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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 > What is the rattle?!



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      12-12-2017, 02:25 PM   #1
WatchWolf34
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What is the rattle?!

Hey folks - I come to you out of desperation and confusion.

My car is a 2009 E90 335i. Full bolt on - COBB Stage 2+ OTS tune with 129k miles.

So, the insanity creating rattle came to my attention after installation of VRSF 3" catless downpipes. I am not certain if the rattle was present prior to installation and was simply muffled by the cats or not - but this is when I noticed it. I got in the car after installation and was incredibly excited to hear the throaty sound and give it a couple revs. Sadly, the experience was tainted when a metallic rattle screamed over the exhaust note.

I've been chasing the rattle for a couple of months (however somewhat leisurely) and I am at the end of the road for possible solutions with the exception of one.

I'll layout the symptoms that I have and then follow that up with the troubleshooting adjustments I have made.

Symptoms:
1. The rattle occurs at idle, during acceleration, and during deceleration when the throttle is lifted (it's loudest at this time).
** I was under the impression that wastegate rattle is an issue only during deceleration when throttle is lifted. This is the part that has me most confused since my rattle is constant.

2. The rattle does not seem to be affected by engine operating temps. It occurs at cold start as well as after the car has been driven for miles and miles. For instance, I will hear the rattle when I pull up to a fast food drive-through window even after 30 minutes of driving.
** Again, I was under the impression that most wastegate rattles were a cold engine issue.

3. The rattle is most easily heard when laying / crouched just behind the passenger-side front wheel. From above the engine with the hood closed, it is quite muffled.

4. I don't appear to have a boost leak nor any overboost issues. Everything seems to be operating well based on logs as well as just while driving keeping an eye on the COBB AP3 display for WGDC, Boost, Load, etc.

5. Each time I try a solution - I think I have fixed it. The reason for this is that after literally every troubleshoot the rattle goes away and I get to hear the beautiful drone without a metallic intruder. The car sounds exactly as it should at idle, during revs, and while driving. However, after a trip or two in the car, my heart is broken as that sound rears it's ugly head again.

--------------------------------
Solutions that I've tried:

1. My first solution assumed user error during installation. I installed the downpipes myself in my garage and figured a slight error made the most sense.
So, I first simply tightened the V-Clamps on each. This didn't solve the issue.
I tried tightening the brace that is located just before the rear cats assuming that I may have left this loose. That wasn't the problem.
I tightened the steering rack bolts as well - just in case. That wasn't the issue.
So, I removed them altogether and reinstalled and made sure that they were not touching each other, that no heatshields were rattling, etc.

I can rule out poor installation.

2.My initial attempt focusing on the wastegates was to tighten the rear actuator arm. I bought the stubby 10mm wrench and a set from Sears that included a 4mm wrench.
I marked the current position of the arm with a sharpie and tightened the arm 2 turns until it was tight.
The rattle was gone for a couple of drives and then returned - breaking my heart in the process.
So, reluctantly, I went back and tightened the rod once more thinking that perhaps I didn't get the 10mm nut tightened enough. I went just a half a turn. Rattle was gone for a drive and then returned once again.

3. I read about the issue with the exhaust flap vacuum on these cars. I went back to my trunk to disconnect the wires behind the taillight and found that they were already disconnected by the previous owner. No resolution there.

4. I replaced the vacuum lines with Voracious lines - partly because I thought it would be fun and partly because I thought that maybe the solenoids needed some help and it was a dirt-cheap replacement.

No resolution.

5. I replaced both boost solenoids. Once again, the rattle was gone - this time for about a day's worth of driving - both WOT and regular cruising.
Then, suddenly, a day and a half later, I hopped into the car for a quick errand run and when I pulled back into my garage I heard the rattle again and it has not left since.

------------------------

There is one thing that I have not tried which I've read about on the forums here. The washer solution for the front turbo wastegate. I've been reluctant to do this for a couple reasons - mainly because the metallic sound doesn't seem completely consistent with a wastegate issue based on the symptoms. Not dependent on engine temperature, not occurring only during deceleration, etc. I also thought that I read that the rear wastegate actuator arm is primarily the one that runs into the problem due to the extreme heat cycles it experiences. Also, I haven't done it simply because it's not as convenient to get at.

I'll post a video of the sound tonight - I'm currently at work.

In the meantime, could that front wastegate actually be my culprit? Or, does ANYONE have an alternate idea that I should try? Is the front wastegate becoming a more common issue?

As a reminder since this is a long post, my car is a 2009 E90 335i. Full bolt on - COBB Stage 2+ OTS tune with 129k miles.

I greatly appreciate any help and I apologize for the long post.
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Last edited by WatchWolf34; 12-12-2017 at 05:29 PM.
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      12-12-2017, 02:30 PM   #2
Antetokounmpo
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that my friend is wastegate rattle. stock downpipes were just muffling it.
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      12-12-2017, 02:36 PM   #3
WatchWolf34
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Quote:
Originally Posted by Antetokounmpo View Post
that my friend is wastegate rattle. stock downpipes were just muffling it.
That's bittersweet to hear.

Thinking it's the front then...or just convince the wife that it means the turbos need to be replaced
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      12-12-2017, 04:33 PM   #4
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Any thoughts as to why it seems resolved each time and then resurfaces? Is that common?
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      12-12-2017, 05:14 PM   #5
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Inconsistency may come down to temperature changes. Just throwing that out there.
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