Homelandpatriot

Hey guys, first time poster but I've read the forums for a while.

I have a 2013 GT Premium with a whole list of mods, but my concern at the moment is my exhaust.

I have a full Borla system with XR-1 headers, O/R X Pipe and the S Type catback.

I have had the catback system for about 7 months now and about two months ago decided to take the plunge and go full headers as well. The catback sounded and worked great, but as soon as I added the headers the issues started.

The day I picked it up from the shop there was an immediate metallic rattle sound coming from the car. Never an issue with the car before this and the catback was flawless. I took it to the shop after a few days of hearing this once I decided that this was not normal nor correct. It sounds like a metallic buzzing or extremely fast rattle. The car won't do it at idle or under any kind of revving the engine in neutral, but in gear it starts. If you accelerate very slowly, and I mean super slow and careful, it won't do it. It also won't do it while cruising. Around 2700-3200rpm's under normal driving in all gears, under any acceleration other than super easy it does it, and its real bad under WOT.

I've checked everything from hangers on the mufflers, rear over axle pipe hitting, headers rubbing, heat shields come loose, loose bolts, you name it ive checked it and everything checked out fine.

Ive taken it to two different shops, both time they say they can't find anything and everything has clearance and nothing is shifting. There also aren't any rubbing marks on the pipes.

After all this I got in the engine compartment a couple days ago and really took a good look. I eventually find that two nuts on header bolts had fallen off and are sitting in cutouts in the frame. I take the car back to the shop that installed them and they say they tightened everything back up and everything looks fine. I pick up the car and put it in gear, exact same sound.

So the next day I get to looking at the engine again and while running my hands down the headers feeling for wear spots, my knuckle hits the motor mount bracket nut and it spins freely. I barely touched it. I go to the passenger side and same thing, both nuts are spinning freely, not even finger tight. I tighten the driver's side as best I can (not all that well admittedly, don't have the proper tools to get in there) but I can't get to the passenger side nut with a wrench at all. The nut is currently sitting in my cup holder.

I get in the car after doing a little tightening, same exact fast rattle/metallic buzz sound.

I'm lost on this one. It appears that nothing is touching the exhaust at all and all shields are fine and hangers are no where close, I mean real far from the bracket. I'm taking the car in tomorrow to have the mounts torqued down, but could this be my issue? From everything I've read motor mount make bumping and clunking noises, not rattling.

Any ideas appreciated. I've hit a wall on what to check for

=HYPERDRIVE=

oh wow, I got the same thing happening to me I got the full cat-back S-type Borla, but never bothered to post it up or go to a mechanic to check it. Same fast-"buzz" metal shaking around the cat-xpipe area.
When I did my oil change last week, I checked everything,if its tighten properly, and nothing seams loose. my is automatic, in full auto it doesn't do it that much, but I like to drive in Sport mode most of the time, and change gears manually with the Selectshift What I get is when I accelerate no matter what gear, at precisely 2000rpm, I get the Buzz metal shaking sound, bellow or above 2000 it never happens.
At this point I'm thinking its some kind of "backup" drone effect that makes something around the cats-xpipe shake, who knows what it is.

Brandon302

Could be a bolt hitting the frame or body. I had a similar issue when I tightened one of the cat band clamps with the bolt hitting the frame. Made for an interesting ride for a few miles before I figured out what I had done.

kcoTiger

The sound from up close to the engine might be poorly fitting headers allowing exhaust to escape under throttle. Borla headers don't fit the mustang's block as well as others.

On the sound from the back, it may be from any piece of hardware resting on any part of the drive train or exhaust. Both move and vibrate during motion; possible but not likely is a poor seal somewhere in the exhaust pipes.

steve03gt

If you use metal header gaskets, you can get weird noises as you described if they arent full tight. I don't know what is used on the 5.0s but I know on the diesels I work on we get it.

Homelandpatriot

I got it to the shop today and they spent the day going over everything. They say all the bolts are tight, the exhaust is straight and true and they can't see any issues. They didn't get a chance to drive it yet as traffic is hellacious this time of day in their area but first thing tomorrow morning they will take it out for a drive to see if tightening everything up was the issue.

If not they are gonna take the entire thing apart and start from scratch reinstalling them. I lost faith in the original shop after finding my motor mounts about to fall out of the car after they looked at it TWICE, and this shop has done right by me with everything else Ive taken to them so I expect good work.

I've mentioned these replies to them and they are gonna take a good solid look at it again tomorrow.

Thanks for the help so far and keep any ideas coming.

I'll eventually get some info and pics up of the car. It really is a good beautiful ride, sucks that I have an issue right now.

steve03gt

With the motor mounts being lose, can allow the engine to torque over just a little bit too much allowing contact that may not be easily found when its at rest.. Did they tighten the mounts to the proper torque yet?

Homelandpatriot

So I got my car back from the shop yesterday and they said the motor mounts were worse than I could even tell. Needless to say, they lifted the engine off of them, re-aligned everything, dropped it back down and tightened everything. Thankfully the buzzing is gone. Looks like it was either the mounts themselves from being so loose, or as Steve03gt said, with them being loose the engine was able to move slightly and the headers were coming into light contact with something.

Thanks for all the help guys!

narphenal

Eesh OP, I was thinking about just letting someone else install my headers, but I think I will take care of it just to make sure everything is properly buttoned up.

Ltngdrvr

I'd sure go back to the original knuckleheads and tell them how they screwed up, twice, and tell them they owe you some sort of refund. And if they refuse, trash their rep everywhere you can find to do it.

No excuse for leaving the motor mounts loose the first time, or for not finding it the second time.

narphenal

They should give him a partial refund simply for the inconvenience. Having to go back and forth between a shop is a PITA. Or at least discount another install, etc.

Homelandpatriot

I would take it to a shop if you don't have a lift or are willing to spend a weekend doing this yourself. Just make sure that you take it to someone you really trust.

I was recommended the first shop, and the owner is a big Mustang guy. What I suspect happened is that he didn't do the work personally as I was led to believe would happen, and a regular shop guy without his know how did a slopping job with zero follow through. It looks like they installed the actual headers correctly, they just didn't button everything up correctly afterwards and didn't check their work.

Not fixing the issue the second time around though was unacceptable. Thats when I knew I needed to find another shop. Luckily a group of guys at work at huge high performance muscle car guys and their recommendation for a shop was spot on, I found my new guy for my car.

narphenal

Have two lifts up at work with more than a few people willing to give me a hand if I need it. Glad it is fixed though.

ThrustangFiveO

...and this is why no one touches my car but me. WOW.