First of all, let me apologize for yet another "help me figure out what this noise is" thread. I know these threads are a dime a dozen, but I searched and couldn't find one that seemed to match what I'm hearing. I also understand that without actually hearing the noise yourself it's difficult to make an accurate diagnosis, but I would appreciate any help. Ok, end of disclaimers.

On my 2002 MCS JCW I hear an extremely high pitched sound during acceleration coming from the engine compartment. I hear it the instant I tap the gas pedal. It happens in any gear, and even when I tap the gas pedal while the car is sitting still idling. I can be cruising along at any speed and decide to suddenly give it more gas, and I hear the noise. NOTE: This is a separate noise from the supercharger "whine." I'm familiar with the "whine" and this is not that. It sounds almost like a bird chirp or maybe a dog whistle. At times it sounds like metal against metal.

I tried to make an audio recording of it to attach to this post, but I think the frequency range of this noise is so high it didn't make it into the recording.

My car has the JCW tuning kit and an Alta CAI. Everything else is stock.

Should I check for a bird's nest under the hood or what?

Thanks in advance.

 

Maybe the belt it's about to go or maybe the crank pulley?? Maybe I'm sure that you already checked that area I hope that you can find the culprit

 

Could be the belt tensioner, the belt itself, the crank pulley or the idler pulley making that noise. All are in the same area so can be hard to pin point. Best thing is to get an auto stethoscope and carefully poke around to isolate the noise. Either way I'd be cautious driving the car.

 

Probably the whistle of air passing the plate in the throttle body. The more open the intake is the more you will hear it. I noticed mine when I added the ALTA intake.

 

Yeah, I'm hoping it's just the normal Alta CAI noise, but I bought the car with the Alta already installed so I've never heard the engine without it. And I don't have a stock intake that I could swap in to see if the noise goes away.

 

my guess would be something on the serpentine belt, wether its the belt it self, tensioner or the crank pulley.

i have the alta CAI as well, i do get a wistle from now and then, but its slightly more throttle than cruising where i will get a wistle, not under loaded accel (i may have that, but the pulley and exhuast would drown it out)

 

You should check the intake tube where it meets the bypass vale and when it meets the air box. I made my own cai with two three inch aluminum pipes, a silicone reducer, a silicone coupler to join the two tubes, and a k&n filter. Testing at idle in the garage sounded fine, road test I heard a noise similar to what I think your talking about I hadn't tightened the clamps between the pipes so it was drawing air through gap and causing noise. Tightened it up and it was perfect

 

My 2005 MCS recently developed the same high pitch ringing / whistling sound in the area of the tensioner, pully, etc.

The original tensioner was replaced under warranty at 40,000 Km. I now have 156,000 KM and the belt was replaced at 136,000 KM.

I have no idea which component is beginning to fail it's probably a good time to invest in a stethoscope.