Need help diagnosing exhaust rattle noise

[seely]

Have a 2019 mustang GT 6speed with a Roush supercharger

Been hearing a noise since the supercharger install coming from under the car. Sounds like sheet metal vibrating/rattling/buzzing, its hard to describe. It's audible when I'm driving next to a car or wall because it starts echoing off those. I'll try to upload a video soon.

Have no idea if its the cats, but that's where I'm starting...

• haven't seen any codes I can check again
• no check engine light
• haven't had a chance to look under the car at the exhaust for holes or while its running

1. Is the test to do to drill a hole and check the pressure? '
2. Are they easy to replace?
3. How else could I check?

I never scrape the bottom of the car. When had it towed once the car rolled off the bed about 7 inches off the ground, which was enough to bend the pinch weld around the jack points. Didn't see any apparent issues with exhaust after that though. If that did any damage I'd assume there's an exhaust leak or something. Not sure how to check for that either.

What else should I start checking?

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[MidnightStars]

Definitely requires your eyes to check it out.
When you lift your car, check for:

• Loosened bolts/broken or misshaped hangar for the catback
• Any stray part or debris that seems too close to the exhaust
• Unusual play all along exhaust

If all that checks out, start the car. Use your hands to feel for vibrations in areas of the exhaust that are higher than any other parts. See if the exhaust comes into contact with anything as they vibrate.

If all that is still fine, try holding the revs at 2.5k or even 3k, and repeat. You will more than likely need some heat resistant gloves at that point.

And even after that, there's no issue, it's probably your cats.

 

[seely]

Definitely requires your eyes to check it out.
When you lift your car, check for:

• Loosened bolts/broken or misshaped hangar for the catback
• Any stray part or debris that seems too close to the exhaust
• Unusual play all along exhaust

If all that checks out, start the car. Use your hands to feel for vibrations in areas of the exhaust that are higher than any other parts. See if the exhaust comes into contact with anything as they vibrate.

If all that is still fine, try holding the revs at 2.5k or even 3k, and repeat. You will more than likely need some heat resistant gloves at that point.

And even after that, there's no issue, it's probably your cats.

Do you know if its a common issue for the cats to go bad after adding a Roush blower? Maybe more of a question for the forced-induction threads, but its on my mind.


I'd need two people for this I guess + I don't have a lift. I'll have to wait to bring it some where to take a look.

 

[AZ18yote]

Do you know if its a common issue for the cats to go bad after adding a Roush blower?

If you check the monster Roush thread you will see more than a handful of guys that had their cats replaced under warranty. Not sure how to qualify common but definitely enough to make note of.

 

[seely]

If you check the monster Roush thread you will see more than a handful of guys that had their cats replaced under warranty. Not sure how to qualify common but definitely enough to make note of.

I'm in that thread but TBH not browsing the pages since there's so many. Thanks for the info.

Not sure if theres a way to search for keywords within a thread?

 

[MidnightStars]

Do you know if its a common issue for the cats to go bad after adding a Roush blower? Maybe more of a question for the forced-induction threads, but its on my mind.


I'd need two people for this I guess + I don't have a lift. I'll have to wait to bring it some where to take a look.

If it is bad cats, and you don't smell anything bad, or get poor performance or codes, you're probably lucky and the honeycomb just seems to maintain its orientation to let proper flow through.

And you sure don't seem alone on the matter: https://www.mustang6g.com/forums/threads/catalytic-converter-replaced-at-8300-miles.123393/

Other users have suggested moving away from OEM cats as well: https://www.mustang6g.com/forums/threads/e85-and-cats-keep-or-delete-help.150802/

If you'd like to check soon, the bare minimum is a set of jack + jackstands

 

[MidnightStars]

I'm in that thread but TBH not browsing the pages since there's so many. Thanks for the info.

Not sure if theres a way to search for keywords within a thread?

Very easy to look up. Go to Google, type: insite:mustang6g.com cats
Literally the first result:

 

[seely]

If it is bad cats, and you don't smell anything bad, or get poor performance or codes, you're probably lucky and the honeycomb just seems to maintain its orientation to let proper flow through.

