[vespa]

Suddenly my engine started making a loud chirp chirp chirp noise when I apply the brakes at low speeds. It sounds kinda like an old Chevy van with bad power steering and I'm hoping someone has heard this before and can direct me to the source. It's an odd one and very difficult to track because it stops shortly after the car stops.

It seems to occur when:
- Car is stopping or recently stopped. Once I was able to open the hood and look/listen to the last few chirps but usually it stops within a couple seconds of stopping the car.
- Brakes are used. Even the parking brake causes it so it seems unrelated to vacuum boost. Coasting to a stop by going uphill simply slowing with engine braking does not trigger it. Downhill stops with firm braking are most aggravating. I can even make it chirp louder or softer by varying brake pressure.
- Engine has just revved. It need not be in gear but it does need to have revved just prior to stopping. So for example I can coast downhill in neutral, tap the gas, then pull the handbrake and it will begin chirping.

It seems too slow to be the radiator fan and occurs independently of the A/C or steering. Could it be a squeaky diverter valve? But why would the valve be moving around so much when the engine is idling smoothly in park? The one time I got the hood open it just sounded like it was coming from the middle of the engine bay somewhere. Happens hot or cold, but only a few times per week so it's very difficult to reproduce consistently.

Update: Cause was found to be crankcase pressure regulating diaphragm integrated within the valve cover. See here for details: http://www.e90post.com/forums/showthread.php?t=1197666

Attached videos say it all. Remove the .pdf extension. The driving video illustrates the front main seal chirping like a dolphin whenever I hit the brakes. The under-hood video shows the crankcase vacuum reaching -1.5psi (-105 mbar) as the rear main seal squeals and silences in response to the oil cap being opened.

[vespa]

OK, I realized I'm a turbo noob. Apparently this is classic diverter valve flutter and there are a hundred Youtube videos documenting (sometimes praising) the same phenomena. So now what could have caused this to suddenly happen on a stock engine? Some vacuum hose leak or something? I'm also hearing a lot more wheezing and whistling from the turbo lately, maybe related?

[vespa]

Problem solved. Turned out to be the front main crankshaft seal just like Sara posted in this thread:
http://www.e90post.com/forums/showthread.php?t=629612

[SUPAN]

Do you have a picture or a part number?

I have changed my crank shaft pulley and the sound is gone for months and this reappears...

[vespa]

There's nothing interesting to see with the shaft seal. The only wear/damage it had was that the outer dirt-lip was mostly torn off. This might have been torn during removal or maybe it fell off on its own and got sucked into the seal to cause the failure? Anyway it was interesting that they used a dremel to cut thru the seal's steel support ring. I don't know how/why they cut it but it looks to be cut from the outside-inward somehow. Hopefully I don't have a big cut in my crankshaft now.

An anerobic sealant is used for reassembly and part numbers with prices from Husker are below.

11118618864 Shaft seal $22.16
83197515683 Loctite primer 4ml $9.24
83197536051 Loctite sealant $51.59

[SUPAN]

Originally Posted by vespa

There's nothing interesting to see with the shaft seal. The only wear/damage it had was that the outer dirt-lip was mostly torn off. This might have been torn during removal or maybe it fell off on its own and got sucked into the seal to cause the failure? Anyway it was interesting that they used a dremel to cut thru the seal's steel support ring. I don't know how/why they cut it but it looks to be cut from the outside-inward somehow. Hopefully I don't have a big cut in my crankshaft now.

An anerobic sealant is used for reassembly and part numbers with prices from Husker are below.

11118618864 Shaft seal $22.16
83197515683 Loctite primer 4ml $9.24
83197536051 Loctite sealant $51.59

Thanks... not too sure if i need the entire crank shaft pulley again or just the seal will do...

lets see... if i can save 800 bucks...

many thanks....

[Texas2904]

Wow that 36 page thread with Sara was painful to read. Where are all those guys "just there to help" when you need them?

My car has been doing this as well. 2011 n55 sedan.

Just to confirm, you replaced the front seal and that was it? Did the dealer identify the problem or did you have to tell them?

[vespa]

Just the seal was replaced, nothing else. I had no idea what it was and googling "funny noises from my engine" didn't exactly help. The dealer didn't know at first either -- I provided them with the video and plenty of description yet they spent several days diagnosing it. Finally they traced it down to crankcase ventilation and were able to eliminate it by pulling the PCV hose which then led them to examine the crank seal. After all that, they found a TSIB on it but did not provide me with the number.

BMW has used this same part number (11117547842) on every engine since the beginning of time but sometime between Sara's 2012 repair and mine, they updated the part to 11118618864. Maybe the N55 uses more crankcase vacuum than other engines and the old one-size-fits-all seal just can't handle it?

[Texas2904]

Thanks. Taking my car in Monday and the warranty expires on the 3rd. I've complained about the issue in the past and they haven't been able to diagnose. I'm hoping they can just trust me on this one.

