I went down to the boat armed to change the coolant for the first time since owning the boat. It is overdue. I found the drain stop cock on the port side of the motor, and once ready to catch the old coolant turned it. It was very difficult to turn (in needed a pliers) and then nothing came out. I turned it numerous times -- nothing came out. Has anyone else had this problem? Is the stop cock bad? Any help would be appreciated.
Problem changing coolant in Yanmmar 2GM20F
- Thread starter dph123
- Start date
In case you don't have it, attached are photos of the cooling system arrangement for the 2GM engines. Yes, as already suggested, the drain plug is probably blocked. That is what I encountered the first time I went to flush and change my coolant after I bought my boat 10 years ago. As you can see in the picture, the drain tube is at right angles to the drain plug. So if you run a wire up the tube but the blockage is at the engine side of the drain plug, the wire will not clear it out. Believe it or not, what work for me was I blew on the end of the tube with the oil drain plug open. Of course simultaneously with stopping the blowstop, very important to get your mouth out of the way to avoid the rush of antifreeze! If you are able to pull the tube up above the engine, that would be best. Maybe one of those narrow spouted plastic squeezable ketchup bottles could be utilized instead of one's mouth. Another way to force air or water up the tube to hopefully free the blockage.
Removing the entire drain plug from the engine block would afford the best cleaning. But then the existing antifreeze would rush out of the engine block quite quickly. A big mess probably.
Removing the entire drain plug from the engine block would afford the best cleaning. But then the existing antifreeze would rush out of the engine block quite quickly. A big mess probably.
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I hope the drain you were opening was on the starboard side of the engine or who knows what you were into. Don't worry, there were only drains on the starboard side last week when I was working on mine.
The manual is confusing as it shows a 3GM30F which is different.
As others have said, the easiest solution is to remove the drain valve. Make sure you leave the filler cap in place and this will slow (reduce) the amount of coolant discharged and have some sort of cork ready to temporarily plug the hole. Remove the filler cap later for a complete AF removal.
Do all three drain cocks while you are down there as the 2GM has two drains for AF and one for the seawater heat exchanger. Bet money they're all plugged.
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Ralph,
Good catch about the Opening Poster working on the port side drain cock!
For the OP, that one drains the coolant from the combined exhaust manifold / header tank unit. If the GM series is like my QM, not much coolant is over there as compared to the engine block ... which is drained from the starboard cock as Ralph describes.
Regarding the diagrams I attached to my previous post, I photoed them from the after market Seloc manual that I have on my boat where I am now. (The official Yanmar GM series service manual is in my garage.) The Seloc manual labels the diagram as a 3HM series... With a notation that the 2GM and 3GM are similar. Hope that it assists anyway with orientation.
If I might suggest... Best to avoid using pliers to open and close the valves. They are made of brass. Pliers will round off the hexagon nut shape pretty quick. Depending on how much room you have in your engine compartment, metric box wrenches or sockets are preferred. Also there are two thread components to the valves. Opening or closing the smaller end nut controls the drain of the fluid. Counter-clockwise, the larger hex shape of the valve body removes the valve from the engine block. The first time I changed my antifreeze, the small drain control nut was very tight. Trying to loosen it, the entire valve started to unscrew. I needed to hold the valve from rotating with an open-ended wrench. So that I could break free the smaller drain nut.
Good catch about the Opening Poster working on the port side drain cock!
For the OP, that one drains the coolant from the combined exhaust manifold / header tank unit. If the GM series is like my QM, not much coolant is over there as compared to the engine block ... which is drained from the starboard cock as Ralph describes.
Regarding the diagrams I attached to my previous post, I photoed them from the after market Seloc manual that I have on my boat where I am now. (The official Yanmar GM series service manual is in my garage.) The Seloc manual labels the diagram as a 3HM series... With a notation that the 2GM and 3GM are similar. Hope that it assists anyway with orientation.
If I might suggest... Best to avoid using pliers to open and close the valves. They are made of brass. Pliers will round off the hexagon nut shape pretty quick. Depending on how much room you have in your engine compartment, metric box wrenches or sockets are preferred. Also there are two thread components to the valves. Opening or closing the smaller end nut controls the drain of the fluid. Counter-clockwise, the larger hex shape of the valve body removes the valve from the engine block. The first time I changed my antifreeze, the small drain control nut was very tight. Trying to loosen it, the entire valve started to unscrew. I needed to hold the valve from rotating with an open-ended wrench. So that I could break free the smaller drain nut.
Thanks all for the help. The drain cock I found was the highest (it was on the starboard side -- a duh moment). I found the other two with your help and Ralph's photo. They both opened with ease and drained. Once I got back to the high one (I had to remove it to clear it), only a small amount came out. The rest went smoothly. Thanks, again!
Watch for a vapor lock. I drained mine, refilled and started off for a sail and got an overheat. Had to open the valve on the starboard side until fluid ran out. I had new fluid, but there was only air in the engine manifold.