[PASE624]

Hey all

I have a 2020 M2C (8000 miles) with primary (dp) cat delete, secondary cat delete, and resonator delete, as well. I had the work done last Monday and everything was fine. However, 4 days after, on Friday, my car started to rattle from the exhaust. heres the symptom...

Rattle is only during comfort mode between 1500 to 2000 rpm, at any gears, 1 through 7.

Rattle is not present during sport or sport plus mode, basically when the flaps are open.

No rattling during cold start, regular start, idling, revving when stationary, etc.

I have bm3 stg2 flash on it and this Never Ever happened before. Will putting back at least the resonator fix this problem? what can be the issue?

Any help/tips/ advice/ solution will be greatly appreciated. Thank you in advance, everyone.

[Got f1?]

Originally Posted by PASE624

Hey all

I have a 2020 M2C (8000 miles) with primary (dp) cat delete, secondary cat delete, and resonator delete, as well. I had the work done last Monday and everything was fine. However, 4 days after, on Friday, my car started to rattle from the exhaust. heres the symptom...

Rattle is only during comfort mode between 1500 to 2000 rpm, at any gears, 1 through 7.

Rattle is not present during sport or sport plus mode, basically when the flaps are open.

No rattling during cold start, regular start, idling, revving when stationary, etc.

I have bm3 stg2 flash on it and this Never Ever happened before. Will putting back at least the resonator fix this problem? what can be the issue?

Any help/tips/ advice/ solution will be greatly appreciated. Thank you in advance, everyone.

Strictly a guess since I haven't done this mod, but could the flap actuators be loose and it manifests only when in closed?

[PASE624]

no. if it was loose, then it would rattle at all times...eco, sport, and sport plus...
thas why its driving me nuts and i have no one but forim ppl to ask for help. mechanics, service center, etc...lost cause

[Got f1?]

Originally Posted by PASE624

no. if it was loose, then it would rattle at all times...eco, sport, and sport plus...
thas why its driving me nuts and i have no one but forim ppl to ask for help. mechanics, service center, etc...lost cause

I was thinking it rattles only at a certain point, in this case when valve is closed. Just a guess. It has to be tied to something since it is not consistant.

[chmura]

Unfortunately you have to do some diagnosis on your own. Jack up your car and start hitting the exhaust in various places with your fist until you hear a rattle.

[cecaa850]

You said that you had the work done for you. Couldn't you just bring it back to them and have it checked?

[m2cWW]

Yo! Had the same issue. Check two things, one is the screw that holds itself onto the U bracket under the car (under the passenger side seat more or less). Two, check for internal rattle. Particularly, squeeze the big piece of plastic by your rear view mirror while doing that and see if that changes anything. Good luck man!!

[msdss]

good luck tracking it down. my stock exhaust rattles whenever I turn the car on. it has ever since I bought it. Brand new, 0 miles. rattles. sucks.

[FreeDarko]

Search Tommy L video on this.

Check if they reused the old part when installing the exhaust.

[hlm2c]

The two places I would check are:

1) Chassis brace - If you exhaust has been modified, double check the clearance room in between the mid-pipe and the chassis brace. Exhausts will vibrate and flex on idle and under throttle which can result in your mid-pipe rubbing against the chassis brace due to the tight space from factory. Adding washers in between the chassis brace screws can help improve clearance. An alternative method as well is that AA sells an aftermarket chassis brace with a slight dip in the middle to improve clearance between their mid-pipe and the chassis brace, which you could probably buy separately. Check the underside of your mid-pipe too to see if there are any rub marks to see if that could hint to this being the culprit. If it's rattles, this would be more likely than the next suggestion.

2) Exhaust gaskets from DP to mid-pipe and/or turbo to DP. These are designed to be one time use and are crushed in the process to form a seal whenever you attach DP to any of the adjacent components. Usually this is more for leaks though, although a poor seal could still lead to rattles.

And just double check all the bolts are still on tightly as well. After modifying your exhaust and re-bolting them back up, it's good practice to go under your car and double check after you've driven around in it after a while.

[FreeDarko]

Originally Posted by hlm2c

The two places I would check are:

1) Chassis brace - If you exhaust has been modified, double check the clearance room in between the mid-pipe and the chassis brace. Exhausts will vibrate and flex on idle and under throttle which can result in your mid-pipe rubbing against the chassis brace due to the tight space from factory. Adding washers in between the chassis brace screws can help improve clearance. An alternative method as well is that AA sells an aftermarket chassis brace with a slight dip in the middle to improve clearance between their mid-pipe and the chassis brace, which you could probably buy separately. Check the underside of your mid-pipe too to see if there are any rub marks to see if that could hint to this being the culprit. If it's rattles, this would be more likely than the next suggestion.

2) Exhaust gaskets from DP to mid-pipe and/or turbo to DP. These are designed to be one time use and are crushed in the process to form a seal whenever you attach DP to any of the adjacent components. Usually this is more for leaks though, although a poor seal could still lead to rattles.

And just double check all the bolts are still on tightly as well. After modifying your exhaust and re-bolting them back up, it's good practice to go under your car and double check after you've driven around in it after a while.

I believe these gaskets are what Tommy L was referring to.

Anyone know the part number?

[hlm2c]

Originally Posted by freedarko

i believe these gaskets are what tommy l was referring to.

Anyone know the part number?

18-30-7-851-168

[mshea397]

I have the same config as you do (downpipes, AA midpipe, BM3) and had the exact same issue. I disassembled and reassembled the exhaust 3 time making sure to very carefully check clearances (adjusting the downpipes to optimize the angle of the mid-pipe). Overall, a pain in the ass, but now it is 90% better. There is a very slight vibration in efficiency mode in low RPM. So far, not enough of an annoyance to do it again and to some of the other posts, I think it might be something other than the exhaust at this point.

[PASE624]

Update.

Rattle fixed. I put the resonator back on and everything is all good. primary and secondary cats are gone. I didnt know a resonator will cause a tin can flap rattle at low rpm in comfort. you learn something new everyday. rattle gone