Block drains on my 4.5 look just like 19mm bolts. There is one on each side. Remove the plug and I can almost guarantee nothing will come out. Once the plugs are out take a small screw driver or awl and poke it through the crud build up that is sealing the drain. I promise water will come out once you have the plug of crud cleared.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.