Yanmar Engine Overheating?

[westwinds]

Originally Posted by Capt.Alex

Could be a small amount of scale in the heat exchanger. It may be time for a descaling bath.

That's a good point. The engine does go above the temperature that the thermostat is all the way open when the engine is operated at full RPM. This indicates to me that the heat exchanger is not getting rid of the heat in the coolant like it should. I would pull the heat exchanger and take it to a radiator shop to have the exchanger hot tanked. This should remove scale both inside the tubes and on the outside of the tubes inside the exchanger where you cannot see the scale.

[chrisjs]

I would begin by tightening ALL coolant hose clamps. I had a similar issue this year during winter storage. This seems to have solved problem even though it was not obvious exactly where the seepage was from. You should also try to determine oringin by placing paper towels in appropriate locations around engine and around filler cap per previous post.

[CaptainDana]

Originally Posted by westwinds

This could just be overflow from the expansion tank past the cap where you put coolant in. However, it could also be a hose or the seal on the pump that circulates coolant throught the engine. Need to check for leaks. Most likely what you are seeing is the quarter cup you added to the expansion tank. What happens is the coolant heats up and expands forcing some of it past the cap.

If it were fuel, it would be obvious but fuel is red too. Just sayin'