I do have an OBDII reader and it's thrown codes since I bought it last summer due to the previous owner attempting to upgrade parts but taking shortcuts instead of installing the aftermarket parts correctly. I'll try to get a screen shot of the codes later today and upload them here. I also have replaced the small PCV membrane and that small cap that is on the back left of the value cover before. I'm missing the sensor plug that goes from the air intake to the PCV tube due to the previous owner and their shortcuts so I'm getting a code for that. I'm also getting codes for misfiring in every cylinder which is why I replaced the spark plugs. I love my mini but I have had issue after issue with it since the day I bought it.

Odd sweet smell 'could be' indicative of coolant in the oil but I would think the oil would look murky. I wonder if it could be the valve cover...  The pcv system and a oil-water-separator is incorporated into the valve cover.

Loss of power could be a vacuum leak or maybe a wastegate (in the turbo) that is not closing all the way.

Have you checked to see if there are any fault codes recorded into the computer?

I live in Iowa so it can get pretty cold during the winter. I did drain the oil even tho I just changed it not too long ago and it was surprisingly really dark like it hadn't been changed in awhile. I didn't notice anything unusual in the oil such as coolant or water but it did have an odd sweet smell which leads me to believe it could be coolant. Hopefully this gives a little more insight to the issue I'm having.

It may depend on where you live and how much sludge you have. On much older style engines (e.g. classic Minis), air is admitted into the crankcase and valve area for crankcase ventilation. In cold, damp areas the air will contain moisture which condenses when the engine gets cold. When the engine runs, the moisture is whipped into an emulsion that can look like dark mayonnaise. It was not unusual to see it around the oil filler cap which on older engines was on the valve cover.

If it is excessive, you have a problem. It possibly could be something simpler than the head gasket, such as a break or bad connection in the crankcase ventilation system allowing too much air in.

Hey everyone. I need help! I have a 2012 countryman s all4 and currently I have been having some issues with it not putting out the full power that it's supposed to. I have tried changing the spark plugs and the valve cover seal with no improvement. I did notice that when I removed the valve cover that there was whitesh/tan sludge on the inside of it. I was told by a couple friends that it's most likely a bad head gasket. I really hope that it's not and the sludge could be possibly caused by an issue that won't be as expensive or time consuming to repair. Please give me some good news!