Yanmar 3GM30F coolant in fresh water exchanger

[WacoLen]

While replacing my impeller, for the first time, I had to remove the end cover of the heat exchanger to find the broken pieces. I drained the fresh water from the heat exchanger one week and retuned the next week with new gaskets. After removing the cover and old seal on the forward end of the heat exchanger, there was a slow leak of coolant out the bottom of the exchanger. I was able to catch most of it and put it back in the top.

If I understand how the exchanger works. There should not be coolant in the fresh water part of the exchanger because I thought the coolant side of the heat exchanger was a closed system.

Does this mean I have a leak in my exchanger tubes? Or is the coolant side not a closed system?

Yanmar 3GM30F

Leonard Hooks
SV Revelation, Catalina 320 #856
Waco

[jkishel]

“Fresh Water” refers to the fluid in the closed, pressurized circuit, which should be a 50-50 coolant/fresh water mix. “Raw Water” is the sea water in the open circuit that runs from the sea water through hull to the exhaust system. Fresh water (coolant) circulates around the heat exchanger and raw water (sea water) flows through the heat exchanger. It sounds like the end cap seal is leaking coolant under pressure. If the heat exchanger itself is leaking, coolant under pressure will flow into the heat exchanger and be lost out the exhaust. Carefully fit the end cap seals around the heat exchanger and the coolant tank before tightening the clamps.