And you sure don't seem alone on the matter: https://www.mustang6g.com/forums/threads/catalytic-converter-replaced-at-8300-miles.123393/

Other users have suggested moving away from OEM cats as well: https://www.mustang6g.com/forums/threads/e85-and-cats-keep-or-delete-help.150802/

If you'd like to check soon, the bare minimum is a set of jack + jackstands

Right on sorry my forum search skills are crappy.

Yeah I'll read these threads to see other's symptoms.

Tbh I was thinking of lifting it up tonight. Just don't think i'll see anything but lets see what these threads say.

 

[seely]

Yeah not good a googling either tbh... cant ever find what i'm looking for

 

[MidnightStars]

Yeah not good a googling either tbh... cant ever find what i'm looking for

I'm in the same boat, it happens.
When I have my own problems, I can't find it in the forums, or on Google. But the moment I make a thread on it, I can suddenly find the answers just about everywhere

 

[seely]

I'm in the same boat, it happens.
When I have my own problems, I can't find it in the forums, or on Google. But the moment I make a thread on it, I can suddenly find the answers just about everywhere

Right thought I was brought up in the right generation but still can't use technology Lol.

Thanks for the help. Hoping now to find some setup to run with the blower without going too loud. Honestly I have too loud things that I drive, the mustang is relatively quiet and relaxed imo. But I'll be running E85 soon and it looks like most people are recommending to ditch the cats when running E85. I have a couple parts otw

 

[5ohmatt]

Have a 2019 mustang GT 6speed with a Roush supercharger

Been hearing a noise since the supercharger install coming from under the car. Sounds like sheet metal vibrating/rattling/buzzing, its hard to describe. It's audible when I'm driving next to a car or wall because it starts echoing off those. I'll try to upload a video soon.

Have no idea if its the cats, but that's where I'm starting...

• haven't seen any codes I can check again
• no check engine light
• haven't had a chance to look under the car at the exhaust for holes or while its running

1. Is the test to do to drill a hole and check the pressure? '
2. Are they easy to replace?
3. How else could I check?

I never scrape the bottom of the car. When had it towed once the car rolled off the bed about 7 inches off the ground, which was enough to bend the pinch weld around the jack points. Didn't see any apparent issues with exhaust after that though. If that did any damage I'd assume there's an exhaust leak or something. Not sure how to check for that either.

What else should I start checking?

I would assume it is your cats if you still have them on the car. I am catless and ran into the same problem and came to find out it was my mufflers, I blew them out and they would rattle, and shake, easy fix I just went X pipe into turn downs.

 

[seely]

I would assume it is your cats if you still have them on the car. I am catless and ran into the same problem and came to find out it was my mufflers, I blew them out and they would rattle, and shake, easy fix I just went X pipe into turn downs.

Whats your catless exhaust system setup?

Someone for lethal performance is telling me "With the 15+ Mustangs, they built 1 cat into the manifolds" Is that true?

If you heard the sound would you be able to identify it again? I'm thinking about making a video soon. What was the rattling sound you were hearing like?

 

[Cobra Jet]

Have a 2019 mustang GT 6speed with a Roush supercharger

Been hearing a noise since the supercharger install coming from under the car. Sounds like sheet metal vibrating/rattling/buzzing, its hard to describe. It's audible when I'm driving next to a car or wall because it starts echoing off those. I'll try to upload a video soon.

Have no idea if its the cats, but that's where I'm starting...

• haven't seen any codes I can check again
• no check engine light
• haven't had a chance to look under the car at the exhaust for holes or while its running

1. Is the test to do to drill a hole and check the pressure? '
2. Are they easy to replace?
3. How else could I check?

I never scrape the bottom of the car. When had it towed once the car rolled off the bed about 7 inches off the ground, which was enough to bend the pinch weld around the jack points. Didn't see any apparent issues with exhaust after that though. If that did any damage I'd assume there's an exhaust leak or something. Not sure how to check for that either.

What else should I start checking?

