Satchmo

Hey guys!

The other day as I was parking my new me to GTO in the garage I heard a slight metalic rattling noise when I turned the car off. I immediately turned it back on and did some engine revs to see if I could reproduce the sound. 2 days of driving later here is what I have found. If anyone has any info it would be greatly appreciated:

1. Sound happens between idle and 2000 rpm when engine is decelerating (although sometimes i can hear it when accelerating out of 1st between 1-2k rpm)
2. Happens whether the clutch is pushed in or out, in neutral or not, moving or stopped. Forward or reverse. So i'm pretty sure that rules out the clutch/drive train/etc.
3. Sound seems to be a little worse after the car has warmed up, but it is present even when first turned on.

Here is the kicker...

I crawled under the car... (carefully - blocks behind tires, e-brake on very well, car in gear..yadayada)

I could not see ANYTHING that looked like it was rattling. I was actually pretty impressed with how clean it was under there.

4. Sound seems to be coming from the middle of the car.

More info: car has stainless works stainless steel headers along with their hi flow cats. The rest of the exhaust (cat-back) is the stock GTO exhaust with the SAP mufflers. Everything underneath the car (the exhaust hangers?) are all these very thick red rubber band looking things and i see no metal to metal contact. All the headshields aren't touching either. It's not a pinging sound due to bad gas or anything (always use 93 from various name brand gas providers). It literally sounds like there is a penny somewhere around the cats (either just before or just after).


So what i'm wondering is... what the heck do i do at this point as a DIY'er besides taking it to a shop? I actually thought about disconnecting the exhaust at after the cats and starting it up and seeing if the noise is still present. If it went away I would be super happy and I could have a super loud car for the woodward dream cruise ;-)

Any help on how to properly diagnose this would be greatly appreciated. I know a video/sound clip would probably help so I will work on getting one of those in a couple of days.

Also for something like this do folks just bring their rides to Midas or something or should I look into a specialty shop or dealer? I dont want to pay out the *** if it's just something stupid.

Last bit of info - I actually have plans to upgrade the cat-back at some point to something a bit louder at idle/low RPM. Was thinking of going the spintech route. Maybe this is a good reason to upgrade as if i took it to a shop they could put the new muffler on after fixing the sound problem.

P.S. this just started randomly, i didnt hit any potholes or anything. Aside from this small annoying noise the car runs like a dream!

Aceldama

It could be that some of the media inside the cats has come loose and is rattling around inside.

d50h

iTrader: (1)

check header bolts

RedHotG8

iTrader: (1)

It could be a heat shield rattling.

rperk

X2 X3 and X4

ShoddyHog

iTrader: (1)

I had the same noise, and that's what mine was. The collector to mid bolts were not torqued properly by the moron I had install them.

Like someone else said, it could be a broken internal part of the cat, but doesn't that usually happen with stock cats, and not the high flow ones from SW or Kooks? Maybe they still have it happen too...I try to stay away from exhaust section of forums.

Satchmo

Done! They were all tight on both sides of the engine (where the headers connect to the block) (God I love the room inside the GTO hood/LS2... I could actually get a rachet in there with a little finesse

The rest of the bolts i will test tonight. Need to go get a lift and a torque wrench after work tonight.

My plan is to take the passenger side cat completly off (two clamps with 14mm bolts). If I hear rattling when i shake it or if i start the car and the rattling stops, then i know the cat is the culprit.

At that point if i can 'shake' the broken 'media' ? guessing metal bits of the honeycomb filters in the cat out... i may just try doing that and putting it back in. If that's a no go i will just order a new cat from stainless works although i would be a little concerned that this went out with so few miles. I bought the car with 14k on it and i'm pretty sure the headers weren't put on at zero miles. So MAX this thing could have on it is 17k.

Any issues running without a passenger cat for a few days or would i be better off just leaving it in and dealing with the low rpm rattling (which can be accomplished by turning my radio up )

Satchmo

More info: I did try lightly tapping different parts of the exhaust (and the cat that i think is the culprit) with a rubber mallet and couldn't get anything to make a noise. So it's definitely whatever harmonic is being put out between 1000-1500 rpm that causes the noise.

Also i noticed the metal rattling noise occurs more when i am going up an incline. like when i go up the parking structure at work or pull into my inclined driveway at home. When i'm declining (going down the parking structure, the noise does't happen).

So that is further evidence it's something rattling or possibly a small piece of busted off metal/media in the cat.

I should know for sure shortly and I will do a nice write up of everything so that if anyone else has this problem they know what to check. I did a bunch of googling and searching on this forum and LS1GTO and tons of posts point in different directions... ie.

