I found a leak in the closed side of the heat exchanger/manifold tank on top of my unit. Must have 10 connections on it. Feared making it worse so I temporarily fixed it with a throughbolt and JBweld (miracle product!). (Might be too good and will be there forever!) Now want to drain all the old nasty fluid (it must be horrible if it allowed corrosion like I found and when I opened the bleed fitting on top some nasty looking fluid oozed out) and am not sure of the best methodology to drain and FLUSH it. Anybody done this? Guidance? I have a gallon of antifreeze ready to go. Thanks in advance, Jim

<snip> > done this? Guidance? I have a gallon of antifreeze ready to go. Thanks in > advance, Jim > Jim, I replaced a leaking exchanger on my 12.5BTDA a year ago, had a leak between the seawater and closed side- (at about 1100 hrs). Make sure you don't have seawater in the engine cooling side before you put a bunch of time into flushing it. If you're considering a flush out, it seems now might be the time to do a pressure test to assess the integrity of the system. To flush mine once the exchanger was replaced, I removed the thermostat, filled the engine side with a strong mix of TSP, and ran the genset loaded to heat it up. I drained the TSP solution, flushed from the bottom, drained then re-filled with plain water, ran up to temps, drained, flushed. I did the freshwater run cycle twice, so once with the TSP, then twice with freshwater with a flush out in between. I wanted to be sure the seawater was gone before I put it back into service. After that, I drained the final time and did the final fill with antifreeze mix. As always YMMV -- Steve Sipe Solo 4303 /"Maerin"/ On the "Down East Loop" Miramichi, NB