Coolant Replacement - Diesel Yanmar

[pariseaux]

I have a 3GM30F Yanmar 2002 and am changing the coolant for the first time since purchasing the boat. The old coolant is a red rusty color (see picture). I'm not sure what coolant/antifreeze was used by the previous owner. I'm planning to replace with Yanmar Ultralife 3G30 (recommended by my Yanmar dealer in St Pete). Can anyone give advice on whether you think the old coolant needs to be drained/flushed before I put in the new coolant? I know you have to flush it when the previous coolant is green in color, but this appears to be the red antifreeze (although the color does seem too dark).

If you think the coolant needs to be flushed, can anyone direct me on where the petcock for the drain in the attached picture is? I found the petcock for the second drain that is further towards the aft, but this drain (shown with a red arrow) appears to have no petcock.

Any help would be greatly appreciated!

 

[Rick D]

I may be mistaken, but I believe the one in the last photo opens by unscrewing the knob on the bottom. If it were me, I would flush that system. It's pretty nasty anyway, and you'll be better served with the new antifreeze with a flush anyway. Good luck!

 

[TENACITY CS36T]

Good idea to flush extremely well when putting in new and likely a different type of coolant, otherwise the old can react with the new in a negative way.

 

[Claude L.-Auger]

There are 3 petcocks on the 3GM30F. The one shown on the last picture (and yes the knob under it opens it), and 2 on the other side of the engine: one right above the fuel pump, with the same kind of knob, and one near the rear end of the exhaust manifold. Flush thoroughly before putting in new antifreeze.

 

[NYSail]

What's a good flushing product

 

[Ken13559]

What I recently did was run the engine hot, drain out coolant and top with water. Continue to run and drain till the water is not colored by remnant coolant. Then drain water and top up with new coolant. With engine hot the temp valve would open hence old coolant can be circulated out. Not aware of other method if there is.

 

[woodster]

What I recently did was run the engine hot, drain out coolant and top with water. Continue to run and drain till the water is not colored by remnant coolant. Then drain water and top up with new coolant. With engine hot the temp valve would open hence old coolant can be circulated out. Not aware of other method if there is.

keep some extra gaskets for the thermostat housing and remove the t stat and run it with out one ...thats also a good time to check the t stat while its out

 

[Ken13559]

keep some extra gaskets for the thermostat housing and remove the t stat and run it with out one ...thats also a good time to check the t stat while its out

Thanks . That sure get the old coolant out faster.