Bill, I decided not to flush it ,other than with water. For one thing its impossible to get to the engine block drain, without removing things that have not been moved in 24 years, better to leave sleeping dogs lie. That sleeve I emailed you about on the heat exchanger plays an important role , it forces the water (antifreeze) to go through the first two openings in the tube and then out the other end which insures the heat transfer . Not having a sleeve allowed some of my water to bypass the H/E thus the overheating. We just came in from running the snot out the boat , like 2800 rpm for twenty minute and it never went above 190 ,problem solved. So if you have a Volvo TMD22  and have persistent overheating , check to see if you have this small rubber sleeve that slides over the H/E tube , mine had fallen apart over time. Also I bought parts that were $288 for a Volvo here (end caps), for $48 through Parts4Engines  in the UK , but for a Perkins M80T, so buy Perkins not Volvo parts,tip of the day!