Yanmar 2GM20F

[Frank Brdimus]

I drained my engine's coolant and replace it with a fresh solution (40% anti-freeze). My problem is that the engine now over heats after 10 minutes on idle. My next move was to replace the thermostat but that did not help.What should be my next move - flush the stystem and use a cleaner. If so what what cleaner should be used??Other suggestions????????

 

[Eric Lorgus]

You probably got air in the system

Frank: I've heard that draining/refilling the fresh water coolant is tricky business, because air can get in the system. That's all I know. If you changed it just as routine P.M., & engine wasn't overheating before the change, it's not likely your problem is the thermostat or any other component failure.

 

[Kevin]

My Experience

I replaced my coolant on my 86 28.5 as a preventive measure and the result was instant overheating. It turned out that the filler tube had a "high spot" and this caused an air lock to occur and only about 50% of the volume of coolant to enter the engine. Fortunately I figured it out before any real damage happened. The repair was to hold down the filler tube above the engine and have my wife finish the filling. Also it would have been better to know the fill volume in the first place, so I would have realised the issue before running the engine.

 

[Ken K]

Your overheating is caused by trapped air. To solve this problem, separate one of the heat exchange hoses on the engine that goes to your hot water heater. Remove the cap, raise the hose above the engine. put a funnel in the hose and add more coolant until coolant appears in the open hose fitting on the engine. This used to happen to me whenever I changed the coolant.