Knocking noise from exhaust?

[Randomrage]

Yeah, when the car is cold, I hear a knocking noise when I take off from a stop. Seems to originate from the rear of the car on the exhaust side, and stops when the car gets warmed up. Any idea what it is?

 

[clipsit]

Do you have aftermarket exhaust? B/c my Hayame exhaust does that too. Mine rattles on the bend towards the rear of the car on the lower arm where you would put the tie rod on. Let us know what kind of exhaust you have. Also is a knocking...I know you said that, but is it more of a rattle or what? Could be some loose bolts. Have someone sit and rev the car and see if you can hear where it's coming from. Let us know man. Your setup looks sick...Definetly like it...Good work man...welcome to boost!!!

 

[Randomrage]

Ive got a Greddy Evo2 catback.

Its kind of a rattle, quick metal on metal taps in short succession when the rpms are low at takeoff. I think it may be some loose bolts, but are there any gaskets in there that couldve burnt up?

And thanks, glad to be here!

 

[andymoraitis]

You might want to make sure that everything's tight and also get the car on a lift so you can pull on some exhaust parts and see what's making contact. Chances are one of your exhaust hangers isn't lined up properly or that one of the rubber pieces that hold them has broken or loosened.

Let us know what you find,

Andy

 

[DSMcrazy3]

Before you turn the car on to see if you find the source, go to the exhaust and wiggle it with your hand to see, that way you can do whatever necessary underneath without having to deal with a hot pipe.

 

[VelocitàPaola]

Before you turn the car on to see if you find the source, go to the exhaust and wiggle it with your hand to see, that way you can do whatever necessary underneath without having to deal with a hot pipe.

Extremely good advice. Exhaust pipes have become my nemesis since I started working in shops. I have three identical burns on my right arm from changing the oil on recently driven cars.

I had a similar problem with my muffler after I first put it on. At first, I thought it was just because of my ghetto muffler - the sound was more of a rattle than a knock. After I inspected things more thoroughly, however, it turned out to be loose bolts.

 

[zyrusp]

if youre piping is too narrow at the bend of the axle....it's going to hit no matter what...use some exhaust wrap and wrap around the bend where the piping is hitting...i guarantee there will be no more rattling...

 

[DSMcrazy3]

if youre piping is too narrow at the bend of the axle....it's going to hit no matter what...use some exhaust wrap and wrap around the bend where the piping is hitting...i guarantee there will be no more rattling...

Right now we're still waiting for the diagnosis. However if it is knocking there, wrapping it with wrap will eventually fail as well. As continuous pounding(tapping) will break through it.

 

[dr1665]

Chances are one of your exhaust hangers isn't lined up properly or that one of the rubber pieces that hold them has broken or loosened.

Ditto.

 

[Randomrage]

I still havent gotten the car up on a lift yet. The car is so low I cant get up under it to see any frickin thing. Ill post an update and some pics, hopefully this weekend.