Rattle after I installed exhaust

[knelson]

Well a simple bolt on project ended up being a huge pain in the butt today. I went to install the infiniti sports exhaust which is just a muffler and exhaust tip swap with the stock. And while I'm in Texas, the car spent two years in New Jersey and there's rust underneath in some areas. The bolts holding the exhaust pipe to the muffler were seized so I fought with them for hours. I eventually had to cut one bolt out. Finally I got both sides almost finished. (Besides now they aren't even and I need to do some adjusting tomorrow, although even this was a nuisance because they were factory specs, used the same hangers and everything, but after installing they aren't the same height.)

My question is, now I'm getting a rattle from the middle of the car... seems like under the drivers seat. And the rattle is only when there's. Load on the engine... not in park, but under light acceleration. I'm wondering if as I was cutting, or more likely hitting with a screwdriver and hammer on the back driver side to break the really problematic bolt, could I have knocked something loose all the way up toward the cats?

Any thoughts?

I'll get back out there tomorrow and investigate. But I'm not sure I can figure this one out without a lift, I might have to go to a muffler shop to help me diagnose.

[Ilya]

I was gonna say maybe a grommet or something came loose, but if it's that much farther up front I'm not sure...

[armybrat]

I installed the sport mufflers as well as a whole new X-pipe and duals from the manifolds back myself. Floor jack should be plenty high enough to troubleshoot any issues. I could see pretty much everything when I was doing mine. Yeah the bolts are notorious for rusting out; I wrung my muffler bolts loose plus one of the manifold studs (where the Y-pipe bolts to it) with a long handle 1/2" drive ratchet. There is adjustment in the bolt holes as well as the hanger brackets, so as far as the unevenness goes, you might have to loosen those and adjust the tips to the cutouts in the rear bumper and retighten. Also, the tips themselves are adjustable. Mine centered up nicely but I had to mess with it some to get the look I wanted. My mufflers were slightly canted so I had to turn the tips in the opposite direction to get the slants to line up horizontal. If the rest of your exhaust is stock the rattle could be coming from the heat shields around the front Y-pipe if you think it's under the driver's seat. I would also check the tunnel heat shields and metal shields by the mufflers as well.

[knelson]

I think it actually IS related to the fact that I jacked up the car to install he exhaust only on the rear driver side. I didn't raise it much, maybe the rear driver tire 1.5" off the ground, but it possible twisted the car just enough to loosen something. It's minor, and not consistent, so I have to look again tomorrow.

Kit went on easily besides the rusted bolts, I aligned it and it looks good. I actually think the car is even breathing better although they don't advertise a HP increase with that kit.

[armybrat]

Yeah the sport mufflers are straight through vs stock reverse flow, plus they are lighter weight. As you probably found out, the factory muffs are heavy. I've never had any issues with rattles from just raising the car with a jack, but I can only speak for my car. From what I've seen from folks working underneath the car, most rattles come from the heat shields getting bumped or bent where they're touching part of the frame or other parts, or you could've loosen a spot weld. I know it's aggravating so I hope you find the source of it. Anyway, enjoy the new mufflers!

[knelson]

Good news is that the rattle and noise is so minor it's hard to notice. Bad news, that makes it hard to figure out what it is!

I do think the car instantly is breathing better! Thanks for the info. And yes the older mufflers were twice as heavy as the new ones.

I'll check into the heat shields again, it does sound like it would be related to them... it's got that same pitch of metal rattle that a heat shield would make.