My 2GM20s with ethylene glycol antifreeze cooling
loops and heat exchangers have ball valve pigots on the side for draining out the cooling
antifreeze. We replace with new antifreeze, then run propylene glycol through the heat exchanger
to exhaust as mentioned above.
The propylene glycol sold by Canadian Tire is for minus 50, and sells for 8-9 dollars for 4 litres. You can both afford to waste some, and afford some dilution with the price
You should go to Yanmarhelp.com with your question, and for other good info.