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Old 12-11-2010, 00:41   #1
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Yanmar 2GM20F Coolant Change

I need to change the coolant on my motor and been trying to find out where to drain the old coolant from.
Im sure there is plenty of 2GM20's out there.
Thanks
Reiner
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Old 13-11-2010, 04:13   #2
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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..
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Old 13-11-2010, 05:26   #3
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Thanks for that MitchM.
I do have a manual but couldn't find any information on how to drain the coolant. I did get the red stuff from Yanmar but done nothing with it so far.
Cheers
Reiner
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Old 13-11-2010, 06:05   #4
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On the 3GM30F, one drain cock is under the heat exchanger and one is low on other side of block . Mine have round grooved knobs maybe 1/2 inch diameter and about 3/4 inch tall.
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Old 13-11-2010, 06:45   #5
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The two knobs are raw sea water drain and coolant drain. Open one a bit. If what comes out is pink or yellow, that's it. If not, try the other one. Then you know you have the right one. Be sure you use the coolant type recomended by Yanmar as less corrosive. (I'd tell you, but I don't have my book with me, it's on the boat).
Good luck, Mark
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Old 13-11-2010, 18:51   #6
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The raw water drain tap on my Yanmar has a tee handle rather than the round knob, but undoubtably all types are possible.
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