MPE rattlings at cold start, driving around, and reverse

[r0wr]

Recently bought a used 2015 M4 and I didn't know this until the day I came to pick it up but there's an MPE on it! It sounds great but I noticed on cold start and sometimes when driving around and reverse, it'll rattle. I've done some research and some people say it's the butterfly valve. Can anyone confirm from this video below. The rattling occurs right at the beginning and around the 23 second mark. Password is F82.

Also, the AC on the car doesn't work. It was fine when I test drove the car two weeks ago but when I ran it today, nothing but hot air. Seems like this is a known issue.

[SanchoDivine]

Your video is private and can not be viewed.

Start by checking the screws that secure the tips and ensure they are tight. I thought mine were tight at first but it turned out that 1 of them actually needed at least another turn. That resolved my vibration when I first got my MPE.

If not the tips than it could be a bad part on the valves, exhaust hangers with a loose bolt/nut, a bad hanger, a loose heat shield, something touching the heat shield, the ebrake line rattling against the drive shaft (if your car did not already come with it fixed), cracked MPE, or something else. Could be something easy to fix or something that requires help.

Good luck!

[r0wr]

Originally Posted by SanchoDivine

Your video is private and can not be viewed.

Start by checking the screws that secure the tips and ensure they are tight. I thought mine were tight at first but it turned out that 1 of them actually needed at least another turn. That resolved my vibration when I first got my MPE.

If not the tips than it could be a bad part on the valves, exhaust hangers with a loose bolt/nut, a bad hanger, a loose heat shield, something touching the heat shield, the ebrake line rattling against the drive shaft (if your car did not already come with it fixed), cracked MPE, or something else. Could be something easy to fix or something that requires help.

Good luck!

I appreciate your response. The password is F82.

[Brasko]

I was able to view your video using the password you provided. Thanks for sharing. Watched it a couple times, especially the very first part. You can definitely hear the sound you are talking about. My first thoughts are...

1) Doubt it's this, but hold down the license plate and see if it stops. Could just be a light vibration from the frequency of the exhaust note at very low RPM's.

2) Check the MPE tips. Generally below 2000 RPM's most will experience a slight rattle coming from the MPE. This is usually due to a screw that just needs tightening.

Here's a helpful link


If the issue still persists, I'd get the car up on a lift and look for any areas were the exhaust may be touching a heat-shield or something similar.

[r0wr]

Originally Posted by Brasko

I was able to view your video using the password you provided. Thanks for sharing. Watched it a couple times, especially the very first part. You can definitely hear the sound you are talking about. My first thoughts are...

1) Doubt it's this, but hold down the license plate and see if it stops. Could just be a light vibration from the frequency of the exhaust note at very low RPM's.

2) Check the MPE tips. Generally below 2000 RPM's most will experience a slight rattle coming from the MPE. This is usually due to a screw that just needs tightening.

Here's a helpful link


If the issue still persists, I'd get the car up on a lift and look for any areas were the exhaust may be touching a heat-shield or something similar.

Thanks for the link and the suggestion. I will look into these. I'll also be bringing it to the dealership on Monday so hopefully they can figure it out

[Silenus]

I've replaced an MPE muffler for this exact noise, under warranty. Only did it under cold start, VERY loud. I swapped out the Ti tips first, but it changed nothing. After that, had the green light to replace it under warranty.

[damageprone]

I had the same noise on mine. Check the sides of the muffler can to see if there are hairline cracks on the welds where the pipes enter the can. My exhaust was replaced under warranty because of the cracks and the valves were stuck.

[r0wr]

So I brought it into the dealership under warranty and they found 2 cracks on the muffler. It is being replaced in full. I also asked for the emblems on the seats to be replaced as mines were cracked and they did.

I tried to ask if I could pay the difference for CF tips and he said no haha.

[Brasko]

Originally Posted by r0wr

So I brought it into the dealership under warranty and they found 2 cracks on the muffler. It is being replaced in full. I also asked for the emblems on the seats to be replaced as mines were cracked and they did.

I tried to ask if I could pay the difference for CF tips and he said no haha.

Nice! That's great that they replaced it.

[socal619]

You should ask if you can buy the cf tips @ their cost then 😂

[DataNerd]

Is this a cold start with the valves open or closed?

[r0wr]

Originally Posted by DataNerd

Is this a cold start with the valves open or closed?

Closed.

[G35POPPEDMYCHERRY]

Damn that exhaust was about fall off

[DataNerd]

I put the MPE on mine from the dealer. It's never sounded like that. Definitely take it in and see what they say.

[r0wr]

Originally Posted by DataNerd

I put the MPE on mine from the dealer. It's never sounded like that. Definitely take it in and see what they say.

They're replacing it. See post above.

[t5pilot]

An all too common problem. I recently acquired an MPE that had suffered cracking to the silencer sidewall - Common, as it's thin & the pipe joints coming out on either side are the only means of supporting the whole thing.

Although the cracks had been repaired, the 'rattling tin can' sound was still a problem, despite there now being no cracks.

No receipt for the MPE, so had a local fabricator do this for me...

Now there's no flex with the out pipes - And the rattle has been completely eliminated Happy days & £100 to do...

[r0wr]

Originally Posted by t5pilot

An all too common problem. I recently acquired an MPE that had suffered cracking to the silencer sidewall - Common, as it's thin & the pipe joints coming out on either side are the only means of supporting the whole thing.

Although the cracks had been repaired, the 'rattling tin can' sound was still a problem, despite there now being no cracks.

No receipt for the MPE, so had a local fabricator do this for me...

Now there's no flex with the out pipes - And the rattle has been completely eliminated Happy days & £100 to do...

Nice, I'll be sure to note this next time when my new MPE breaks in like two years!

Just received car. I wasn't able to test a true cold start but the rattling is gone at all RPMs. Will test a true cold start tomorrow morning to see if it rattles.

[uniqueMR]

I have same issues with my MPE. Going to dealer soon and have them check it out !!!

[revenlymokalu]

My MPE.
Just gonna leave it as is until it dies.

[damageprone]

Originally Posted by revenlymokalu

My MPE.
Just gonna leave it as is until it dies.

Yikes! Did you at least try to ask the dealer about it? Worth a shot. That doesn't look like an exhaust that lived in CA...more like the salty east coast.

[f80er]

Originally Posted by damageprone

Yikes! Did you at least try to ask the dealer about it? Worth a shot. That doesn't look like an exhaust that lived in CA...more like the salty east coast.

What does it matter where it lived? MPE cracks regardless of its location.

[revenlymokalu]

Originally Posted by damageprone

Yikes! Did you at least try to ask the dealer about it? Worth a shot. That doesn't look like an exhaust that lived in CA...more like the salty east coast.

California. Lol
It's been tampered so dealer can't do anything.
Very unfortunate. I'm gonna put DP and Midpipes combo. Hoping the rattles won't be noticeable.