Exhaust Rattle HUNT!
 

Let me start off by saying that this rattle is driving me insane.

2008 RX8
35k miles
RaceRoots single exit exhaust
Oem Cat
Oem header


How to reproduce:

while IN MOTION: rattle at 1800-2300rpm
What it SOUNDS LIKE: from the driver seat while driving, it sounds like "shhhhh" as if you were to say shhh quiet in a movie theatre.

While MOTIONLESS: rattle only happens if i rev to 3-3.5k and let it drop. Rattle occurs from 2800-1800
What it SOUNDS LIKE: from behind the car, metal marbles in a can
IT IS NOT THE CAT, ive tried taking the catback portion off and it does not make the noise!

When under the car it almost sounds as if there is something in the canister of the catback.
THIS IS NOT THE CASE, my previous RR exhaust was sold and i received a replacement from Brice brand new. My old RR single made the same noise and i could not isolate the rattle, initially i thought that it was the packing inside the canister.

My old RR single was on the car for only 2k miles and the rattle became audible after taking a 2hr drive to watch the grandam race in south jersey.

My new RR single has been on the car for less than 50 miles(4 days including today). I THINK that the rattle wasnt there when i first put it on, but im not sure.

My old RR single exit exhaust was sold to JeffH on the forums, i called him up yesterday and asked if he had any rattle, he said he heard NO RATTLE. This leaves me to assume that it is something other than the exhaust.

THINGS I HAVE TRIED:

I tried pushing up against the catback - didnt work
I tried taking the tip off - didnt work
I tried pushing against the heatshield - didnt work
I tried switching out exhaust gaskets - didnt work
I tried tightening all of the catback nuts and bolts - didnt work

PLEASE HELP ME!!!!!!

<3


EDIT-REASON TO BELIEVE IT MAY BE THE CAT AFTER ALL...


The sound seems as though it is coming from the cat area, and then i hear it again at the canister of the catback. My brother seems to believe that it gets louder as the heat goes up, but i cant hear any difference.

I found this thread dealing with the heatshield
https://www.rx8club.com/rx-8-discuss...rosion-234180/

maybe this is the culprit? Last i checked it looked fine.. But why would i hear it in the canister of the exhaust? wouldnt i just hear it at the cat area??

Heres something you can try to remove any linkage to the body as part of the equation.

1. Throw the car on stands

2. Place the jack under the rear canister

3. remove all exhaust hangers from the cat to the rear (should be 2-3 since it is single exit)

4. make sure that the exhaust is secure, it may slide a bit when you turn on the car, maybe have someone keep a hand with a rag on it until the car is started.

5. check for noise

what this does is 2 things, 1 removes any touching of the catback to the car. 2 the jack is going to dampen the vibrations in the canister. see if there is a difference.

Note: remember that the catback is still bolted to the cat. You only want to remove / disconnect the hangers, do not lower the exhaust,

im going to try that right now, ill be back in 15-20.

car is on ramps, but i dont think that should make any difference.

1.3 litters of furry had a rattle with this exhaust. maybe he will chime in.

My rattle comes from the cat back hitting the frame by the differential. Mine sits to far to the passenger side. Looking under my car it appears my oem mid pipe is bent. Where the cat back meets with the mid pipe that flange is almost touching the driver side of the tranny tunnel.

I really only have a rattle in certain idle conditions, usually with the a/c on. Once in a blue moon I'll hear it in the 2.5k-4k range. Since I upped my idle with the AP (875)it happens a lot less often.

I figure I will either have to replace the midpipe or have a shop bend it. I tried using header wrap on the pipe in that area to stop the rattle, but didn't last very long.

^ i remember when you first posted about that. Sorry it didnt work with the wrap.

I unhooked both hangers from the canister portion of the catback and it still made the rattle, just slightly less.

for poops and giggles i tried to put my ear as close to the cat as i could get from the side.. guess what, i heard the same noise from the cat. so i guess my cat is on its way out.

Im going to look up the warranty information i have, i think the cat is a 5yr correct?

I know i have to go back and re read the newbies thread about waranty info, what are some common copouts mazda dealerships like to say when they dont want to replace the cat from warranty??

I know my milage is pretty high for not changing the coils plugs and wires yet, but i havnt misfired so even if they looked up the codes, i havnt had a cel come up yet.

Do you guys think its my cat? initially i thought the "marbles in a can bad cat" noise would happen all through the rpm band.

do you guys thinks its my cat? Im not getting any powerloss or a CEL..

i thought you said you took off the cat and it still made noise.

nope,

my old rr single had a rattle, sold it and the new owner reports no rattle

my new rr single is making the same rattle

i took the catback "canister" portion off of the catback (my exhaust looked like... header->cat->catback pipe 1) I dont THINK it made a rattle, but my brother said yesterday that it probably did, but the car was so loud i couldnt hear it... makes sense :dunno:

I dont know what else to do

get a garden hose. stand away from the car with one end of the hose to your ear, get someone else to run the hose along the exhaust, holler when you hear the rattle. That should at least help you pinpoint.

great idea! ill keep this thread updated.

does the length of the hose matter? i think the shortest i have is a 50ft.

the shorter the better, most guys would use a garage stethoscope but as you can see, i have found alternatives since i don't have one lol. Test the length by having one person talk into the other end and see if you can hear them well.

This stuff sounds stupid but hey when you lack some tools these methods work lol.