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..
more later..