[cschiavoni]

2011 328xi, 75k miles

Recently had spark plugs, ignition coils, and engine belt replaced. Oil change about 500 or so miles ago. A few days ago my check engine light came on, and I heard a little screeching sound coming from the engine. Immediately drove to my mechanic, he said coolant looked low and topped it off. I did not get a coolant low warning at any point. Anyways, engine light went off but soon back on. Then off. Then on again. Screeching intensified and has over the last two days. It is fine upon start up, after driving for a little bit it will start screeching LOUDLY and when I say loud I mean very, very loud. Nothing ever pops up on dash, only thing there is engine light. Had codes read at AutoZone and got a P0012 and not sure how this could be related to that code (camshaft position - timing over retarded). The screeching noise stops when I'm acceralating hard and has slowly gone from only happening here and there when the car starts to slow down to happening constantly after acceralating even after idle. I tried to get a video but once I turn the car off the sound goes away and doesn't come back until I drive it a bit. Revving engine doesn't recreate noise.

Tonight was the last straw however, it started screaming louder than normal (but how) and the engine had a VERY rough idle, as in physically noticeable. Thankfully I was a block from my house, parked it and will not be touching it until tomorrow in the morning when I'm going to attempt to get it to my mechanic who is about two miles away.

Nothing came on during the rough idling btw, just that old yellow service engine soon light.

I know I'll know more tomorrow but wanted some insight. I've searched the forums and seen others have gone through similar issues but haven't found one quite like mine.

Halp.

PS. If this is in the wrong forum, please move it, I'm still new sorry.

Edit: Found new mechanic, read to bottom.

[Efthreeoh]

Sounds like to me you have two issues going on. 1) I have the mechanic clean and swap the VANOS solenoids. You can look in the DIY section on E90 post for more information about that. 2) The screeching issue sounds like the drive belt has a problem related to a worn out pulley or one of the drive accessories is requiring more torque to turn than normal and the belt is slipping. I'd have your mechanic replace the drive belt, the drive belt tensioner, and the idler pulleys.

Is your mechanic a trained BMW Tech? From what you described he did when you came in with a noise problem and check engine light, sending you away with topped off coolant was not the correct answer. Are you sure he knows what he is doing?

[STR8-6IX]

the low coolant warning will only com on when you are much too low on coolant, like 3L low. the coolant will be on the low mark inside the reservoir with only 1L gone so its good he topped it up. whats not good is that he clearly did not solve the problem. take your car to a different mechanic.

[patents]

If my mechanic told me being a little low on coolant caused a loud screeching noise I would never ever go back to him.

As stated, it's something related to the accessory belt. Either the belt itself or something attached to it. Probably more than just the belt since you are having idle problems. Something is bogging the engine down.

[cschiavoni]

When he topped off the coolant he was closing up and didn't have any time to really look at it. That said I went this morning and he said it looks like the secondary air pump is the problem. I'm on my way to another mechanic right now (a BMW tech recommended on this forum) trying to get a second opinion. I really love my mechanic, he's a decent guy and always been great to me but I have been doubting his ability lately and this solidified that doubt.

[cschiavoni]

VANOS solenoids look to be the culprit. Think I found my new mechanic as well.

[Efthreeoh]

There is a vacuum pump on the N52. Valvetronic does not create enough manifold vacuum. The N51 has an air pump, which is electric, but the N52 doesn't.

[cschiavoni]

Update: VANOS replacement didn't fix it.. On right track but not there yet. The mystery continues. Left my car at shop and went home. Keep me in your thoughts.

[cschiavoni]

Originally Posted by Efthreeoh

There is a vacuum pump on the N52. Valvetronic does not create enough manifold vacuum. The N51 has an air pump, which is electric, but the N52 doesn't.

Either way he didn't know what he was talking about.

[drawz]

This is a belt/tensioner/pulley/idler/belt-driven accessory type of problem until proven otherwise. Get it fixed before the belt shreds and gets sucked into the engine causing major problems. I had this happen on my n54 5er. Close inspection showed sparks coming from the AC compressor, which turned out to be the problem. But it could be anything along the belt and the pulleys and tensioner are common ones. Replace all at once while you're in there, including a new belt.

I'm guessing the rough idle and check engine light are unrelated to the noise. VANOS solenoids are a good place to start there.

[cschiavoni]

Not a belt problem, CCV system. Needs new bivalve cover.

That's my sad update for today.

[E91 M Sport]

Originally Posted by cschiavoni

Not a belt problem, CCV system. Needs new bivalve cover.

That's my sad update for today.

So my ride made a similar noise twice now. I first thought it was the belt tensioner/pulley so I replaced those and then on my way into work this morning it starts that terrible noise again. I gave it some gas and it went away until the revs dropped down. I shut the car off and what struck me as odd was that the sound progressively went away and not suddenly which is what I had expected.

So what is this bivalve cover you're referring to?