Rear main seal noise!

[Maud]

Gents - I think I have a rear main seal issue. After doing some research here I found this thread and video with similar noises that I am hearing:

http://www.1addicts.com/forums/showthread.php?t=516641

In my case however, the noise only occurs as I am about to come to a complete stop and lasts maybe 2-3 seconds. It only happens when the car is warm.

I am not leaking or seeping oil. This is really just more an annoyance from my end.

Is there any harm in leaving it? Anyone else have this issue? Is it possible I could have another issue?

I have a 2012 135 with approx 35000 miles.

Thanks all!

[Dilmorecg]

Dang, I have been searching to figure out what this issue is...so thanks for the post. I am getting the exact same noise and symptoms in the video and what you describe. Only when the engine is winding down to stop. Its intermittent. I hope this isnt too expensive...I am out of warranty.

[MightyMouseTech]

Rear main seal? Not the front main seal?

[mr.fabulous]

I cannot speak for these newer motors... but in an M52, a clogged oil separator will cause the engine to pull air in around the rear seal and it makes the most erie groan. This happened to an older car of mine at about 50Kmiles. IIRC, you hear it most while decelerating with your foot off the gas (although it's been a few years and I cannot promise I'm remembering that correctly).

[Maud]

Thanks for the insight all. I (luckily / unluckily) have a few weeks left under warranty so I better get this looked at ASAP. I will post the outcome.

[paranoidroid]

I have the same noise.. 2011 135i. Any followup on your issue?

[Jarryd]

Hey guys, i have exactly the same issue. Dealer says its the rear main seal as well. I ll get my car back tmro apparently so i will be able to report back then.

[Dilmorecg]

Mine was definitely the rear main seal. Dealer wanted ~$1300 to replace and my 3rd party warranty wouldn't cover it since it was just a noise and wasn't leaking. From talking to the dealer it sounds like its a fairly common issue. The dealer also told me it wasn't that big of a deal and not an urgent thing to get fixed...not sure how I feel about that.

[mr.fabulous]

Not an emergency... but noise == leak. Rear seal might not be the root cause (in older BMW motors this was caused by a clogged oil separator).

[twinboost_MD]

are the rest of you guys having the same exact issue as the OP? i mean exact as in 2-3 seconds when coming to a stop? the linked video seems pretty consistent unlike the OP's issue. Could just be the tensioner or belts, colder weather causes things to expand and shrink so check it out.

Looks like OPs issue is related to engine speed, or maybe the torque transfer from second to first gear

[Dackelone]

I also believe a bad rear mail seal will also cause another type of noise... namely a fluttering sound when rev's fall from under 3K to 1.5K revs. Its nothing like the sound in that link'd thread.

My car does this, but only after a good hour's drive. Its been doing it for 60K kms and its no big deal to me. I will replace the rear main seal when I have to replace my clutch. (when ever that happens).

Dackel

[Maud]

Sorry for the delay everyone. When I took it to the dealer, they noted three things (straight from service record):

Complaint: Diagnose and report on whistling noise noticed from engine area when car approaches a stop.

Correction: Confirmed customer complaint. removed under panels and tested operation again and found still present. Smoke tested vehicle and found leak at valvetronic servomotor. Removed and replaced gasket. Noise still present. Removed aux fan and tested operation. Found still present. Removed drive belt and found noise still resent. Opened oil cap and tested operation. Found noise no longer present. Checked crankcase pressures and found pressure too low at 6MBAR. Removed and replaced faulty valve cover. Tested crankcase pressures after replacement and confirmed OK at 14.2MBAR. Tested operation and found noise still present however much harder to reproduce. Removed harmonic balancer and inspected front main seal. Found seal faulty. Removed and replaced faulty front main crankshaft seal. Tested operation and confirmed all OK.

Perhaps I had a few other issues that needed to be resolved but the front main crankshaft seal seemed to be one of the main culprits. Car has been fine since!

[mr.fabulous]

They replaced the valve cover? Not the valve cover gasket? Really?

And, yeah, that's the test... pull the oil cap and see if the behavior changes... and if it does, you have a crankcase pressure problem (I should have remembered that, been a long time).

[Maud]

Originally Posted by mr.fabulous

They replaced the valve cover? Not the valve cover gasket? Really?

And, yeah, that's the test... pull the oil cap and see if the behavior changes... and if it does, you have a crankcase pressure problem (I should have remembered that, been a long time).

Sorry - it was the gasket! I missed the word when typing

[Dilmorecg]

You can also test/reproduce this to make sure its the front or rear main seal by removing the oil cap while idling for a few seconds then putting it back on. It should make the squeal once the pressure builds back up. If you listen under the car when doing that you can tell if its the front or rear seal.

Also, Ive read that the N55's don't have PCV's and that it is built into the valve cover so if there is a problem with the crankcase pressure equalizing I think the whole cover needs to be replaced....Not 100% on this one but Ive been researching what might cause this issue to figure out it there is an easier fix.

[RedFive]

Yep. Had this same issue (except front main seal), and just had it fixed after three trips to two dealerships, replacement of front rotors and pads (originally diagnosed as the issue, then finally replaced due to warped rotor), and three SAs and five or so techs telling me they couldn't hear/replicate the issue.

This week I got a tech in the car with me, reproduced the sound in minutes, and finally had someone believe me. I should have come here first.

It should also be noted I was at the dealer because my car had been towed there after the electric cooling pump died, with resultant total loss of power on the highway (at 51,000mi., even). Thankfully I bought it off lease, CPO, and just paid a diagnostic fee, but this seems like a lot of problems with the car already.

[MightyMouseTech]

Originally Posted by Dilmorecg

Also, Ive read that the N55's don't have PCV's and that it is built into the valve cover so if there is a problem with the crankcase pressure equalizing I think the whole cover needs to be replaced....Not 100% on this one but Ive been researching what might cause this issue to figure out it there is an easier fix.

N55 do not really have a throttle body, so only way for the engine to produce vacuum is with a separate vacuum pump. There are two pumps in the valve train and two vacuum chambers in the valve cover. One is for things like wastegate control etc, the other pump is for brake power assist. It also runs the engine at a vacuum for blowby gas accumulation, what is normally part of a PCV system. So a faulty seal will actually allow air INTO the engine, which will make a kind of farting noise.