Volvo Penta D2-55 Coolant Fill

[MJH]

I'm completing a Heat Exchanger replacement to an "F" model exchanger and will soon load new coolant. Boat has a Water Heater and also a small salon Hydronic Heater running off the engine.

Besides loading the coolant slowly what is the best procedure to insure there is no air in the lines when I am done?

[DougR]

As you stated, fill the coolant slowly, allowing air bubbles to make their way out.

Then start and run the engine with some load on it to get it warm enough to open the thermostat, all the time with the fill cap off the tank and keeping an eye on the coolant level in the tank. Top up if the level drops when the thermostat opens.

After everything stabilizes, put the cap on and let the engine cool down. Recheck and top up if necessary.

With all the external volume that you have, you might be close to needing an auxiliary expansion tank, but if it wasn’t a problem with the original HE , it won’t be a problem with the new one.