Rattling after AMS catted DP install (Update...)

[F12M6MD]

Hey everyone,

I had the AMS catted downpipes installed on my 2013 M6 Coupe back in August. Immediately after I noticed a new rattling noise. This has been discussed on these F10/F12/13 forums in great detail (lead by Hunter). I had the exhaust brackets replaced shortly after provided free by AMS. This fixed some members rattling but not mine. The shop that installed the DP's thought it could be a wastegate issue (as had been documented in the N54 engine in the past) but no way to know for sure. No CEL, no drivetrain malfunction, no loss in power. Just the rattling on deceleration and also near idle.

Well I finally had time to have this re-investigated by a different shop that does Ferrari/Lambo etc. At first, they banged on all parts of the heat shields, along the exhaust under the car and finally came to a rattling "Meisterschaft" nameplate GtHaus uses on their exhaust. It had partially loosened from its welding. I said wow, what an easy fix. We just took it off. Started the car...dang, the rattling still there. They tightened all the bolts on the underbelly. They didn't give up...disassemby began all the way down to the DP's. An hour later, they had found potentially some looser than desired bolts and the DP-turbo bracket on the left was slightly malaligned so they adjusted it. Replaced all heat shielded with care, made sure everything was tight (basically like a full DP install without removing the DP's). Everyone was feeling good about everything....started car, rev'd, and don't you know....rattle still there.

I then took one of the techs on a fun ride to show the rattling. He confirmed. Ruled out the brakes. Didn't sound wastegate related to him. Pulled back in shop and the techs put their heads together and concluded he was "200% sure" it was a loose or damaged cat inside one of the DP's. I called AMS and am waiting to see if they will warranty the DP's for me. We didn't want to spend another 2 hours removing the AMS DP's for lack of time and lack of replacement or stock DP's (in storage). So if anyone is having any rattling in their AMS catted setup, it very well may be poorly manufactured catted DP. I cannot confirm this 100% until I get a replacement pair to plug in and see. I hope AMS comes through for me on this one so we can squash this AMS related rattling issue. Thanks for everyone's input.

Mark

[templarklimek]

Thank you for posting, insightful and very good info. Please let us know. Was this in Houston?

[F12M6MD]

Briefly, let me retract a little bit. Spoke with AMS. Great support. Will be assisting me in getting this resolved whether it's a rare cat problem or wastegate issue. They have not yet had a cat fail so suspicion is very low but at least the cards are on the table and we can continue to find a solution. I'll keep u guys posted.

Mark

[Hunter5179]

Awesome. Keep us posted... AMS is great and have really good customer relationships. I'm sure it will be resolved.

[F12M6MD]

Update...

Dropped M6 off at BMW today. Shop foreman confirmed problem with wastegate by listening. They will give me a more accurate diagnosis and plan later today but he said it could be a few things...pinched vacuum line, actuator problem, mechanically loose wastegate....he said solution could be easy or I could need new turbos. He would have to get approval through BMW for these different options. So far my DP's haven't risen any eyebrows or warranty concerns. I'll update more when I know. I asked if he thought it could cause some power loss if waste gate was not seating properly and he confirmed. Might be a reason why my stock Mustang dyno whp was in the 460's. He said he will be able to check boost pressures, etc.

Mark

[Hunter5179]

Originally Posted by F12M6MD

Update...

Dropped M6 off at BMW today. Shop foreman confirmed problem with wastegate by listening. They will give me a more accurate diagnosis and plan later today but he said it could be a few things...pinched vacuum line, actuator problem, mechanically loose wastegate....he said solution could be easy or I could need new turbos. He would have to get approval through BMW for these different options. So far my DP's haven't risen any eyebrows or warranty concerns. I'll update more when I know. I asked if he thought it could cause some power loss if waste gate was not seating properly and he confirmed. Might be a reason why my stock Mustang dyno whp was in the 460's. He said he will be able to check boost pressures, etc.

Mark

Nice, another forum member named luigimaster actually went through all this himself. His SA told him the same thing and he changed out everything you stated and he still had the problem. I hope yours gets fixed going this route because if not it will just bring more heat down from bmw and make them more suspicious of modders. Keep us posted. Thanks

[AlphaAlpineM6]

I don't think it's a damaged catalytic converter. I've noticed catless downpipes have similar issues. Including mine. There's a fix for this.

[AlphaAlpineM6]

Originally Posted by F12M6MD

Update...

Dropped M6 off at BMW today. Shop foreman confirmed problem with wastegate by listening. They will give me a more accurate diagnosis and plan later today but he said it could be a few things...pinched vacuum line, actuator problem, mechanically loose wastegate....he said solution could be easy or I could need new turbos. He would have to get approval through BMW for these different options. So far my DP's haven't risen any eyebrows or warranty concerns. I'll update more when I know. I asked if he thought it could cause some power loss if waste gate was not seating properly and he confirmed. Might be a reason why my stock Mustang dyno whp was in the 460's. He said he will be able to check boost pressures, etc.

Mark

I've noticed I boost 16.1 WOT in power-band and 18.1 WOT out of power-band. Log your boost see if you see a marginal difference.

[boots]

Glad your getting it fixed mark. I should be back in town at the end of this week. You should take a ride in my car to see the difference in dp.

[F12M6MD]

Another update:

Got call from SA at BMW dealer...they found a fault in a mechanism that helps control vacuum pressure which should normally hold the wastegate closed tightly immediately after opening. They also replaced a vacuum hose. It appears the problem is on the passenger side. Got the call right near closing that I could grab my car and that it was resolved. Jumped in loaner, made the exchange, started my car, and guess what?...the same damn rattle is still there. I immediately got out, told them, they grabbed foreman/mechanic that worked on issue. He listened to it and said yep it's not fixed. I got to talking with the guy as they worked on getting me back my loaner and he is kinda stumped on why it didn't fix the rattle. They will continue to work on solution tomorrow. Despite not fixing the problem, I'll give this dealership props on helping me at and after closing time. Again, I will give you all an update when I have one. Thanks for everyone's input and concern.

Mark

Re: DP cat being loose...I agree that it can't be that.

Re: boost pressure...they did not report it to me but I'll try to get those #'s.

Re: Boots... Yeah I'd like to hear yours for sure. Holla when you're in town.

[boots]

Cool. What dealership is service your car. One SA at katy is friendly to mods as well.

[AlphaAlpineM6]

There's nothing wrong with your car... stop wasting your time. The noise is normal across the board with cars with aftermarket cats.

[gmd2003]

Originally Posted by AlphaAlpineM6

There's nothing wrong with your car... stop wasting your time. The noise is normal across the board with cars with aftermarket cats.

Actually not all . My Supersprints have 0 rattle, and the Noelle one based off the stock dont either . You get what you pay for .
George

[Hunter5179]

What happened? Any new updates

[Ameer ///M6]

keep us updated bro.

[JoeyLeeBMW]

The only solution to this issue to is go with CATLESS AMS DOWNPIPES!