[EuroE92]

So new 335 owner here.

Whenever i started my car in the morning (cold start) I got a rattle noise from my exhaust until the car is warmed up and then the rattle noise goes away.

Thinking something is wrong with the car i brought it into the the dealer and they just called me saying everything with the exhaust is completely fine. They said its common to have that noise cause not enough vaccum pressure goes into the exhaust at a cold start to regulate the system that makes it a dual exhaust during hard acceleration.


So my other 335 owners with stock exhausts do you guys have this issue too or is this BS?

[954Stealth]

Do you still have cat converters on your car?

[EuroE92]

Originally Posted by 954Stealth

Do you still have cat converters on your car?

car is 100% stock so I would say yes

[merchomini]

hmmmmmm.......i wanna say probably b.s.......if it def sounds like a rattle then i wouldnt think anything having to do with vacuum would effect it..... but dont quote me

[954Stealth]

To me it sounds like a bad cat. It's covered under EPA 8/80 warranty, luckily. I'd have them check that; it sounds like they're just being lazy and didn't want to fix something that they have to be reimbursed for at a flat rate.

[EuroE92]

Originally Posted by merchomini

hmmmmmm.......i wanna say probably b.s.......if it def sounds like a rattle then i wouldnt think anything having to do with vacuum would effect it..... but dont quote me

I gave the service guy a hard time when he told me that. I was like i know plently of other people with 335s and they dont do that. And the guy explains to me how the system works, why it does it, and how they tested a few 335s they have in the lot and they all did it.

So IDK. I figure i will ask u guys

[Bronze]

Might be a loose bushing or clamp, or a loose heat shield (and not the exhaust). Can you tell exactly where along the exhaust the rattle is coming from? Near the bumper, or further upstream? Vacuum idea sounds far fetched, but hey, being a dealer, I'm sure they'd prefer to find something to fix.

Hard to argue if they tested other cars on the lot.

[EuroE92]

Originally Posted by 954Stealth

To me it sounds like a bad cat. It's covered under EPA 8/80 warranty, luckily. I'd have them check that; it sounds like they're just being lazy and didn't want to fix something that they have to be reimbursed for at a flat rate.

Thats what i was thinking at first but they did a few other things for me today. I gave them a laundry list of stuff that needed to be fixed or looked at and they did everything else include balancing tires and replacing fuel injectors.

[EuroE92]

Originally Posted by Bronze

Might be a loose bushing or clamp, or a loose heat shield (and not the exhaust). Can you tell exactly where along the exhaust the rattle is coming from? Near the bumper, or further upstream? Vacuum idea sounds far fetched, but hey, being a dealer, I'm sure they'd prefer to find something to fix.

Hard to argue if they tested other cars on the lot.

to me it sounds more by the bumper.

I read a little online and people had the same issue as me and then they did the golf tee mod (which keeps both exhausts open all the time & stops the vaccum stuff) and the noise stopped for them.

[techwhiz]

Panel in the trunk on the drivers side.
Surgical hose clamp on the vacuum line.

That's what I did and it went away. It's the exhaust flap.

[EuroE92]

Originally Posted by techwhiz

Panel in the trunk on the drivers side.
Surgical hose clamp on the vacuum line.

That's what I did and it went away. It's the exhaust flap.

did you throw any lights or error codes?

and i thought it was the plug you needed to unplug to do it.

[BAYsic]

I had the same problem, it was the exhaust flap. Dealer replaced my driver's side muffler under warranty to make it go away. Doing a golf-tee mod will make the problem go away (but not fix it).

[EuroE92]

Originally Posted by BAYsic

I had the same problem, it was the exhaust flap. Dealer replaced my driver's side muffler under warranty to make it go away. Doing a golf-tee mod will make the problem go away (but not fix it).

I did the golf tee mod when i picked up car....

No more noise, car sounds louder

win win

[Spooby713]

Interesting, mine does the same thing and SA gave me some bs story too.

[techwhiz]

Originally Posted by EuroE92

did you throw any lights or error codes?

and i thought it was the plug you needed to unplug to do it.

No codes. Same as golf tee.
Easier to do and can be undone in 30 seconds.

http://www.ebay.com/itm/NEW-TUBING-T...#ht_500wt_1156

Just tie a sting around it so you don't drop it.

[EuroE92]

Originally Posted by techwhiz

No codes. Same as golf tee.
Easier to do and can be undone in 30 seconds.

http://www.ebay.com/itm/NEW-TUBING-T...#ht_500wt_1156

Just tie a sting around it so you don't drop it.

i did the unplug clip thing in the trunk

[E90_boostjunky]

i always hear a weird rattle when i start my car. i had a turbo volvo that did the same thing so i just thought it was normal?

[Bakeme521]

You guys all need to search around, this is a common thing on all 335s. I excuse the OP since he is a new owner, but wastegate rattle upon cold starts is completely normal.

Everyone who made a suggestions, do a little research.

[wobbles1]

Originally Posted by E90_boostjunky

i always hear a weird rattle when i start my car. i had a turbo volvo that did the same thing so i just thought it was normal?

normal: I have even checked brand new cars. it has to do with the warm up phase.

[kblang]

Well I suppose it's good to know it's normal, but I'm sure it still sucks.

[SantaMonica335i]

Happens to me every morning. Lasts for like 30 seconds and then the second exhaust opens up and it goes away. I believe the car keeps one of the exhaust tubes closed to build up heat and pressure when the car is cold. Figure BMW does it for a reason so I've never thought to bypass it and it lasts for such a short period of time. I find the hot restart valve lifter clacking far more irritating from the list of "normal operation" issues.

[BimmerCop]

If the sound is in the back and while starting up cold, it's definitely the exhaust flap activating.