So today I finished off the major maintenance with a cooling system overhaul. Pretty much a lot easier to do since the zhp had an electric fan. The only thing that didn't seem right was the expansion tank sitting down didn't look flush but I guess that's how the engineers designed it. The coolant was brown/yellow assuming that some oil was leaking in the coolant and/or that the coolant the p/o put in wasn't bmw coolant. I'll have to check up again in a week to see if anything seems strange. Would love some input into the matter guys