioner must be inspected and replaced if defective. Unless the tensioner is checked and replaced as needed, supercharger-bearing failure will occur, causing premature catastrophic failure.

While this problem is prevalent on GM vehicles, this inspection should be performed on all belt-driven supercharged vehicles. Please check the service manual for the recommended inspection and service.

Note: This bulletin is supplied as technical information only and is not an authorization for repair.

Source: CARDONE Industries, Inc.