1. check the exhaust clamps (done mine were all hanging with thick rubber bands, nothing rubbing or loose or missing)

2. check heat shielding (done - nothing is rubbing, all bolts holding heat shielding up are tight)

3. check muffler/exhaust clamps from headers all the way to tailpipe (doing this tonight)

4. check cats

Some forums suggested that it might be a throwout bearing in the manual transmission, but the way to rule that out is if the noise happens whether the clutch is in or not and if the noise happens whether you are in neutral or in gear.

Also since the noise happens whether i'm moving or stationary that rules out a noisy rear end ;-)

I appreciate the help for a noob like me. It felt cool getting out in my garage and 'working' on my car (putting tools to metal). I know many of you would probably have this figured out and fixed in 30min. Just know those of us who are newer really do appreciate the advice and input

Stay tuned!

Death{AW}

iTrader: (6)

your headers might be hitting bolts on the sides of frame.

Death{AW}

iTrader: (6)

there are 4 bolts on each side they hold small brackets.

Satchmo

Update:

Dammit! Almost thought I had this figured out! So I got some 12,000lb rhino ramps from pep boys and they worked awesome. No problem getting the GTO with SAP bumpers up or down. Had my brother guide me up and down no issue. Note this also worked for his GT500 later on in the night.

Anyways...

I was under the car for a good 1.5 hours. Check every bolt, nut, heatshield, clamp, etc.

I noticed BOTH of my rear O2 sensors seemed 'loose' they were not tight at all like the front O2 sensors so i thought 'AWESOME I FIGURED IT OUT!" So i hand tightened them with an adjustable wrench, started the car and !!!!!!!.... Nope! Still rattling... DAMMIT!

My brother took a video of the sound and I will try to upload it later and link to this post.

My plan for tomorrow afterwork is to get it back up on the stands and loosen the 2 clamps on the passenger side cat. there is another piece of metal between that and the h-pipe so i need to loosen that clamp and undo 2 bolts on the h-pipe.

I am HOPING that I will be able to pull the stuff apart and get the cat out. Is this the usual way for removing a cat? The cat is in there so tight it's almost like the pieces are welded together (they aren't).

Just wondering if i will have to remove the entire exhaust just to get the cat off or if i can just disconnect everything from bottom end of the headers to the h-pipe and 'muscle it off'.

if i can get that all off, i'll fire it up and PRAY the noise stops. If it does i know it was one of those pieces... if it doesn't... i might be giving up at that point and taking it somewhere.

Is there any issue with me taking it for a spin with the cat removed and the pipe from the cat to the h-pipe connector removed? Do i need to worry about the car bouncing around and bending the headers up or anything? or should i try and get a piece of straight pipe or another cat before i really drive it?

As always help is appreciated (

402GOAT

iTrader: (2)

I once had a 2000 ss Camaro that had an exhaust rattle. Turn out to be the o2 sensors themselves. They had a metal sleeve like peice on them on the end that the wires stick out of the was rattling. Maybe wrap yours up real tight with black tape and atleast eliminate them as being a possible problem

Robofuzz

Here's my exhaust rattle adventure:
http://www.gastiresoil.com/showthread.php?t=2626

96WS6guy

iTrader: (1)

I literally just had this problem. I have headers and mids and a stock cat back. Same description of when it would happen. Turned out to be my drivers side muffler was ever so lightly rattling against the heat shield!

Satchmo

i really really WISH my problem was that simple...

So i just spent 3 hours under the car again with my brother. Undid all the clamps, undid the rear 02 sensor and pulled out. Started trying to rotate the pipes to get the cat out...



....really.... it WILL NOT come out.

Whoever designed the stock resinator on the 05/06 GTO should be tortured and shot.

There is 2 pieces of pipe after my cat that connect into the resinator. I got the bolts off this pipe and resinator but i can barely get a rachet up into the bolt on the read end of the resinator and upon more careful inspection the bolt is WELDED to the resinator... are you kidding me?! Is this how it comes stock for real? Why in the WORLD would they do this unless it was to keep everything from rattling and avoid warrenty issues.

So essentially to get my cat out.. i need to take off BOTH SIDES of the entire exhaust from the cat back to the muffler...

OR

undo the bolts to the header bolts on the engine block which I as a complete novice AM NOT comfortable with at all. I have no idea how to properly torque them back into place and whether or not i may damage the exhaust gasket and all that crap.

I'm not sure if i could just keep pulling on that pipe between the cat and resinator and eventually get it off or if i should just spend another 40 min... put all the damn clams back in place and take it to a shop and just pay them to do this...

what a pain in the ***! I think i'm more frustrated with the fact that I CANNOT do this by myself without extreme amounts of effort for something that should not be this hard.

I could go through all this to find out the cat is fine... although when i tap it i hear a little rattling, but then again i tap the other 'good' cat on the drivers side and hear a little rattling as well...

all this and woodward dream cruise in 1 day away...awesome! Love how this randomly popped up on Monday after the car has been flawless for months.

