My problem is that I have a thin film of oil on the corner of the block near the a/c compressor/alternator. 2012 R55 S.

I think these are timing chain guide bearing bolts. They're my best guess of what could be leaking.
I'm wondering if they're known to leak oil, and if so, how do they seal? I haven't seen gaskets for them.
I see them on page 117-5 and 117-11 of the Bentley manual labelled as "timing chain guide rail and tensioner guide rail bearing bolts" - I was hoping they were plugs that you removed to access the bolts, but I think they literally hold the chain guides in place.




I just did the crank seal 250 miles ago. It was probably leaking prior. I thoroughly cleaned the engine bay at the same time.
I did an inspection today - the crank seal looks great 👍 Dry. Thanks for the guide.
I pulled the wheel liner back some more & saw the wet area around the front corner of the engine. At least it's fresh clean oil, but hard to tell where it's coming from.


The car has had small oil leak(s) for awhile. Lots of caked oil/dirt on the engine. Never enough to drip on the ground. I'm taking care of some maintenance this season- crank seal, engine mounts, belt/filters, and oil cooler gaskets, and want to fix the leaks.

The wiring harness for the alternator is wet. Where it runs below the valve cover, between the engine mount and block. I am not 100% sure if this is new wetness or old, since it's in a hard to clean area.
The rubber boot on the tensioner for the friction pulley is wet looking. It could be old, it's in a hard to clear area, and lots of nooks and crannies for oil to hide in that area.
The bottom of the head is wet (the bottom surface of the head that overhangs above the alternator). This could be old, but it's very wet (also dirty/grimy though)
There is a torx bung below the vanos solenoid that looks suspiciously clean/shiny. As well as the through-hole for the engine mount bolt next to it.
The major wetness I see is around the a/c / alternator area of the timing chain cover
The dipstick tube seal looks dry.
The vanos solenoid seal next to it looks dry.
The valve cover gasket looks dry (maybe a litttttle wet, but doesn't look like it would cause this)
The oil pan gasket doesn't seem likely since the wetness is above it.
The other option is... the split block for the crankshaft or head gasket. ha ha ha tell me about other options ha ha ha.


On a semi-related note:
The oil cooler gaskets, or/and turbo oil lines are probably leaking. There is a small run of oil down the front facing side of the trans near the downpipe (assumed it was rear main seal at first)
I think this leak is only a few months old, because I haven't noticed the trans wetness before, and the turbo area near the valve cover looks clean. I just did the driver side trans mount & the transmission top surface is still clean from when I cleaned it 4 months ago doing the coolant t-fitting.
I have the oil cooler gaskets in hand (both sets) & was planning to install them once I receive the passenger engine mount and turbo oil lines.
I have a hard time believing that they are leaking in a way that puts oil around the a/c compressor or alternator (especially on the passenger side face of the block after just 2 weeks)
The front of the engine (behind the exhaust manifold) is caked in dry dirt/oil, so I assume something has been leaking in this area previously. I can't access that enough to clean it up until I do the oil cooler stuff.

I am 50% sure the .... timing chain tensioner bolt(?) it is on the back of the engine, at the top passenger corner, is leaking a tiny bit. Or has been in the past. There's caked on grime around that area. It doesn't seem wet right now, and I don't think it would leak towards the front of the car.


I'm about to do the passenger engine mount, so I guess it would be a good time to address the guide rail bolts if they're leaking. I'm guessing I need the cam holder tool... I guess I should look up the car's history & see if the cassette assembly + tensioner has ever been replaced...
Sure is fun to drive though(:

 

This is a lot of leaking for a 2012.

For the driver side transmission side, could also be the vacuum pump gasket. Was leaking like wild on my R57. There are gasket sets to be found.

The guide bolts have rubber gaskets on the bolts. Those are supposed to be single use AFAIK, so maybe that's why those are not mentioned separately.

The tensioner is a metal gasket I believe.

If you plan to put a new tensioner on and renew the guide bolts, buy a cheap camshaft holder. The chances the chain could jump when the tensioner bolt is out is high. Then you need to redo timing.

Make sure to read up what all is single use hardware.

and check your PCV system first before doing anything else. Not that it's just pressing out the oil because of blocked ports/clogged membranes and crankcase pressure.

 

Also, did you put a new valve cover gasket on, with properly using ATV on the driver's side? They often look dry, but it's hot up there, and the oil gets thin.

 

Thanks, I see the washers for the guide bolts on this guide here- https://www.bmwrepairguide.com/mini-...er-n12-engine/
I'll try torqueing them when I do the engine mount, and I can inspect the area with the mount out. Then I guess it'll be time for the whole timing chain procedure if it doesn't fix the leak.
Fortunately the leaks sound worse than they are. They're more like seaps. They really manage to cake the engine in dirt though.

I haven't touched the valve cover yet, other than last year I changed the PCV rubber diaphragm (thought I had a whistling noise), old one didn't look bad. But the noise seemed to get better.
I would like to verify the valve cover is functioning as intended though. I think the oil cap and breather tube leak more than they should. That's another thing to add to the list.

 

Solved- it was the upper guide bolt. It took 1.25 turns just to snug it up finger tight, that's a good reminder to not ignore leaks.
This can be inspected without removing anything. Shine a light down between the mount/head, and look for a pool of oil on the ridge under the guide bolt. I don't think a crank seal will get oil that high. It never dripped on the ground, but it did leak enough while running to blow back onto the subframe. You can also feel the bottom side of the head where it overhangs the alternator for collected oil. I backed the guide bolt off a couple turns to make sure the crush washer was actually in there and in decent condition before torqueing it and putting everything back together.
I couldn't find the torque spec. I did 30-35ftlbs. I think that's tooo much, there are stories of bolts breaking. The lower guide bolts were still tight.
I pulled the water pump pulley, friction pulley, crank pulley, tensioner, and cleaned them all well. The pulleys and belt had layers of grime on them. Got to install a new belt for the leak-free engine finally. New mount feels great too.
It's been a week & the timing cover is still clean & dry.

Helpful links-
https://new.minimania.com/Mini_Cooper_Cold_Start_Rattle
https://parts.seattlemini.com/a/MINI...s/11_4585.html
https://parts.seattlemini.com/a/MINI...n/11_4545.html
https://parts.seattlemini.com/a/MINI...1_6750.html#10
https://www.realoem.com/bmw/enUS/sho...diagId=11_3951

rmeuropean looks to be the best place to buy bolts & gaskets individually. I think this gasket would have been 11317550461. I just torqued the bolt & will keep an eye on it.