[Luckystrike24]

Vespa,

The N55 does have more crank case vacuum than the N54.

N54 335i - 17 mbar
N54T 335is - 14 mbar
N55 - 38mbar

[Texas2904]

Just to add to this thread, I took my car in and gave my tech your video and a link to this thread. They weren't able to diagnose the problem otherwise, so they went ahead and replaced the front seal without too much pushback. Noise is gone!

[JETmn]

My car makes this noise any time at idle now. Did anyone else's do this continuously? I was thinking it was a bad belt/pulley but this has me thinking otherwise now.

[vespa]

Jet, if the noise continues after you loosen the oil cap then you apparently have some other problem. Note that this will cause a CEL.

[JETmn]

I will give it a shot, thanks!

[vespa]

Update: 3 months after replacing the front main seal, the rear main blew, sounding exactly like this:



It turns out that the seals aren't actually "blowing", they're just sucking -- literally sucking in air and whistling like a party balloon. In my case this was the result of a failed PCV valve allowing excess crankcase vacuum. I replaced the PCV valve, not the rear main seal, and all is well now.

Detailed PCV valve info here: http://www.e90post.com/forums/showthread.php?p=18947012

[weehe126]

watched the video, nearly had a heart attack. My car is making the same sound in the front. Saw you said its the pvc valve and got happy as that should be easy. Remembered the valve is integrated into the VC and they are $400, now i'm sad again lol.

But I have to say thank you very much for this post. I actually bought a whole accessory belt kit thinking it was that. Now I'll get a new VC.

[vespa]

Just be sure to do the simple oil cap and smoke tests first before diving into the valve cover.

[weehe126]

Originally Posted by vespa

Just be sure to do the simple oil cap and smoke tests first before diving into the valve cover.

Yup, significant vacuum when I took the cap off and the squealing stopped when off, then started right away when put back on.

[vespa]

The oil cap test absolutely confirms that the noise is coming from a main seal but it doesn't explain why. It's certainly possible that the seal is bad and the PCV system is fine.

The smoke test will absolutely confirm a bad PCV valve and is very simple to do. Lift off the decorative center engine cover and unclip the little decorative cover from the hose barb. Hold a burnt match or something very close to it and if smoke is continuously drawn in, the valve is unquestionably broken.

If the smoke test is inconclusive, the next step would be to replace the oil cap with one that can measure pressure, then confirm that idle pressure is around -0.55psi, particularly while the noise is present. If you're reading -1.0psi (or -1.5psi in my case), the PCV valve is absolutely broken. Otherwise, you just have a bad main seal. Front tends to make a chirping or squeaking sound, especially when hitting the brakes while the rear tends to be a louder more continuous squeal.

I added an oil cap/pressure test/rear main seal video to the first post.

[weehe126]

Originally Posted by vespa

The oil cap test absolutely confirms that the noise is coming from a main seal but it doesn't explain why. It's certainly possible that the seal is bad and the PCV system is fine.

The smoke test will absolutely confirm a bad PCV valve and is very simple to do. Lift off the decorative center engine cover and unclip the little decorative cover from the hose barb. Hold a burnt match or something very close to it and if smoke is continuously drawn in, the valve is unquestionably broken.

If the smoke test is inconclusive, the next step would be to replace the oil cap with one that can measure pressure, then confirm that idle pressure is around -0.55psi, particularly while the noise is present. If you're reading -1.0psi (or -1.5psi in my case), the PCV valve is absolutely broken. Otherwise, you just have a bad main seal. Front tends to make a chirping or squeaking sound, especially when hitting the brakes while the rear tends to be a louder more continuous squeal.

I added an oil cap/pressure test/rear main seal video to the first post.

If you are talking about the small vac nipple on top right next to the high voltage warning, then yes mine is pulling in the smoke.

[vespa]

That's the one. Limit your driving until the valve cover is replaced and hopefully your main seals won't get too worn.

I would sure love to see if yours failed in the same way. I cut mine open with a vibrating saw: cut low around the base, not too far in, and don't pull on the rubber diaphragm -- it's bonded to the cap. The radial crack in my diaphragm is perplexing and I think it must have been caused by an improper boost leak test by the previous owner -- any idea what might have caused your trouble?

[weehe126]

Unfortunately the noise popped up a day before a 2000 mile road trip lol. I thought it was the acc belt/tensioner so I took the trip. Probably have put 2500 miles on it now since it started. Weird thing is, the sound is less often now, very inconsistent. I plan to cut open my VC and take a look. There was nothing out of the ordinary for me, just noticed the sound coming home from work and hadn't touched the engine in weeks. Ordered a new VC last night so hopefully will be here before thanksgiving.

One thing I did notice is that I consumed over a quart of oil on the trip. Before I had never consumed any oil between oil changes. Also my exhaust gas smells of oil so am pretty sure i'm pulling a lot back through the intake track and valves. Plan on doing a walnut blast so will see how bad they look.