18 Sport - Engine/exhaust buzz - 3000-3500rpm? (POSSIBLY RESOLVED?)

[Odrapnew]

UPDATE (5-MAR-2024): TLDR - I believe the heat shield by the center support bearing is/was the cause.

After dealing with this periodic buzz for almost 2 years I finally decided to really look into fixing it last weekend. I tried to clamp a few of the heat shields that wrap around the exhaust, but no change. Last weekend I was under there tapping the heat shields all over and it seemed like it was coming from the foil type shields that follow the contour of the floor so I started putting some foam in strategic places to dampen the buzzing. After about 30 minutes of messing around with that, I think I found the actual cause. There's a heat shield that protects the center support bearing for the driveshaft right above the resonator. When I tapped on that I heard a buzz. I thought, hmm, interesting, what is that hitting? Turns out that heat shield was close enough to the center support bearing when it hit a resonant frequency, it would bounce (buzz) on the metal bracket that retains the bearing. I put a couple washers at the mounts of that heat shield to space it away from the bearing. So far, with my drive in to work today the buzz was not there. This afternoon will be the real test since getting on the highway from work is where I noticed it almost 100% of the time.

 

Original Post Below:

On my 18 Sport, I notice a buzz when the engine gets to about 3000-3500rpm.

I really feel it in my feet and it sounds like something is vibrating (like a panel or heat shield).

I did turn off the fake engine noise through Forscan and that seemed to reduce it, but that may have been my imagination.

 

I plan to get under the car (maybe this weekend) to check, but looking for any thoughts.

It's certified for another 10 months, so I could bring it to a dealer, but I'd like to know if it's common (or at least known).

 

Anyone else experience this?

Edited March 5 by Odrapnew
Updated Info

[enigma-2]

One common area is when one of the underbody closure panels sheads a fastener or two and vibrates against the body. Exhaust heat shields can also cause a buzzing. 

[Odrapnew]

15 hours ago, enigma-2 said:

One common area is when one of the underbody closure panels sheads a fastener or two and vibrates against the body. Exhaust heat shields can also cause a buzzing. 

 

Thanks for the input.

I heard about the fasteners before.

Some day I'll get under the car to look around. Too much time being spent on my other car projects.

[Odrapnew]

Figured I'd update this.

I did a quick check under the vehicle around where the driver's footwell is and tapped on the plastic panels under there.

I'm pretty sure it's one of the panels vibrating against the bottom of the sheet metal because when I tapped around, I could hear a slight buzz in a few areas.

One spot that was most noticeable was in the wheel well at the bottom where it looks like a couple panels are attached together with some plastic pins (or something like that).

I plan to get behind it and add some felt or rubber foam to dampen the sound.

[Odrapnew]

OK, new update. I originally thought the buzz was from the plastic panels around the foot well/wheel well.

I decided to take a closer look/listen as I had the car up on jack to swap winter treads for summer.

 

Turns out, the most likely culprit is the heat shield that goes over the resonator (I think). It's located under the car, right about where the front center console is located.

When I was tapping around, I hit that shield and it buzzed.

Unfortunately I think the only real way to remove it to add some damping material behind it is to remove the back half of the exhaust system.

Maybe sometime this summer I'll look into that, but for now, I pushed on it to add some small bends to try to get it from buzzing. Seems to have helped a little bit.

I might try to get some header wrap material and wedge it between the shield and the belly of the chassis to dampen the buzzing.

[enigma-2]

EricTheCarGuy shows how to repair a heat shield fast and cheap. I'd use stainless steel for the corrosion resistance. 

 

[Odrapnew]

I actually had a couple hose clamps in hand with the plan to do exactly that, but unfortunately, the heat shield that is buzzing doesn't wrap around the exhaust.

The 'foil' type shield actually follows the contour of the floorpan and is right up against the floor.

This isn't an Edge, but the arrows are pointing at the example shield that I'm talking about. They are thin foil type material.