Oil pressure is normal as well. The mechanic hasn't diagnosed anything, all he told me was that it definitely wasn't coming from the top and that he'd have to dig deeper into the engine. The only reason I'm entertaining the idea of a rebuild is that for the expense of getting into the bottom end and diagnosing, not to mention repairing, I'd rather just put that money towards fixing everything and start with a like new engine. I've taken it to two very reputable Mercedes mechanics who have both told me that it's not something that they can tell simply by looking at it. I do appreciate everyone's help trying to diagnose, and I'll probably end up going that route, but for now I'd just like to know how realistic it is to do a diy rebuild if I'm patient and am willing to put the car out of commission for a few months. If it is realistic, I'd love some resources that would help guide me through it.