FIXED: "Flutter" sound only under boost. Ideas? - 2006 Grand Prix GT

Video 2
http://www.youtube.com/watch?v=3nWEJ2WQLTw

Video 3 (the forums will only allow 1 video per post)
http://www.youtube.com/watch?v=WGGbfgKm4Ww

thats a good one for sure.

id take the sc belt of and go for a ride see if the sound is still there. could be a bad pulley or the the sc is making the sounds.

does it feel like its loosing power as you get in the gas?

No noticeable loss of power. It also isn't the "rocks tumbling in the supercharger" sound (as that is all of the time since the supercharger is always spinning). I would think that even at high RPMs that I would get the sound since the supercharger is powered by the belt and the belt is moving whenever the engine is running, but it is only under boost. I guess I could have taken the belt off though and just "disengaged" the supercharger to see what would happen. We will see what the shop comes back with and that might be the next step.

If I could equate the sound to anything, it would be a "tinny" (not tiny) year airy sound. Almost like an exhaust leak, but it is under the hood vs. under the car(manifold leak maybe?) and that could be a possibility to some degree if the leak was only present under increased pressure caused by the supercharger.

Again, just rattling off ideas. Not saying that is what it is of that it is even mechanically possible.

bad coupler is heard at idle only, but bad bearings and the rotors tagging each other can make that noise for sure. or even a bad belt pulley.

does resemble a exhaust leak sound a bit too. but i think you would hear that in park revving the engine up.

Yeah, it if did it while in park or neutral, than I could isolate it under the hood. Wouldn't THAT have been nice. :p

The sound seems to come from the driver's side when driving, and when I sat in the passenger seat, it too sounded like it was coming from the driver's side. With the belts and pulleys on the passenger side, those sound sources don't seem to match where the sound is actually coming from.

With the supercharger snout (and thus bearings) on the passenger side as well, plus the fact that a bad bearing should be audible even with the engine idling, I am betting that isn't it.

Keep the ideas flowing though.

The shop called me back. Granted they are not experts (by their own admission) on superchargers, but they had some ideas.

On a side note, even with the car on the lift and in drive, the supercharger doesn't kick in, so they were somewhat guessing as well. They did say that it does not seem to be doing damage to the engine as it didn't sound like any sort of "normal" noise they they encounter ever.

So they said that it is about a $500 "gamble" that what they think it might be actually fixes the problem.

Their thoughts were: Wastegate Valve and Control Solenoid, plus a couple of new air hoses.

I swear that I replaced the solenoid already once, but it kicked a code at the time (an easy fix with a price of about $35 from Rock Auto). The "wastegate valve" sounds like a "turbo" part, and not a supercharger part and I can't seem to find reference to it anywhere. Not sure if they meant the bypass valve??

I would need to source the hose, but all in all, about $110 in the 2 main parts, and then some hose and a pretty easy fix, IF that fixes it. Since the solenoid is the only thing that connects back to the computer, it is the only thing that would kick a code of some sort. If it is working (since my boost isn't limited and I am not getting a code), then the valve and maybe hoses seem like the next logical thing to try. Again, not saying that it will actually fix anything.

EDIT: I DID replace the solenoid already, but that was 4 years ago per this post: http://www.grandprixforums.net/threa...-valve-trouble

EDIT: Unless it needs a replacement "Actuator kit" (GM 89018120) which is closer to $200 for that part...

take the belt off and drive it already.

that shop dont have a clue lol

I'm at work. Need to pick up the car after work, pop the belt, and see. Of course if the Supercharger is disengaged by the belt, then it still could be the valve or vac line, but I guess it would eliminate any "non-supercharger" component.

I will pick up one of those "free rental" belt removal tools from Advance Auto to make it easier to remove.

15 mm socket wrench to the tensioner pulley. if you got 1/2 drive use that cause its easier with a longer ratchet, or use a 3/8 th breaker bar or a little pipe in the 3/8 ratchet.

Sounds good. Last time I had to take the belt off, it was to replace the water pump and coolant elbows, so I just borrowed the tool. Since the supercharger belt is on the outside of the main serpentine, I was hoping that it would be easier to get to, but wasn't sure. I will give that I shot instead of making the small trek to the parts store to borrow a tool.

no tool needed, never used one. i use the two little pipes from my bottle jack on the end of my ratchet. works like a charm. its not that its hard to move, but it sucks to hold it there with no leverage.

Yeah, it was very easy with the 15mm socket and breaker bar.
So.... I started off before that by disconnecting the small hose that goes from the supercharger to the valve (what they called the wastegate). Problem persisted.

Then I removed the belt for the supercharger and guess what??? I could still hear the sound, just not as loud as with the supercharger connected. I had to have the window down to really hear it, and it was only when really getting on the gas, which matched what I was getting before as I needed to stomp on it, somewhat, to get the supercharger to kick in.

So the supercharger doesn't seem the be the problem child that I thought it was, but it make the problem a lot louder.

The shop manager told me that he thought that it was an exhaust leak issue, and admittedly, my downpipe is probably due for replacement. I had to get it welded about a year ago (I knew it was a short term fix) right where the flex section is. They told me that some spots were like trying to weld rust together. The shop looked for obvious leaks around the engine, and didn't find any exhaust or vacuum leaks.

They also put it up on the lift, and without any resistance from the tires on a road, the supercharger wouldn't kick in then either to really isolate it. Not sure what else to look for or how to try to isolate it more.

FYI, he called it a "flutter" sound too. Even without me saying it first.

ok, put all the hoses back on and the belt, and seafoam the engine. the exhaust will smoke and show a leak hopefully.

you'll want to have it on ramps so you can look under it when you start it back up, then have someone rev the gas while you watch for smoke to leak out. a rag in the tail pipes may help force the leak to show too.

Interesting idea. I Seafoamed it about a year ago and didn't get a ton of smoke, but might be worth a shot. Of course I had to change the plugs right after per recommendation of the instructions.

you dont have to change the plugs. let it soak for like 30 minutes, then fire it up. the longer you wait the more carbon it breaks up. and the more it should smoke.

I will see if I can do that tomorrow. Yeah, if I had cheap copper plugs, I wouldn't worry so much, but with $8 a pop plugs, I don't want to change them. Then again, there shouldn't be a lot of build up anyway to foul anything since I did it a year ago is all.

Last time I used a line right above the supercharger instead of the brake booster for naturally aspirated engines.

i use the booster line. mine smoked like a muther f er lol but some are cleaner than others of course.

I wonder if that is why I didn't get much smoke. People were stating that the booster line on a supercharged engine would strip the protective coating off of the supercharger "rotors" or whatever they are actually called, so I didn't do that.