So I flushed my coolant today and bought 5 gallons of 50/50 to prepare for what I understood to be about a 17 liter coolant capacity in the radiator. When I drained, I'm not sure how much I got out but it wasn't even close to 17 liters. I filled with distilled water, ran the engine with heat on high and drained again. And again. The last time the drained water was pretty much clear. So I filled with my 50/50 and to my surprise, I was only able to use about 2 gallons before the radiator was full. What's the deal here? Could there really be that much water trapped in the engine block? And if there is, shouldn't I have used full strength coolant concentrate since it's going to get diluted anyway with the water in that's in the engine block?