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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > Engine Knocking Noise After Cold Start - Vacuum Pump?



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      12-15-2016, 08:40 AM   #1
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Lightbulb Engine Knocking Noise After Cold Start - Vacuum Pump?

Been hearing this metallic knock for a long time, never got around doing anything about it. It's still the same, which is kinda weird. It happens only when the engine is cold. It is very noticeable at the end of the video.

I have done some brief research and some say it is the vacuum pump. Has this happened to anyone on here? The car will be going to the dealership soon anyways, I want to enquire about this and the Vanos recall, so I just wanted to get some info from you before I go there.

Thanks.

My video:


535i:
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      12-15-2016, 10:46 AM   #2
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Definitely not a common problem if that is it. It does sound like the video you linked to. Most of the noise is just cold injectors, but I can hear what you are talking about too.
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      12-15-2016, 01:33 PM   #3
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Definitely not a common problem if that is it. It does sound like the video you linked to. Most of the noise is just cold injectors, but I can hear what you are talking about too.
Yeah.

Since the vacuum pump operates other auxiliary components such as the wastegate and exhaust flap, I wonder if the golf-tee mod could have any influence.
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      12-16-2016, 05:15 PM   #4
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I guess no one has had this issue on here.

Hopefully will know more in the following week.
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      12-20-2016, 04:15 AM   #5
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under intake manifold runner#1 the cloesest to front bumper, there is a vacuum pipe it could be loose and not fitted properly.
I had that problem when i removed my intake manifold and back. just a loose pipe i hope.

edit: not sure if Eseries are same as Fseries
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      03-16-2018, 02:31 AM   #6
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same problem

hi, i have the same noise like you, but it lasts all the time during engine is running..

did you find out the exact reason fort this noise?

please let me know..
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      03-19-2018, 07:51 PM   #7
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Same noise, seems many n55 owners have this noise on cold start. I hope we can finally get an answer
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      03-20-2018, 07:33 PM   #8
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Got that same noise too :/
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      03-20-2018, 07:45 PM   #9
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Quote:
Originally Posted by jagstang.t View Post
hi, i have the same noise like you, but it lasts all the time during engine is running..

did you find out the exact reason fort this noise?

please let me know..
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Originally Posted by northbranchroad View Post
Same noise, seems many n55 owners have this noise on cold start. I hope we can finally get an answer
Quote:
Originally Posted by Hannibal4444 View Post
Got that same noise too :/
Have not driven the car for a few months, but afaik, it has not gotten any worse at all since I made the video.
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      03-20-2018, 08:24 PM   #10
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Also have this noise. Super noticable on cold starts but once it's fully warmed up it's gone
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      03-21-2018, 06:24 AM   #11
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i noticed this noise on mine a while ago... not had any problems but now u got me worried
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      03-28-2018, 07:24 AM   #12
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Mine does it too. I'm guessing this is generally accepted as normal?
I have very little knowledge of German so i couldn't translate the youtube discussion. What was the fix? New vacuum pump?
But all vacuum operated accessories are working fine and brakes are good?
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      03-28-2018, 06:30 PM   #13
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Add mine to the list as well. Same noise I discussed in another thread where it was generally considered normal. Goes away after warmed up. Still wish someone smarter than me would figure it out. The only intel I have so far is that it gets louder when you crack open the oil filler cap while running, so it would appear to be internal. Sorry, I know that's not much of a clue.
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      03-28-2018, 07:01 PM   #14
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Rod knock? We have had a couple N55 people lately with issues
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      03-28-2018, 09:34 PM   #15
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Quote:
Originally Posted by IllSic_Design View Post
Rod knock? We have had a couple N55 people lately with issues
Sounds like one slightly but its not. I have put like 10k on mine since I noticed the noise on my car, may have been there even earlier. Im sure you can't get that many miles with a rod knock.
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      04-03-2018, 07:31 PM   #16
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Mine does the same thing...normal.
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      04-08-2018, 02:23 AM   #17
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Mine does it too...

and so did my 325 e46! I never figured it out on the E46. I swapped Belt idler pulley, tensioner and alternator thinking it was a bearing somewhere starting to go.

Never fixed my issue so when I got My 335 and I heard that same noise I just figured this is normal for BMW lol
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      04-09-2018, 09:41 AM   #18
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The sound def seems to come from the direction of the intake vanos during cold start. Did someone take it to the dealer and wonder what BMW has to say about this.
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      04-10-2018, 12:54 AM   #19
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thank you everyone for contributing to this thread. i too have the noise at startup and it's scary af knowing that people's n55's rod bearings are going. at least i'm not alone. i'm on 91 ca gas, have ppk, and at 62k miles.
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      04-10-2018, 09:48 AM   #20
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Quote:
Originally Posted by dleccord View Post
thank you everyone for contributing to this thread. i too have the noise at startup and it's scary af knowing that people's n55's rod bearings are going. at least i'm not alone. i'm on 91 ca gas, have ppk, and at 62k miles.
This has nothing to do with rod bearings and NO peoples rod bearings are not going. It all assumptions not a single hard evidence. So people stop panicking
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      04-11-2018, 09:00 AM   #21
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This same noise noise is present with my car as well and it's only present on cold starts and goes away once the car warms up. The knocking noise does not speed up or change as the engine revs, so I'm not particularly worried about it being a bad rod bearing or anything of that sort. The car still performs just fine too.

I had an indy shop recently replace the harmonic balancer in my car and they were listening closely to the motor on cold starts because I mentioned a squeaking noise that was only present during such starts. They didn't raise any concerns, so I'd guess that it's fairly normal or at least not anything to worry about.

That said, I'm judging that based only on the video, so if you're really worried about it you should probably still get it looked at. I'd be curious to know what another shop/mechanic would have to say about it.
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      04-24-2018, 05:05 PM   #22
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Sometimes I hear tiny knocking noise during cold start. I have the car for a year since it was at ~86k miles. Performed regular maintenance and check for codes from time to time - all clean. Just like everyone says, it goes away after slight warm-up, everything's smooth.
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