When I'm driving nearby a wall, let's say, and I either accelerate or decelerate, I can hear a funny noise bounce off the wall. It almost sounds like air coming from a deflating balloon, or perhaps the sound you get when you stick a card in between the spokes of a bicycles wheels. It's not extremely audible, and it cannot be heard when I'm in an open space, but it does seem unusual. Could I have a hole in the exhaust somewhere?

I'll take the car to my mechanic this week, but in the meantime I'd like to hear of a few ideas of what it could be.

 

Small or large an exhaust leak sounds similar: like a fluttering noise. Once you have heard the noise you will never forget it.

 

Dammit. That's not what I was hoping to hear. =\

I guess it'll need some spot welding, then. We'll find out for sure soon enough.

 

A smoke machine will show where a leak is from the intake manifold all the way back to the exhaust tips.

 

smoke machine kicks ***. But honestly, once you find the gaskets that are leaking, they will be the ones that are probably leaking everytime, so once you hear again you'll know what to change.

 

I have a borla and test pipes and my car makes the exact same noise when im driving next to a wall

 

The hiss associated with our Borla +HFC/TP set up should not be mistaken with the air fluttering sound that is produced from a leaky gasket.

 

I've got something similar going on, but I heard it was normal. It does sound like a fluttering though. It's almost like a metal on metal vibration during hard acceleration through 1st / 2nd gear or during deceleration after a hard acceleration. (Does this most noticeably in neutral revs though)

I do notice that condensation comes out from numerous joints, but no amount of torquing or tightening the clamps seems to stop it. No air can be felt coming out of these joints though. Just a slow forming condensation that appears. (At first it leaked constantly, but then I adjusted on of the clamps and it only happened during hard driving or revs)

I really want it to go away, because I hate that sound when trying to show off my exhaust. Nice deep, bass-y tone and then *RATTLE*.

 

The metal on metal sound you're experiencing is your Borla hitting the EVAP Canister (the black box on the left). I had the same sound and I had the canister relocated slightly.

Just to update: The barely audible noise happens at 2500RPM when driving. But can also be made when in Neutral, though only when the engine is slowing down.

 

make sure the H in the borla exhaust is tight mine got loose somehow and made a audio difference. I tightened it no more nose.

 

This was it here. The passenger side clamp was a little loose, which caused the pipe to move a very small bit, and caused the noise. The problem with this H-pipe is because it has slits on the side of the pipes for easier/slide-in fitment, it is much more prone to leaks, if it comes just a teeny bit loose.

This is most likely why so many people go for the Magnaflow H-pipe, and claim it's quieter - because it doesn't have those slits. In any case, the pipes were pushed back in together and the clamp tightened down stronger and at a better location.