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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Rattle and hum



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      06-22-2018, 09:18 PM   #1
Bimmer_Engineer
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Rattle and hum

So I have this metallic rattle that I hear from the drivers side exhaust pipe. It let for about 1-2 seconds immediately after start up and then disappears...any ideas on what that is?

Thereís not really a him by the way...that was just an unrelated u2 reference...
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      06-22-2018, 09:51 PM   #2
Emilime75
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Exhaust flap in the driver's side muffler, it's common. Look up "golf tee mod", but don't bother with it...in your trunk, there's a connector under the driver's side tail light, un plug it, it's for the flap actuator. This will keep it open always and not rattle anymore.
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      06-22-2018, 09:54 PM   #3
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Thx bud...
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      06-23-2018, 12:40 AM   #4
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You put in downpipes recently? That could cause rattle and hum.... U2 ftw
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      06-23-2018, 06:32 AM   #5
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Negative on the downpipe...I think itís the exhaust flap...will disable this morning and see if it goes away...

Btw...I just unplugged the actuator for the valve...omg that sounds good!

Edit: I read an thread about unplugging the acuator and I saw several owners reporting popping off vacuum hoses after disabling the valve. Iíve got to go to the dealership on Tuesday for the blower motor recall...Iíll do this again after I get my car back. In the meantime...any kind of a general assessment as to how many people had vacuum issues associated with this valve? It looked like they were in the minority...

Last edited by Bimmer_Engineer; 06-23-2018 at 07:18 AM.
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      06-23-2018, 07:24 AM   #6
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Have not heard of that.
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      06-23-2018, 07:55 AM   #7
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http://www.e90post.com/forums/showthread.php?t=80661

Thereís 2 people at the end of this thread that had issues after the unplugged the acutuator. It might be unrelated but Iím just gonna wait till I get the car back from the dealer and then do the golf tee mod...
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      06-23-2018, 08:56 AM   #8
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2010 BMW 335xi  [0.00]
Quote:
Originally Posted by Bimmer_Engineer View Post
http://www.e90post.com/forums/showthread.php?t=80661

Thereís 2 people at the end of this thread that had issues after the unplugged the acutuator. It might be unrelated but Iím just gonna wait till I get the car back from the dealer and then do the golf tee mod...
I had the issue when I first got my car. Did the actual golf tee mod and it went away. Should be fine once you do that.
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      06-23-2018, 09:07 AM   #9
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It's fine if you want to wait if it makes you feel better, but let's ease your worries...

Just read the last page of that thread...the 2 issues people had were with 2 very common problems these engines have, and I'm 99.99999999% sure they were coincidental.

The plastic OEM charge pipe is known to crack often, and that's why there are so many metal/aluminum aftermarket offerings for them, as there is no performance benefit from replacing them, only reliability. This should almost be part of a preventative maintenance program, it's that common, and for sure if any performance mods are done/planned. When it does crack, one would be a fool to replace it with an OEM part.

The vacuum lines get brittle and crack with age, on any car, but on the N54 the problem is accelerated due to the high temp these engines operate in. Replacing these lines should be a preventative maintenance item, and most who do, choose silicone lines to replace them with as they are tolerant of higher temps and last longer. They are cheap and easy to do, only hard parts are the 2 turbo waste gate actuators, but do-able.

Furthermore, there is a vacuum line under the hood leading to the driver's side fender area...this is the line that runs back to the flap actuator which is opened/closed by a solenoid(what you're disconnecting in the trunk), and the solenoid controls vacuum applied to the flap. Some, when replacing their vacuum lines, leave that line disconnected and plug the port to seal it, as it is no longer necessary. Think of it this way, it's similar to your kitchen faucet, except that the faucet is under pressure, and the exhaust flap is under vacuum...

Water comes in to the house/vacuum is being made by the engine, both are always there.

Your kitchen faucet is a valve/the exhaust flap actuator is a valve.

Your kitchen faucet(valve) is being controlled (opened/closed) by your hand/the exhaust flap actuator is being controlled by the solenoid.

Your brain decides when to open/close the faucet/the car's DME decides when to open/close the flap.

The DME does not communicate with the solenoid, except to tell it to open/close, but has no clue if it is/not actually doing it's job.
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      06-23-2018, 09:28 AM   #10
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Agreed...Iím an engineer and Iím typically sensible and logical. That said I need the car to be drivable on Tuesday so it can go to the dealer and reading this forum will give almost anyone a reliability complex with these engines...
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