Newby here so sorry for this dumb question. Wish to flush collant from my 2004 H6. Manual says remove plastic sump cover but on the cover there are two access/inspection holes with small covers; two rivits and what looks like a catch. Try as I might I cannot "open" the cover/s to get access to what I think should be the drain tap. Any tips or do I need to remove the whole cover. Also, no mention of an air bleed tap/vent for the final fill; is there one or will careful filling & topups suffice?