[TitaniumTT]

Don't know about the coolant seals and vinegar. Maybe get an old seal and drop it in some vinegar and see what happens?

What I've done in the past with varying degrees of success is to drain the coolant, fill with water and Cascade.... yeah, dishwashing soap. Needs to be dishwashing soap as you don't want it to bubble. Run the thing for a few days, drain, pressure flush the system - a garden hose and some adapters work well, then rinse and repeat. Did this for a month in my truck and it cleaned it out prettye damn well. When flushing though, you want to isolate everything. Meaning, flush the engine with the heater core and rad hoses OFF. Flush the rad alone and flush the heater core alone. Otherwise, you're just passing shit from one location to the other.

Also, once you're done doing it one way, do it in reverse.

I've also found that no matter how clean the engine is, how many times you flush it out, the water can come out clean enough to drink, when you pop the block open, there will be shit EVERYWHERE. Kinda makes me wonder if how many of these strangely blown engines are related to simple hotspots.