[Radioactive]

After driving about 60 miles at highway speeds of 70-80mph, I made a stop of about 20 mins. Started the car and a LOUD screeching was coming from engine bay. Popped the hood, but couldn't really identify a source. Belt maybe? But, it didn't sound like the old power steering belt slipping. Restarted the car and it stopped, but started up again on the highway. Luckily I was close to BMW dealer. Stopped in. They could hear the full concert as I drove up. After some arm twisting, of course they wanted to put it in intensive care right away, a tech came out to look at it. Nothing...Made an appointment, drove home 20 miles and nothing. Did a ODB2 scan this morning and no codes. Drives fine.

Anybody experience something similar?

[BOSSBMW]

was the engine running rough at all? any symptoms other than those audible?

[Radioactive]

Nope, only auricular.

[96_Impreza]

http://x3.xbimmers.com/forums/showth...t=belt+bearing
See Post #4.

"2011 X3 35i now at 62K miles had the leaking oil filter housing replaced under warranty at 44K miles. Took a week to get the part.
A week later the belt tensioner pulley bearing failed, loud screeching noise. Tech said that oil leaking from the oil filter housing compromised the lubricant in the pulley bearing and caused the failure.
All repaired under warranty, no charge."

[poiuytre111]

Yes it is probably a seized pulley. I understand that a lot of belt failures start with a pulley failing so you might want to think about changing the belt as well as all/any associated pulleys once it is apart.

[Radioactive]

Thanks for your suggestions. I too had thought about the idler pulley bearings, but my experience with bearings in general, is that once bad always bad. I've driven the car approx. 40 miles since with no problems. As per the experience with the oil leak causing problems, I just had the dealer change the oil about two months ago at which time they went over it and found no leaks. I canceled today's appointment and I'm going to venture a little further from home today.

[Barbera335]

Originally Posted by Radioactive

Thanks for your suggestions. I too had thought about the idler pulley bearings, but my experience with bearings in general, is that once bad always bad. I've driven the car approx. 40 miles since with no problems. As per the experience with the oil leak causing problems, I just had the dealer change the oil about two months ago at which time they went over it and found no leaks. I canceled today's appointment and I'm going to venture a little further from home today.

There is a crankcase oil separator built into the valve cover. These have been known to fail on the N52 and cause the noise you have described. Basically they create excess vacuum in the crankcase which causes air to be sucked past the front main seal. As a test, next time your car is making the noise. With the engine running open the hood and remove the oil fill cap. If the noise goes away it is definitely the oil separator. Unfortunately, to replace it you must replace the entire valve cover as it is built in.

[Radioactive]

The tech @ BMW did mention this as a possibly, but was very vague. Your explaination is far superior. If the noise does return I'll give your test suggestion a try. Thanks