thanks for all the tips. i first drained the entire system by opening the block drain (what a great feature)then i flushed the system completely until there was only clear water running through system by keeping a flow of water into the resovoir with the car running,heater on,block drain open, & return to resovoir disconnected,until the flow was clear. then i blew out the system with compressed air to get all the water out. then refilled with MB non corrosive coolant & water. ( i didn't use distilled water) the whole process was a little time consuming, but i think it worked fine.