Ok for over 6 months now, since as soon as I put on the $200 Hooker catback system, I've had a LOUD, annoying rattle in my system at about 1750-2000 RPM when in gear (hence, I can't track it down because I have to be moving...). The rattle comes from the rear and I dont have cats, so basically you can neglect any possible complications from the front half of the system, but everything is pretty clean as far as I can tell, like the welds and hangers and such. I've had some people tell me that it may just be some "resonant frequency" of the system and that it is natural, but I dont really believe it. Some have said it may be a something loose in the muffler, but its pretty new. What are the chances that this rattle is caused by the gas tank heat shield? If you guys think this is so, what should I do? Some guy on here was gonna take his off and cover it with some dampening material, which I picture as being like spraying it with Line-X or something. What should I use and where can I get it? Thanks guys!

 

it somehow still could be something inside the muffler which is making the noise even though its new. the heat sheild is help in by screws, are any of them loose.

 

I would check to make sure all the screws are in the heat shields. There are 2 pieces of metal back there and a couple of the screws can be hard to get to. It sounds like something is loose. Also you might check your rear license plate, they can make quite a rattle if a screw is loose. Also is the noise more of a buzzing sound?

 

i have a flowmaster force II catback, and it rattles a little in a certain rpm range, and it rattles quite a bit when you rev it in park or neutral and the rpms are falling back down. it seems to be caused by the muffler or something...nothing really looks wrong with it, and i dont think anything is loose inside there. i guess some catbacks just do this

 

i have the same problem at 1450 rpm, due to the tone of the rattle "high pitched and tinny", i know this is a heat shield issue. i have been looking and tightening for 6 weeks and still haven't found it.

once you can identify which shield it is, you can change the resonant frequency of the shield by introducing a small deformation "dent".

the problem is finding which shield as i believe there are 2 or 3 different shields from the shaft on back.

btw...mine is the factory exhaust and in mint condition.

MD350
Formula 350

 

No its definitely a loud rattle, not tinny at all, like a normal exhaust tone, kind of low, but REALLY LOUD, which wouldnt suprise me if it was in high rpms, but its unnatural for it to sound so loud at 2000 rpm even when i've barely got my foot down.

 

My approxiamately 3 week old Hooker catback makes the same noise in the same basic RPM range. It comes and goes, and sometimes changes pitch a little. I haven't gotten serious about tracking it down yet as I've been working on more important things. Hopefully I will get to it this week. If I figure it out, I'll let you know.

 

Its probably touching the panhard support bar thing, while your car is on the ground crawl under it and see if it is close to, or laying on top of it, this is usually a problem with 3rd gens and 4th gens.

 

You mean where it crosses the axle? If so, its definitely not hitting there, its got plenty of clearance and stiff supports. As for along the driveshaft, which is where i thought the panhard bar was, its possible but i dont think so, i guess i could check but it'll be a while before i get the chance.

 

I just rolled under my car a little while ago and found one sheetmetal screw in the shield over the muffler that had backed out. I added a washer for s&g's and tightened it up. No noise on the test drive. We'll see if it's really gone though...

 

Ok as soon as i get a chance i'll look really closely at the shield. If thats not it, I'm replacing the muffler cuz it would probably be an internal flaw. Thanks. Update me if you think your rattle is really gone Vice.

 

Ok update guys - I took the car home for the weekend and checked it out. I live out in the boondocks so cops werent a problem - I took off the muffler first and drove down the street. The rattle was STILL THERE. I took off the heat shields BRIEFLY and went down the street - STILL THERE.

My dad rode with me around the block and he says its normal, but I really think he's just trying to get me to settle with the noise. It REALLY IS unnatural sounding and fake, especially for low RPMS. I'm starting to worry that it is something internal in my engine that is causing it, but I find it hard to believe and harder to fix.

While underneath the car, after I removed the muffler and heat shield, I banged on the gas tank a couple time. I wouldnt say it shook or was loose, but it wasn't a solid "thud" like I expected, it kind of clanged, as if there was another layer of sheet metal just inside the bottom that could vibrate, or that it was hitting some other thin metal around the tank. What do you think?

After all this, what should I check now? Even though I took off my shields and muffler, my entire piping down to the end of my I-pipe was still in place. Should I suspect them or look toward the engine? Thanks for helping guys!

