do you have the owner or service manuals
? my recollection is that there are 2 or 3 drain valves for the antifreeze
, located on the engine
block . they look like little t's or spigots and usually have transparent plastic hoses attached to them so the coolant drains into the bilge
and not onto the alternator
belt or engine
mounts or electrical parts
. turn the spigot handles left=loose to open them.
be sure to take the radiator cap off it won't drain.
i'll look in my 2 gm manuals
tomorrow, they aren't where i am right now.
when you change coolant it's a good idea to flush the system using a coolant flush. especially important if you are changing from the old 'green' antifreeze
to the yanmar
recommended red coolant 'Dexcool' . the old green coolants were found to precipitate out too much silicate salt
which coats the yanmar
heat exchanger tubes and reduced cooling
efficiency, so yanmar now recommends RED dexcool style coolant not green . but you can't mix the red and green together..