Aside from the cats being a possibility…. I literally just posted the below info in another thread, but some of it might help you with your concerns and diagnosis…

I’d check the following:

Check the trans block spacer plate, it’s a common issue across the S550 and F150 platform:
https://www.mustang6g.com/forums/threads/engine-transmission-plate-noise-fix.115718/

https://www.mustang6g.com/forums/th...hen-accelerating-hard-above-4000k-rpm.107728/

Check the emergency brake cable and attaching assembly found under the driver side trans tunnel. This has been a known source of metallic rattle as well and is hard to replicate unless in a certain RPM range. The cable is loose and raps against the trans tunnel under certain conditions OR could be touching exhaust mid pipe. How to adjust the cable and assembly:
https://www.mustang6g.com/forums/threads/how-to-adjust-your-parking-brake.25204/

If looking at both the e-brake and spacer plate from under the car, yes visually they will look “fine”, but take a closer look to make sure both are not a source of the rattle.

Check the driveshaft center support bearing assembly. There is a small aluminum plate attached to the bottom of it which comes loose and rattles - see this thread:
https://www.mustang6g.com/forums/threads/identify-this-metallic-rattle-.161210/#post-3455184

If equipped with MT82, check this thread for the source of clunk/rattle coming from passenger side or under car:
https://www.mustang6g.com/forums/threads/found-source-of-clunk.133988/#post-3309826

Also check the exhaust piping from front to back to make sure the piping is not coming in contact with the body (trans tunnel, floor pans, trans mount, etc) and check all clamps too to also make sure those are secure and not rubbing on anything.

 

[seely]

Aside from the cats being a possibility…. I literally just posted the below info in another thread, but some of it might help you with your concerns and diagnosis…

I’d check the following:

Check the trans block spacer plate, it’s a common issue across the S550 and F150 platform:
https://www.mustang6g.com/forums/threads/engine-transmission-plate-noise-fix.115718/

https://www.mustang6g.com/forums/th...hen-accelerating-hard-above-4000k-rpm.107728/

Check the emergency brake cable and attaching assembly found under the driver side trans tunnel. This has been a known source of metallic rattle as well and is hard to replicate unless in a certain RPM range. The cable is loose and raps against the trans tunnel under certain conditions OR could be touching exhaust mid pipe. How to adjust the cable and assembly:
https://www.mustang6g.com/forums/threads/how-to-adjust-your-parking-brake.25204/

If looking at both the e-brake and spacer plate from under the car, yes visually they will look “fine”, but take a closer look to make sure both are not a source of the rattle.

Check the driveshaft center support bearing assembly. There is a small aluminum plate attached to the bottom of it which comes loose and rattles - see this thread:
https://www.mustang6g.com/forums/threads/identify-this-metallic-rattle-.161210/#post-3455184

If equipped with MT82, check this thread for the source of clunk/rattle coming from passenger side or under car:
https://www.mustang6g.com/forums/threads/found-source-of-clunk.133988/#post-3309826

Also check the exhaust piping from front to back to make sure the piping is not coming in contact with the body (trans tunnel, floor pans, trans mount, etc) and check all clamps too to also make sure those are secure and not rubbing on anything.

Awesome thanks for these troubleshooting steps! Even if theres no issue its good to go through. The "metal raspy" or "plastic bag" sound descriptions definitely are in the ball park of what i'm hearing. For a second I thought it sounded like air sucking in.. assumed it was like the air intake or something .. but its not really an air intake sound? IDK i hate subtle issues like these they drive people like me (who must have everything dialed in) crazy

And to be clear I was not saying it was definitely the cats. It was just one place i wanted to look at since it seems to be a common issue according to a good number of people. Common issue especially after supercharging.

Another thing i want to note, I realized I could just "test" the cats by taking off the cat back exhaust piece and basically looking into them for visual inspection.


Update:

I just took the car for a drive for a good 45 min. Tried to record it and couldn't really get the sound captured. Rev'd it a bunch of times in my driveway with the door open and it didn't really sound like anything coming from the front of the car or under.

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