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      02-11-2020, 04:51 PM   #1
Marq_z
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F30 N55 knocking Noise!!

Hi All,

As most of us know, our cars are prone to making all sorts of noises that can trigger our ocd. No one wants to think that something's potentially wrong with their car! After looking all over the internet searching for someone with my same issue, I've decided to just ask bc I cant find an example that's similar to the noise I'm hearing coming from my engine bay! I would greatly appreciate any insight and or validation that my N55 isn't a goner...

Here's the break down:

I bought my 2012 335i sportline about 3 months ago with 73,000 miles on it. After the initial excitement started to ware off a bit I started to notice a KNOCKING SOUND coming from the engine bay that can be heard from inside. Initially I didnt pay much attention to it since the car has been running smoothly without issues, aside from a drivetrain malfunction I experienced, which was resolved with new plugs as the original ones were going. I've since been looking into the noise, but the more I research the more I freak out about potential problems like looking up the symptoms for a cold on WebMd and realizing you have 2 weeks to live. The noise is not there at all on cold start. It's only present once I've driven for awhile and the engine is at operating temperature and at idle. Once I start moving it goes away. It's NOT the injectors as they make a different clicking noise. Has anyone had this same noise coming from their engine bay and is it normal or is there something else going on? HELP!

Possible reasons for the knock:
-vacuum pump
-hpfp
-failing valve cover
- loose hose somewhere?
- loose spark plugs (replaced plugs 2k ago and noticed they were in very bad shape. There's also a lot of carbon build up on the plugs and on the area in the chamber where the plugs sit. They also seemed to look a bit wet with gas?)
- rod knock?

Any insight would be greatly appreciated!
Thanks.

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      02-11-2020, 09:39 PM   #2
T_H_O_M_A_S
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have you tried without running the engine cover ? maybe it rattles on its mounts ?
always difficult to point out the culprit in such a thread
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      02-11-2020, 09:44 PM   #3
thejeremyman9
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You didnt rev the car up at all so we have no way of knowing how this noise varies with RPM, if at all. That is a key test.

You can try to get a mechanic's stethescope and touch it on various parts of the engine to see if you can pinpoint where it is coming from.
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      02-12-2020, 12:41 PM   #4
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Quote:
Originally Posted by thejeremyman9 View Post
You didnt rev the car up at all so we have no way of knowing how this noise varies with RPM, if at all. That is a key test.

You can try to get a mechanic's stethescope and touch it on various parts of the engine to see if you can pinpoint where it is coming from.
I'll try to do that this weekend and will try to locate the source. I just hope it's nothing major..
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      02-12-2020, 12:42 PM   #5
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Quote:
Originally Posted by T_H_O_M_A_S View Post
have you tried without running the engine cover ? maybe it rattles on its mounts ?
always difficult to point out the culprit in such a thread

I hadn't really considered the engine mounts but I'll look into it this weekend. The noise is still there with the cover off.
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      02-15-2020, 09:05 PM   #6
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Quote:
Originally Posted by thejeremyman9 View Post
You didnt rev the car up at all so we have no way of knowing how this noise varies with RPM, if at all. That is a key test.

You can try to get a mechanic's stethescope and touch it on various parts of the engine to see if you can pinpoint where it is coming from.
Here is another video I took today. Still cant seem to figure this out. I's frustrating that it only happens when the car is hot.

https://youtu.be/w3934PA4gt4
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      02-15-2020, 09:06 PM   #7
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Quote:
Originally Posted by Marq_z View Post
Here is another video I took today. Still cant seem to figure this out. I's frustrating that it only happens when the car is hot.

https://youtu.be/w3934PA4gt4

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      02-18-2020, 11:44 AM   #8
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Sounds like a rod bearing. I would not drive it until all of them are replaced.
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      02-19-2020, 11:49 PM   #9
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Yeah. It does sound like a bottom end issue. I have not worked on these cars much, but you could disconnect coil packs one at a time while the car is running and see if the noise gets quiet or quits on any particular cylinder. That's how we used to identify missing and or rod knock issues when I was working on cars years ago.
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      Yesterday, 02:52 AM   #10
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Quote:
Originally Posted by obeeone View Post
Yeah. It does sound like a bottom end issue. I have not worked on these cars much, but you could disconnect coil packs one at a time while the car is running and see if the noise gets quiet or quits on any particular cylinder. That's how we used to identify missing and or rod knock issues when I was working on cars years ago.
I actually did that this past weekend. I unplugged coils one at a time and the thump/knock was still there after the initial hesitation from the engine which gives me some hope that its not a problem in a cylinder. I also listened for it under the car around the oil pan but nothing. The places where the sound was most pronounced were by the turbo/exhaust manifold and the throttle body/intake manifold. I also found this post about a pcv valve failure with the same sound that I have.
https://bmw.***********.com/threads/...ay-sound.3008/

Anyway, I'm taking it in to an indy shop this Saturday. We'll see if they can find the source. Fingers crossed.
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