Rotten eggs smell with bottom engine rattling noises

[Matyoka]

Howdy folks,

Things always happen when unexpected as I was thinking of trading in my fully loaded 2011 50i just 2 weeks ago. The N63 engine went through the massive recall back in 2015-16 if I remember correctly and I didn't really wanted to get rid of it for a while. Plugs and ignition coils were done as well circa 2017... The car has had a coolant leak I addressed just 3 weeks ago, clamps were loose on the top lines so that was pretty easy. Last Sunday morning started it up and a rotten egg smell hit me through the vents. I figured I might have picked up a rodent and did not pay too much attention. Took the car on a 250 mile trip on Monday and some rattling was starting to occur just a couple of minutes from my house. Pulled it on the ramps when I arrived home and seems like its on the bottom of the engine perhaps towards the left side if facing the car. To get to the point, I returned from a trip last night and started the car after sitting for a week... Same rotten egg smell hit me right away and bottom rattle present but not all the time, comes and goes even when driving it on a short distance(mail box). I also noticed that my power steering reservoir rattles like hell when touched, not sure what could cause it. In any event, I know the Catalytic converter will come up as number 1 culprit. I will fuel up today and see if that will cause any changes... but I am sure that's not the cause. Combined with the rattles, I hopefully have something else going on and thanks for your time accorded to this reading.

Lev