My car, like many others had the 75-80mph "dash" buzzing that I eventually figured out was the outside cowl under the wiper arms buzzing. As many others have clarified, this is relatively easy to identify by the buzzing being reduced by using recirc on the ventilation settings.

Many people say they have found the windshield side rubber flap to be torn from the plastic cowl. Mine did not show that, but the maddening buzzing was still there.

I don't much like to screw with stuff, so I just ordered the updated cowl PN and went to install it today.

On my car, turns out the middle metal snap clip was missing from the front edge of the cowl. Based upon the condition of the parts, the middle clip was never there, and it was just loose enough for the front lip to buzz against the mounting surface. The weatherstripping provides some resistance to this but under enough force it would buzz. Tapping on the center of the cowl without the weatherstripping there made it obvious as the source.

My car was a very early 2008 and I suspect it was just built without the center clip. There is clearly a cut out in the trim where that 5th center clip is supposed to go. I just used a couple speaker mounting clips I had on hand and secured them with some adhesive. Drove the car and the buzzing is gone.

I could have checked for this in 2 minutes by simply removing the front weatherstripping and it would have been obvious. It would have taken a $0.50 metal clip and less than 5 minutes to replace, vs. a $80 part and 20-30 minutes to replace removing wiper arms and a couple other trim parts in the process.

Bottom line if you have this buzzing and the rubber trim is not torn, pull your weatherstripping off and check to see that all 5 metal retaining clips are there. Don't do what I did and waste money and time.

Chances are if 1 car was built like this, quite a few of them were.

 

I'm having the same issue with no obvious tears. Thanks for the heads up. I'll be checking into it soon.

 

Having the same problem, and thought I would check for that middle clip as per your post.....guess what? No clip! Apparently never installed at the factory.
Thanks for the tip

 

My new 60th Anniversary has a recall for that. They ordered the part. I don't know what years it covers.

 

Pictures would be nice if you got any. Mine just started it

Thanks
Lisa

 

My 08 Z as the buzz. It's killing me. I will check this out.

 

Thanks for the info. My 2008 is doing this also.

 

Some people have reported using some double-sided tape under the loose cowl.

Might be worth a try.

 

Doubel-sided 3M tape is the new duct tape.....

Fixed the noise on my wifes GS. My Vette never had it....same year too, '12.

Go figure

 

Image below shows the snap clip locations. There are clearly 5. One could also make a strong argument for running a small bead of silicon between the two flat surfaces the clips clamp together. The weatherstripping pulls right off, it is not bolted or glued, only held on by the shape of the weatherstripping.

I did a decent amount of internet research before going out to buy the part. I wonder how many people that have done this even notice how many places there are for snap clips. I betcha more than a few have been replaced with that missing clip being the actual root cause, and they just happen to buzz less due to being a new (stiffer) part. Double sided tape or RTV would do the same thing, stiffen the part up just enough to stop the buzz.

The problem here is that I can see the same part has two different failures that cause a similar noise. If the rubber strip fails, then the cowl will be free to float due to a loss of pressure and will buzz. If these front snap clips are missing, then the assembly won't be as stiff and will buzz. The AC recirc setting matters because it influences airflow in that area. Having the fresh air port open must create more turbulence that excites the cowl.

The good news is that the problem is very easy to diagnose as this part with the recirc/on-off test at speed, and you can check for the missing clips in seconds with no tools, same as you can check for the rubber flap being torn. This is just one very simple thing to check before messing with sealants/RTV/tape or buying a new part, and something else to make note of if you are replacing one with a torn flap.

Those that have this problem know it must be fixed. That goddamn rattling was driving me nuts, it's not a small GM-like rattle or squeak. I can now drive ~75-85 again to keep up with Michigan highway traffic.

 

My 07 has been buzzing for the past year.

 

Good info. Thanks for posting.

My '08 had the same problem. I simply applied black electrical tape accross the whole thing. It's barely noticable. It's been on my car for 2 years now with no problems.

I'm going to pull off the tape & check for a missing clip.

 

My '12 GS only started making this highway-speeds wind noise/buzz after I hit a fairly sharp road bump while getting onto the freeway, so obviously something came loose, also since it hadn't made a sound (even @ 160+) for the past 8K miles. The rubber edge of cowling where it meets the windshield is in perfect condition too.

I didn't want to hassle with a dealership warranty visit, so I checked it out myself. You just open the passenger door, gently pop the windshield cowling's 2 rubber locator nubs out of their holes in the top of the quarter panel (easily seen/accessed) & then pull the windshield cowling back a few inches.

The fix is easy (for the '12-'13's at least), pull back/out the passenger side of the windshield cowling a few inches, & insert tape into the 2 cowling clips to take up any play between the 2 clips & the windshield. I'm pretty sure this is the cause; the clips don't grip the bottom edge of the windshield tightly enough, so high wind turbulence causes the cowling to move & buzz on the windshield.

I cut two 1"x1" pieces 3M dual-side adhesive foam tape & inserted them into the clips, then reattached the cowling by pushing the cowling & clips back onto the windshield. The whole process took about 10 minutes.

I noticed my 5th (middle) clip as referenced above wasn't there either, but there was no play/seperation at that point, so I don't think it was the cause of the buzzing, but we'll see.

 

I noticed the buzz start on occasion on the drive home from museum delivery. Gotten a little worse a year later so had dealer take a look. The part is on order. Mine is a '12 coupe.

 

I used clear silicone adhesive under the trailing edge lip, was about $5 at the parts store, fixed.

 

did the same with black silicone....

 

had my oil changed at the dealer, went for a cup of coffee,when I got back i seen the wipers on the bench and the old cowl cover on the floor,they said there is a recall on the cowl cover because of high speed vibration that is on my 2013 427

 

I need to get mine to the dealer as it has done it since day one! If GM knew about this problem since 08 why wasn't it addressed??? I had it to the dealer twice last fall about this buzz and they didn't fix it, any idea what the recall number is and what years it covers?

 

im on my 3rd cowel. factory. warranty replacement. and the one i just did myself. whats this recall bologna about?

 

Mine stated making the noise the night I picked up the car from my blower install