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I have a 1998 Pontiac Grand Prix GTP, with the supercharged 3800.

I recently made a trip from Meridian, MS to Cincinnati, OH, and back again (roughly 600 miles one way). With the car being relatively old now, and having over 220k miles on it, I was a bit concerned about her making the trip. She did great the drive up and back, until I turn onto my road and am literally less than 1/10th of a mile from my drive way.

I slowed down to turn onto my street, while coming out of the turn and accelerating, there was a loud "clunk" type of sound from the front passenger side. The car "bogged" down (by which I mean the RPM's dropped, lights dimmed, power steering was affected etc) and almost went dead, but immediately caught back up and kept running. Needless to say when that happened I stopped, to make sure nothing weird was going to happen. I noticed a slight "roaring" noise coming from the car now that wasn't there before. So I "limped" her the 1/10th of mile to my car port and popped the hood to check her out.

My immediate thought was a bearing from a pulley had gone out. I visually inspected the belt and pulleys with the engine both off and running. There was no wobble or "dog-tracking" on any of the pulleys and the "roaring" sounded like it was coming from higher up. The closest I could pin it down to was from somewhere around or in the super charger.

I know little to nothing about super chargers other than the general theory behind how they work, but certainly nothing along the lines of their internal workings etc.

TL;DR: "Roaring" noise apparently coming from the super charger.

My question (after that really long story): Are there components inside of the super charger that could fail and cause a "roaring" sound? If so, what potential damage would this cause to keep driving the vehicle (not referring to damaging the super charger further as it was not maintained properly by the previous owner and was on its way out anyways)?

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I found a very nice visual breakdown of the supercharger here: Can you tell if the noise you're hearing is in the "snout" of the blower? Does the noise change in pitch based on engine speed? Or is it constant? Did you have an oil leak from the blower? – Bob Cross Aug 8 '13 at 19:38
@BobCross Thanks for the breakdown. I have been unable to pin point exactly where it is coming from on the supercharger. facepalm I forgot to mention that the noise goes away at higher RPMs (usually over ~1500). There were no visible oil leaks that I could see (I haven't looked at it in a couple weeks, I'm ashamed to say, because it has been running fine other than the noise.). I will take a closer look this evening when I get home from work to double check on the leaks. – bullrider Aug 8 '13 at 19:45

ok this is the image of a Roots blower supercharger used in a Pontiac as suggested by Bob Cross so as you can see there are two lobed rotors so maybe the central rod on which they are mounted (i don't know what they are called) would have been worn out and got loose so the rotor would have moved a little bit from the axis and would be rubbing with the other rotor that would be producing the roaring sound

enter image description here

and at a higher rpm the flow of air and the speed of rotation would be causing the rotors not to meet for a long time to make that sound. I think this is a problem as i am not a pro so just take it as advice

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FYI: This is the wrong type of supercharger for the OP. This is centrifugal, not a Roots blower as on the Pontiac. – Bob Cross Aug 9 '13 at 14:25
i said you i am not a pro i just googled for supercharger – Dimensionless Aug 9 '13 at 14:26
Indeed. But the suggestion of a worn bearing is still a good one. BTW, a centrifugal supercharger looks very much like a turbo (if anyone was interested). – Juann Strauss Sep 9 '13 at 9:59

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