2011 135i n55 - Squeal after coming back down to idle

[AlexHall886]

I have been chasing my tail on this one… After revving my car to 2500-3000rpm, and once the car settles down to idle, while stationary, I get a loud belt type squeal for just a couple of seconds. It will only do it again if I rev it again. I discovered it shortly after I got the car. I was just screwing around in my garage revving it and it happened. I’ve since replaced the belt, tensioner, idler pulleys, and ac compressor. The car is modified with an mhd tune, vrsf intercooler, catless downpipe, some sort of exhaust, and arm intercooler hoses. When digging into the car, I found that the belt and ac compressor pulley had rubbed a groove into the cold side intercooler hose. I pushed the hose onto the intercooler as much as possible and gained enough clearance to where it didn’t rub. After discovering this, I replaced the belt, pulleys, and tensioner. To my disappointment, the noise didn’t go away. I already knew I had a knocking coming from what I believe to be the ac compressor with the ac on, so I went ahead and replaced that tonight. I’m going to work tomorrow to charge the ac, hopefully at least the knock with the ac on will be gone. I also thought the compressor would fix the squeal, it did not. I’m really stumped on what it could be. I can post a video if necessary, but it is pretty straightforward. I rev it to 3000 rpm, it crackles and pops, settles down to idle, and emits a belt squeal.

[bnace10]

Likely the PCV valve is bad.

Mine does this consistently once oil is up to temp both on decel down to idle, and at idle.

[AlexHall886]

Originally Posted by bnace10

Likely the PCV valve is bad.

Mine does this consistently once oil is up to temp both on decel down to idle, and at idle.

Just watched a video and the guy has the exact same noise, thank you!