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2011 335i N55 accessory squeal troubleshooting - stumped

923 Views 7 Replies 4 Participants Last post by  Doug Huffman
Hi everyone,

I have a squealing noise coming from the front accessory area of my 2011 E92 335i coupe with an N55. It all started after I picked up my car from getting a valve cover gasket and oil filter housing gasket done at a BMW dealership. I assume the dealership cleaned up the oil in the bay with some degreaser. When I picked the car up I could hear it very subtly and thought it would go away in a couple miles if some water rusted a bearing a little bit. Sure enough it did. This was a long time ago and it has been getting worse at startup ever since. The noise goes away ENTIRELY when the engine builds the smallest of temperature (<5 minutes driving easy). I should also mentioned that it is FAR more quiet and goes away within a minute during hot summer months even before replacing all the belt items.

Items repaired and fixed so far about 30 days ago

1) New continental belt (old one still looked perfect after inspection)
2) Automatic Belt Tensioner Assembly and both drive belt idlers
3) Dealer installed valve cover gasket (January 2019 when I first notice the noise at startup)
4) PCV valve changed 2017 as preventative medicine. I've heard those videos and this sound is nothing like that.

Just curious if something similar has happened to someone else before I start tearing anything apart. Wondering if it is alternator related or the AC condenser clutch mechanism.

Any help or advice would be great. Next chance I get I can post a soundclip if anyone is curious.
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Also, with all the COVID-19 I have been working at home and barely putting miles per week on the car. Plus I live in Wisconsin, so it's getting colder now too. If that makes a difference...
Verify it's something on the accessory drive, take the belt off and start the car, if it is on the accessory you should be able to sling each pulley and hear which one makes the most noise. Does cycling the ac pump make it change/stop?

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Hi everyone,

I have a squealing noise coming from the front accessory area of my 2011 E92 335i coupe with an N55. It all started after I picked up my car from getting a valve cover gasket and oil filter housing gasket done at a BMW dealership. I assume the dealership cleaned up the oil in the bay with some degreaser. When I picked the car up I could hear it very subtly and thought it would go away in a couple miles if some water rusted a bearing a little bit. Sure enough it did. This was a long time ago and it has been getting worse at startup ever since. The noise goes away ENTIRELY when the engine builds the smallest of temperature (
Items repaired and fixed so far about 30 days ago

1) New continental belt (old one still looked perfect after inspection)
2) Automatic Belt Tensioner Assembly and both drive belt idlers
3) Dealer installed valve cover gasket (January 2019 when I first notice the noise at startup)
4) PCV valve changed 2017 as preventative medicine. I've heard those videos and this sound is nothing like that.

Just curious if something similar has happened to someone else before I start tearing anything apart. Wondering if it is alternator related or the AC condenser clutch mechanism.

Any help or advice would be great. Next chance I get I can post a soundclip if anyone is curious.
That sounds like a leaking oil filter housing gasket .
Trouble shooting so far:

1) Open oil filler cap to check if crank case pressure is causing a seal to squeal - Negative
2) Water on the belt - Positive result. The noise instantly went away.

A reminder, the belt and aforementioned pulleys are all brand new. The belt is the suggested Continental part# on FCP Euro. The sound did not change after swapping those parts in.

The only thing I can think of is a pulley misalignment. If that's true it's going to be hard to track down which item is bad because the belt is running really true on all the surfaces. This ChrisFix (min 2:00-3:00) video is almost identical to what I'm experiencing.


Has anyone encountered this and can give a good guess which item is likely worn out (alternator, power steering, A/C condenser)?

I was also thinking of thinking of trying belt dressing or aerospace 303 protectant for a simple long lasting fix.
Also, the audible squeaking is coming from the alternator area.
Thinking about trying this first too before going down a rabbit hole looking for "bad" components since it's so easy and cheap. This looks a little more sophisticated than gimmick sticky belt dressings.

Inspect the elastomer ‘rubber’ element of your vibration reducer. If it has split the two halves may be spinning against each other.

The ONLY liquid in your engine compartment that is not harmful to rubber is pure water like rain water or DEF. EVERY other liquid - oil, PS, ATF, antifreeze, brake fluid - is deleterious.
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