fluttering noise?

[1quick6]

Can anyone think of some good things to check when trying to find a fluttering noise? It is always there when cold and gets quieter as things heat up, but it always seems to be there. I can especially hear it with the windows down driving beside a car in the next lane. It just sounds like a "fuh duh duh duh duh" It isn't a mechanical sound, it is more like air. I think it is coming from the driver's side but I can't be sure. The car runs great and I recently replaced the headers and crossover pipe with a known good set thinking I was leaking exhaust somewhere with my factory originals. After the header swap, the sound is EXACTLY the same. The replacement headers have remflex gaskets as well. Maybe I should try to get a recording of it so you can hear it. The car doesn't seem to be leaking exhaust anywhere. It has an open K&N filter.

I just can't track down this noise. The car is running well and making great boost, not sluggish at spooling.

 

[QUIP'6']

you are going to have to post a clip. did you check with a hose in your ear and move it around to find the sound. sounds like an exhaust leak at the crossover. does it do this al the time or just cruising.

 

[IrvJr]

Does it happen after you let off the throttle after running into the boost? Its normal. Called turbo sneeze.

 

[TurboBuRick]

You answered your own question. I think you know where to look.

 

[1quick6]

Here is a video clip. I tried driving by parked cars to see if it would bounce the sound back to me better. It definitely isn't the horse sneeze from letting off the throttle. I know what that sounds like. It actually does horse sneeze late in the video (1:18 or so), but that's not what I am talking about. It's a constant deal. My laptop speakers are terrible, so hopefully it is more audible for you guys.

[video=youtube;_4NNfGPqXjk]http://www.youtube.com/watch?v=_4NNfGPqXjk[/video]

 

[TurboTGuy]

That sounds like some type of plastic part flopping around in the wind to me.

Air dam might be loose or something????

 

[QUIP'6']

you can try opening hood and having someone you trust that knows the car put the ebrake on, chalk tires and put in gear and try to spool up and see if you can imitate the sound. the video and explanation is unclear of when it does it. does it do it in boost or just cruising?

 

[broke]

does it have ablow off valve?

 

[1quick6]

you can try opening hood and having someone you trust that knows the car put the ebrake on, chalk tires and put in gear and try to spool up and see if you can imitate the sound. the video and explanation is unclear of when it does it. does it do it in boost or just cruising?

I will have to investigate more. It does it ALL the time, whether in boost or just cruising. I don't notice it at idle, but I do after it gets rolling just cruising along. Like I said, originally I thought it was the headers so I replaced them and the crossover and added remflex gaskets. The sound is still exactly the same. There is no blow off valve. Admittedly, I am terrible at finding noises. It changes with RPM more so than physical speed, so I don't think it is something flopping around.

Thanks for the replies so far. I will try to get a better sound sample. It does it all through the video, but you only really hear it the best when I am passing a parked car so you get the sound bouncing back.

 

[oc192]

SPeedo cable? During the winter months here, I get the same sound and it was suggested that I have the speedo cable re-lubed. During the summer months when it is over a hundred here, the noise goes away. When it drops into the 60-70s here, the noise starts to come back.

 

[QUIP'6']

As said. Above diconnect the speedo. From tranny
I also heard that sound when a headgasket leaked out toward header

 

[aminga]

I will have to investigate more. It does it ALL the time, whether in boost or just cruising. I don't notice it at idle, but I do after it gets rolling just cruising along
Thanks for the replies so far. I will try to get a better sound sample. It does it all through the video, but you only really hear it the best when I am passing a parked car so you get the sound bouncing back.

Wheel bearing.

 

[QUIP'6']

Wheel bearing.

Good thought. I would do speedo at tranny first then try the brake boost to eliminate anything that involves the chassis like brakes, driveshaft,bearings

 

[1quick6]

I'm going to try the speedo disconnect first. Out to the garage. Thanks.

 

[1quick6]

Well, it wasn't the cable. I am still leaning toward an exhaust leak, but a leaking head gasket toward the header (as mentioned) makes sense. The heads have o-ringed gaskets. It has actually been doing this for years. I replaced the headers and crossover and used remflex gaskets and the sound is exactly the same which makes me buy into the head gasket leak. It runs great and very solid, so I'd just like figure this darn sound out. I am going to see if I can somehow get a better quality sound sample.

 

[QUIP'6']

do the brake boost with the e brake on and the brake to the floor out of the garage and see if you can hear it come from the engine or not. if it doesnt do it then it could be chassis or driveshaft or wheel bearings

 

[TheGovernment]

It sounds like the predator is chasing you!!!

 

[TurboBuRick]

Try and narrow it down. Is it speed or RPM related? Does it do it more under load or in higher gears?

Do you here it if you brake torque?

 

[dynoman]

When I blew a HG I didn't notice it until I was on an off ramp next to the guard rail. I thought exhaust leak until I did a compression check and one was low .

 

[1quick6]

Thanks for the continued replies.

It is definitely throttle related more so than speed, meaning I can change the noise with the throttle easily and the sound does get louder under load. I haven't tried the e-brake test yet. I do know that if I am cruising in OD, a light increase in throttle will give me a quick paced chugga-chugga-chugga. I feel like I am trying to explain something that is really best left to the trained ear. Sorry I am not doing the best job at it. It is defintiely air, so it is either HG or exhaust.

I'd like to explore the leaking exhaust from the HG possibility next. What is the best test for this? A compression test on each cylinder? One of those kits you attach to the radiator that turns the test liquid a different color if there are exhaust gasses in the coolant? It is frustrating because the car runs great, shows no obvious signs of hg problems and it is just this noise that makes me feel like I am driving a neglected 87 Chevy Celebrity.