I don't know why, but I'm feeling really proud of myself. I was able to flush and fill the freshwater, aka heat exchange closed loop system coolant on my Hunter's Yanmar 2GM20F. I had no idea when it was done last. Not in the few years I've owned her.
I did a lot of researching here on SBO of how others have advised and done this. I had some of the same issues: my drain cock for the heat exchanger was plugged. I stuck a small phillips screwdriver in the valve behind the knob and it came out coated in black gunk! I was able to clean it out and get flow. On my model, both the exchanger and the block drains are on the starboard side within inches of each other. Also, my overflow tank was full of what looked like orange mud that I had to clean out. I figured I'd be flushing the system before refilling it. FWIW, I used Blue Devil Radiator Flush because that was all Autozone carried. I flushed the system per the instructions making sure to run fresh water after to get the chemical out. Then I filled, drained filled again with extended life antifreeze until clean mix was coming out.
Next problem was getting the air out. The alarm went off twice while I waited for the tstat to open and allow coolant to mix properly. I had the familiar air pocket behind the tstat situation. I tried the trick of loosening hoses to let air escape. That wasn't working. Since it's the highest part of the system, I cracked open the tstat housing to "burp" it, This worked! I ran the engine a long time under load to make sure it wouldn't overheat again. I also checked the specific gravity to be sure my mix was correct for our region. There was a slim chance that water in the system might have diluted it. Everything checked out. I now have a clean, effective system and a baseline for regular maintenance in the future. I keep a log of everything I do on Bella.
I did a lot of researching here on SBO of how others have advised and done this. I had some of the same issues: my drain cock for the heat exchanger was plugged. I stuck a small phillips screwdriver in the valve behind the knob and it came out coated in black gunk! I was able to clean it out and get flow. On my model, both the exchanger and the block drains are on the starboard side within inches of each other. Also, my overflow tank was full of what looked like orange mud that I had to clean out. I figured I'd be flushing the system before refilling it. FWIW, I used Blue Devil Radiator Flush because that was all Autozone carried. I flushed the system per the instructions making sure to run fresh water after to get the chemical out. Then I filled, drained filled again with extended life antifreeze until clean mix was coming out.
Next problem was getting the air out. The alarm went off twice while I waited for the tstat to open and allow coolant to mix properly. I had the familiar air pocket behind the tstat situation. I tried the trick of loosening hoses to let air escape. That wasn't working. Since it's the highest part of the system, I cracked open the tstat housing to "burp" it, This worked! I ran the engine a long time under load to make sure it wouldn't overheat again. I also checked the specific gravity to be sure my mix was correct for our region. There was a slim chance that water in the system might have diluted it. Everything checked out. I now have a clean, effective system and a baseline for regular maintenance in the future. I keep a log of everything I do on Bella.
