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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N55 Turbo Engine / Drivetrain / Exhaust Modifications > Intermittent N55 chirping sound under heavy braking.. PCV valve or something else?
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      04-01-2022, 11:40 PM   #1
Aaroona
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Intermittent N55 chirping sound under heavy braking.. PCV valve or something else?

I am having trouble with my vehicle at the moment, whereby when I am braking hard from speed, or facing down a hill while braking (even at low speed), I hear a sound that sounds very similar to the PCV valve issue that is already documented for the N55.

I am however not able to replicate the issue any other way - it does not occur under any normal acceleration/deceleration, any engine revving, at idle, which is the conditions which everyone else seems to have.

Is this the PCV valve still? Or is it the front crank seal? or is this possibly something else?

I had my local workshop do a smoke test on the system and they said there were no leaks... but the sound is starting to really annoy me. Its quite loud, and can definitely hear it when the window is down.
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      04-02-2022, 09:35 AM   #2
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Likely what it is yes
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      04-02-2022, 05:07 PM   #3
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Unless its actually something to due with the brakes/suspension/etc. Did you confirm its coming from underhood?
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      04-03-2022, 02:00 AM   #4
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Quote:
Originally Posted by thejeremyman9 View Post
Unless its actually something to due with the brakes/suspension/etc. Did you confirm its coming from underhood?
I'm fairly sure it is (it does sound exactly like the chirping/dolphin like sound described in relation to PCV)- I don't know how to confirm it, since it only happens while driving and braking. Any ideas how I may do that?

I managed to at least confirm the noise wasn't present while the car was cold this morning, but managed to make a noise once the car was hot.
It happened when in drive and neutral. Also occurred while in comfort and in eco (another post suggested it was worth trying)

Since it happens only when heavy braking or down hill, braking and warm, whether its the main rear seal? Oil moving to the front of the engine, leaving the rear seal "exposed" and allowing air past?
Or am I talking crap and that's not how it works?

I had an oil leak fixed recently, and noticed my oil was getting low, which seemed strange to me. But found the oil filter housing gasket needed replacing (and was leaking) so attributed it to that.


Quote:
Originally Posted by n55david View Post
Likely what it is yes
Any way to really confirm which part it is exactly before replacing anything? The smoke test came up negative.
I'm going to call the workshop tomorrow to ask some more questions, but an a bit at a loss... Don't want to start throwing money at parts until I am somewhat sure.
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      04-03-2022, 01:50 PM   #5
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Quote:
Originally Posted by Aaroona View Post
I'm fairly sure it is (it does sound exactly like the chirping/dolphin like sound described in relation to PCV)- I don't know how to confirm it, since it only happens while driving and braking. Any ideas how I may do that?

I managed to at least confirm the noise wasn't present while the car was cold this morning, but managed to make a noise once the car was hot.
It happened when in drive and neutral. Also occurred while in comfort and in eco (another post suggested it was worth trying)

Since it happens only when heavy braking or down hill, braking and warm, whether its the main rear seal? Oil moving to the front of the engine, leaving the rear seal "exposed" and allowing air past?
Or am I talking crap and that's not how it works?

I had an oil leak fixed recently, and noticed my oil was getting low, which seemed strange to me. But found the oil filter housing gasket needed replacing (and was leaking) so attributed it to that.



Any way to really confirm which part it is exactly before replacing anything? The smoke test came up negative.
I'm going to call the workshop tomorrow to ask some more questions, but an a bit at a loss... Don't want to start throwing money at parts until I am somewhat sure.
Can you put a gopro underhood or somewhere and record?
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      04-04-2022, 05:58 PM   #6
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Quote:
Originally Posted by thejeremyman9 View Post
Can you put a gopro underhood or somewhere and record?
Unfortunately not, as I don't own one (or any other action-type camera for that matter)
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      04-17-2022, 04:56 AM   #7
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Just bumping to get it seem, in case anyone else has more ideas before I hand it over to a mechanic... I'm beginning to feel like it's time to move this vehicle on, seems to be more issues popping up with it now at around 70k miles/112000km.
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      04-18-2022, 04:56 PM   #8
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To my "simple"mind. If it only is occuring during a braking event (if I read all correctly), it would appear to be brake or suspension related. Does this EVER occur during a non-braking event?
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      04-18-2022, 05:40 PM   #9
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Quote:
Originally Posted by Orion4 View Post
To my "simple"mind. If it only is occuring during a braking event (if I read all correctly), it would appear to be brake or suspension related. Does this EVER occur during a non-braking event?
Not at this stage, only seems to occur during braking.
I had the same thought as you, but the sound it makes, is like in this video, though mine is more pronounced


but then someone else from another post mentioned that they had the same issue and it was the belt tensioner.

So really the options I have at the moment are;
- PCV valve cap
- Front crank seal
- Rear crank seal
- Belt tensioner

Last edited by Aaroona; 04-18-2022 at 05:51 PM..
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      04-18-2022, 05:58 PM   #10
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Quote:
Originally Posted by Aaroona View Post
Not at this stage, only seems to occur during braking.
I had the same thought as you, but the sound it makes, is like in this video, though mine is more pronounced

but then someone else from another post mentioned that they had the same issue and it was the belt tensioner.

So really the options I have at the moment are;
- PCV valve cap
- Front crank seal
- Rear crank seal
- Belt tensioner
I dont see how it could be tensioner given the circumstances under which it occurs, but if you are over 60k miles and they are original from 2012 it could be worth doing tensioner and belt as preventative.

Not sure about the seals given the circumstances and no oil leaks
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      09-19-2022, 04:33 AM   #11
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Quote:
Originally Posted by thejeremyman9 View Post
I dont see how it could be tensioner given the circumstances under which it occurs, but if you are over 60k miles and they are original from 2012 it could be worth doing tensioner and belt as preventative.

Not sure about the seals given the circumstances and no oil leaks

So I had it checked by a BMW specialist workshop today, since my generic euro mechanic couldn't help... and... they couldn't help either.
Couldn't replicate the issue, and couldn't confirm what was at fault.



They mentioned a potential small leak at the rear crank seal... could this be my problem?
The testing of the PCV didn't result in any confirmed issue there... its not sucking air, and no issues with smoke or boost test.

Running low on options... the workshop just said to live with it and nothing to worry about!?
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