Satchmo

so after I whined on here awhile I got back to it... discovered i only had to undo 2 clamps and unbolt the mufflers and was able to just pull out the entire resinator and exhaust pipes.

To do this i had to back up my car onto the ramps... definitely will be investing in some floor jacks... something about being under a almost 4000lb car with only 1 or 2inches of space between my face and hot metal for hours at a time was a bit unnerving and peaceful at the same time.

Update:

So I have removed literally my ENTIRE catback exhaust, mufflers, resinator, everything!

Damn I started the GTO and I swear it was a mix of Devil, hard rock, lion, and fire breathing dragon.

It was about 9:30pm so I literally idled down my drive way and down the block as best I could (in 1st gear... literally like .05% throttle). My brother hopped in and we went for a quick cruise. HAHAHA this thing sounds like a race car. First car I ever took everything off and it sounded amazing. WAAAAYYYYY too loud for a daily driver or even a cruiser, but for this weekend I will sound like a race car!

Woodward dream cruise here we come!

Note: So even though the exhaust is literally about 350% louder and I can literally feel the rumbling of the exhaust directly under my ***... i can STILL hear the little rattling noise at idle and right between 1200-1500rpm.

Long story short by the time I got all the exhaust off by backing up the rhino ramps I didnt feel like pulling forward with my car sounding like a stock car, carefully turning around in the street, repositioning the ramps, getting up the ramps one more time, and waiting another 30min or so for the cat to cool down enough to be able to start wiggling pipe. So i just hand tightened the exhaust and went for a spin.

I'll enjoy my car this weekend and try not to get a loud exhaust ticket. I'm technically running headers into the cats and then the tiny 6 inch pipe after the cats with the 2nd O2 sensor in it is my 'mufflers' All the muscle cars will be out tomorrow and not like i'm going to be out annoying people at 2am. I'll go out and have some fun and have my baby parked away around 8pm or so.

After it cools off i'll spend some time this weekend or next week to actually pull the cat and see what's up.

All in all this has been a royal pain in the ***, BUT, i have actually loved working on my car. It is very rewarding and probably wouldn't be such a pain in the *** if i had more clearance under the car.

Driving up on those rhino ramps is seriously a test of fate. They work well with a spotter but i put 50lb weights behind them because they keep slipping on the garage floor without them.

Stay tuned!

Satchmo

Update:

So enjoyed woodward dream cruise with no exhaust... woohoo...

so finally got around to removing the cats and sure enough BINGO!!!!

BOTH of my stainless works high flow cats were busted. The inside mesh/medium was sliding around in there. Apparently they only tack weld these things in place and if they get too hot the welds can break thus making the insides slide back and forth and 'rattle' at certain rpms.

This really sucks and I was told it can be from unburnt fuel getting into the exhaust and causing it to get too hot and thus break the welds OR

I was told that this could be caused from the car sitting too long without running.

I'm really hoping this 2nd reason is what happened with mine since the car pretty much sat for 3 years with very little driving (none in 2010, maybe 100 miles in 2009 and 200 in 2008).

So i called stainless works who put me in touch with their cat vendor and they ended up giving me a decent deal on 2 new high flow cats. They also tossed in some straight pipes for $20 just in case i want to try those out as well.

So i will let you guys know how it all turns out... i'm kind of worried i have some kind of tune issue that may blow out the new set but no way of knowing without taking it in again once i get the cats installed to some shop in the area to do some data logging.

i am relived to know the sound was exactly what i thought it was all along. kinda stinks the fix was a few hundred bucks though ;-/

anyone running no cats? any issues? other than having to get the back o2's tuned out?

ShoddyHog

iTrader: (1)

Sorry...too much to look through. Can you list all your mods and if you have a tune or not?

Satchmo

cliffnotes:

rattling noise at low rpm (1200-1500rpm). Happened whether or not i was in gear or moving so narrowed down to exhaust. checked everything, turned out to be the catalytic convertors. Both were from stainless works (i believe random technology actually makes them for them).

The inside of them had broken loose and slides back and forth, the welds are busted and no real way to fix them.

Car - engine is 100% stock, new era cold air intake, stainless works headers, 160 degree thermostat. Tuned for lean operation (less agressive/better gas mileage) and dyno'd 353 to the back wheels on a dynojet.

I bought the car tuned (it was tuned by a shop in north carolina). I have done nothing to the car except drive it about 3000miles. This is the only issue i've had was the cats.

I also have no idea if they were like this when i bought it, not like i banged on them with a hammer. They weren't making the rattling noise when i got it though and actually the drivers side cat doesnt make noise (yet) it was primarily the passenger side one doing all the rattling.

No other mods currently

Satchmo

Also the roads around here in MI are VERY bad and i go over speedbumps at work (mind you very slowly) at least twice a day, 4 times a day if i go out for lunch. So wondering if it might have just been something jostling loose as well.

Maybe these high flo cats aren't as rugged as oem cats or something