Exhaust Knock?

cmconti · #1 (**permalink**) 04-23-2009, 12:24 AM

I have a 2008 2.5S and I hear a knock noise that sounds like it's coming from the center underside of the car. It does it even when the car is off, I'm thinking the exhaust. I don't want to take it to the dealer until I can pin point the problem, I know they won't hear it and just give me the run around.

Wondering if anyone else is having the same issue?

theshocker3.5 · #2 (**permalink**) 04-23-2009, 12:26 AM

is it a knocking sound? like, ping, ping ping, ping?

it's fine if it is

cmconti · #3 (**permalink**) 04-23-2009, 12:31 AM

No, just one single loud knock thats totally random. Sounds like someone threw a rock against the car.

fourGfrost · #4 (**permalink**) 04-23-2009, 01:00 AM

my 07' does this too. I contribute it to the expansion and contraction of metal; probably exhaust. But im not sure. It's normal

xeene · #5 (**permalink**) 04-23-2009, 01:26 AM

my car does it too, also sounds like metal contracting and expanding. sometimes happens when i come to a stop at a light or after i park my car in garage and shut the engine off.

velanzia · #6 (**permalink**) 04-23-2009, 01:37 AM

i always get a similar sound as soon as i get the car out of the garage in the morning, drive or about 1 minute ... bhooom, or brooom something like that .. some metal pop noise.

so much memories with this car .. lol

xeene · #7 (**permalink**) 04-23-2009, 01:44 AM

i think it's the heat shield, but it doesn't bother me.

fourGfrost · #8 (**permalink**) 04-23-2009, 02:33 PM

Yah the heat sheild would be my guess. And now that you mention it, I remember being in the drive-thru a couple of times and hearing the popping/knock sound. like someone threw a stone at a peice of sheet metal, it is very randomn. no worries

Vondrak · #9 (**permalink**) 05-01-2009, 08:41 PM

If you look at your exhaust pipe roughly 1/3 of the way back from the front. There is a piece of flat metal that is welded on. It looks like it is connecting two sections of pipe together. Look at the weld and see if it is broke. Take a flat head screwdriver and push down on it. This is where the heat shield is breaking. I had mine replaced 4 times.

matt1111 · #10 (**permalink**) 07-18-2009, 04:22 AM

Ya, mine just recently started doing that pop sound , every time i turn off my car or when i stop for a bit, it sounds like the heat sheild pops, but everytime i take it to the dealer guess wut it doesnt do it. Will i e able to recognize it very easly if the heat sheild was cracked..????? its a 2008 altima 2.5s coupe..this sound really bugs me..

jemcleod · #11 (**permalink**) 07-18-2009, 05:19 AM

I have this issue too. It is normal.

matt1111 · #12 (**permalink**) 07-19-2009, 01:22 AM

Really, that kinda sucks if its normal, so im guessing there is no way of gettig rid of that noise then..i just looked under the car and can't find anything wrong with the heat sheild..

but if its normal how come some other coupes don't do it..i do have 20000 on it..may thats why pluse it just started doing it recently like several months ago..or may i just didnt notice it at the begining..but

SOOO THERE IS NO WAY THIS WILL HARM MY CAR????????

kev1n536 · #13 (**permalink**) 07-19-2009, 07:14 AM

is the knocking sound something that sounds like tiny rocks or sand hitting the under carriage?

matt1111 · #14 (**permalink**) 07-19-2009, 09:02 PM

it sounds like someone threw a big rock and hit the car from under neath, at first i thought it was coming from the engin, but its actually coming from under the car right where the heat sheild is..i jacked up the car and i hit the heat sheild and it sounds exactly the same like some cheap metal..

Its a big clunk or knock or pop, maybe like a big pop like the metal against metal..its hard to explain but thats wut it sounds like, every time i turn of my car..it does it once sometimes three or four times in row..i thnk im going to record the poping sound and post it.

im hoping its just the cheap metal , and wont hurt my car