[jefe2000]

I've been diving down the rabbit hole of learning all about oil filter housing (OFH) gasket leaks (and gasket replacement), serpentine belt (and tensioner and pulley) replacement intervals and procedures, and crank seal guards for my M2's N55 engine. There's a lot to learn, especially for someone new to DIY car maintenance. (I'm sure grateful for all the forum posts and YouTube video procedures!)

Part of this was to go out to the garage, lift the hood, and examine the OFH and serpentine belt. Wonderfully, all look good to my eye! No leaks or oil anywhere to be see on or below the OFH. The belt is dry, clean, and there are no cracks or rips anywhere that I could see. I rubbed my finger along both exposed sides of the belt and along the exposed portions of the pulleys: no slick surfaces or oil on my fingers, just some dust. I still need to start up the car and watch the belt run, to make sure it doesn't look extra loose or anything. I have 5 years and 34K miles on this belt, so I expect it's fine.

While poking around with my LED flashlight, I noticed a circular area (on the engine block?) just behind the serpentine belt tensioner. It looks like there's a small amount of seepage at the bottom of this circular area. And it looks like the seepage might have run a small ways down the block.

I don't know what this circular area is and whether seepage is normal/expected at this part of the engine. Any ideas on what this circular area behind the belt tensioner is?

See attached photos of the circular area and a close-up of the seepage.

I'll take any input. Thanks in advance!

[///393]

These are the threads I’m here for. Curious what my friend/wrench says that’s a BMW master tech. I’ll float this his way and see what feedback I can get.

[jefe2000]

Excellent, thanks wilson kop. I appreciate it!

[XutvJet]

It's the vacuum pump cover. My M235 (basically the same N55 as yours) has weeped oil at that spot since 2017. There's been no change over time. I just wipe it once a year and continue to monitor it.

Replacement is pretty easy if it bothers you. Remove the accessory belt and tensioner which literally take 5-10 minutes and then pry the old cover out or carefully run a couple of screws into the plastic cover and pull the cover out. Then pop in the new cover. The cover is like $16 - BMW Part Number 11117530262

[jefe2000]

Ah ha! That’s exactly what I was hoping to read. I’ll clean and monitor it.