 

Ok, here's a thought off the top of my head - do you think your tank straps could rattle? Are the pads still between the straps and the tank? Could your fuel lines be making contact with anything? I've had my tank off recently, and I can't think of anything else offhand that I think would make noise.
BTW, my rattle is gone, but I still have another noise that I think sounds like my exhaust is in a bind, like maybe I need to loosen it up and re-hang it. I don't know...

 

Now that you mention it, it seems that maybe one of the straps didnt have its pad correctly placed, but i didnt have time to experiment with it - next chance I get I'll check into it. Where would I look at the fuel lines, like what area do you suspect they'd rattle at? Thanks.

 

Well, if I remember right, there's a pad that the lines rest in on top of the tank. I'm not sure I'd drop the tank to inspect it unless I was desperate or really bored. Look at the lines where they come down from on top of the tank and follow the subframe forward. Other than that, at this point I'm starting to run out of ideas. I'll keep you in mind, though.

 

Thanks a lot buddy

 

I actually have this problem but it's not from my exhaust, it's from my subs in the back. I dunno if it could help but I've pinpointed the rattle on mine and it could be the same thing with yours. It's the very corner of the heat shield. There's nothing supporting it and it can rattle very easily. Here's a pic of the spot I was talking about.

 

Well thanks for the input, but unfortunately I had the shield off and tested it and the rattle was still there, so its not the shield. Thanks anyway, though.

 

It may be a chunk of the cat. too big to pass thru the pipe and small enough the rattle inside, go to the exhaust tip, if there's a sight of greyish or ivory colored powder inside the tip. it's the cat.

 

Sorry, I forgot to mention that I dont' have any cats. Any more suggestions? Is there anything that the engine could be doing to produce the noise?

 

Are you sure it is a rattle from outside the exhaust and not a rasp from inside the exhaust? Does it sound like a bunch of rocks inside a trash can being shaken? If so, it may be detonation inside the exhaust. That was the problem I had. The problem turned out to be poor ignition. I replaced the cap, coil(accel supercoil) and rotor and the problem went away. The problem didn't start until I installed my exhaust. Maybe because up the free flowing exhaust it no longer muffled the detonation sound. Who knows. Just something to consider.

 

You know, I think you may be absolutely right with that one. I've got poor ignition and I'm about to revamp the whole thing, from coil to distributor, plugs and all that. Hopefully that will fix the problem then. I just hope it doesnt turn out to be a problem inherent to the way my engine is set up. Thanks!

 

Now that I think of it, I do need at least a cap and rotor. I wouldn't have thought of that. Thanks.

 

I went to the shop today cause I had my new exhaust installed last week and there was a slight rattling, almost like a chirping sound. It was really bad at low rpms especially if I'm on an incline, so we drove it around for a bit and looked underneath. It was actually the exhaust pipe running up over the back axle. It was so small I dunno how we found it. There's a little metal piece kinda like a soda can cut in half at the peak of the bend over the axle. I believe it covers the gas tank and isn't attached to the heat shield itself. It was rubbing against the pipe causing this chirping sound. So we just took a screwdriver and bent it up a little. You think this may be it?

 

I'm not sure what you're talking about but I'm pretty sure I don't have it. thanks though.

 

I've got lots of room there. But thanks.

 

OK, now I really believe I found my vibration, and I'd suggest looking at this if yours isn't fixed.
My problem was the hanger at the I-pipe. Don't know about your system, but mine came with a welded on hanger with two holes drilled in it, one on top of the other. It doesn't readily fit the rubberized piece from the original system without an "L" bracket, which was not supplied. I found a leftover piece from another Hooker system I had that was usable. Mine was making contact between the rubberized factory part and the bolted on L-bracket at the bolt-head. I moved it right before leaving on a 450-mile weekend road-trip. I've heard it rattle, but not near as often. I need to work on it some more, but I'm sure that I've found it this time, as I was able to catch it in the act and stop it by physically moving it by hand.
Sorry for the long post, but hopefully this will help.

 

K thanks, but I'm pretty sure that's not my problem - it is welded to the pipe solid. I'm pursuing the idea that it could be unburnt fuel combusting in the exhaust, which would mean my PROM is not giving the right amount of gas, which I already suspected it wasnt the stock programming because I get knock when I shouldnt as well (too much timing in chip). I'm trying to get someone to burn a simple stock chip for me so I can try that. Does make sense? It doesnt really matter, I want the stock programming anyway, but I was wanting to see if it could possible fix my rattle and knock problems.