2010 R25 SC Coolant Change

[Gunner065]

Hi folks, hope all is well and safe.

So we purchased our R25 from its original owner in June 2020. The past two years, I replaced 2-3 liters of coolant annually (during lay-up before winter), but I have never been able to get change more than that.

The YANMAR 4BY2-150 Owner's Manual directs to remove the Heat Exchanger to access the cylinder block drain plug. Since I do this on an annual basis, is there a way to remove most of the coolant without removing the heat exchanger?

Any and all suggestions would be greatly appreciated.

 

[knotflying]

There is another petcock slightly lower on the rear of the engine below the turbo almost in line with the starboard engine mount. You still will not get all the fluid out, probably about half. Hence, I would change the antifreeze every two years, which I seem to remember was about half the time suggested in the periodic maintenance. Removing the heat exchanger, IMO, is crazy! You are only looking for trouble if you do that.

 

[NorthernFocus]

I have a different engine but just use a vacuum pump designed for pulling oil out through the dip stick. I simply put the suction tube in through the coolant fill cap. I just change out a gallon every season and call it good. The most important thing is making sure the antifreeze ratio is right and that the additives that prevent corrosion aren't depleted. Never adding straight water accomplishes the first and refreshing the coolant with even a partial change takes care of the second.

 

[GaylesFaerie]

There is another petcock

I tried looking for that petcock and another one mentioned to be on the starboard side of my engine (4BY2 180). Can you confirm if these photos show them? These are barbed fittings but I've not seen petcocks like these and I'm also confused at how they work. I've not seen a nut of that shape (four lobes with convex indents between them) and it almost looks like if I unscrew it, the whole petcock will come out. And it looks like one needs a special wrench given the nut shape. As I look closely at the photos, I can see the first one has never been touched, while the second has some bite marks in it (wrong wrench?).

Aft petcock under turbo and anode bolt looking forward:
https://share.icloud.com/photos/051CjD9 ... 6BorafqhzQ

Same petcock looking to port:
https://share.icloud.com/photos/0768L9Z ... VY9OyVSCxw

Better focus of same petcock looking to port:
https://share.icloud.com/photos/0d7eciB ... a8a3wbHlvg

Petcock on side of heat exchanger:
https://share.icloud.com/photos/0f9XXfa ... kSp4woMTEQ

Thanks, Gary

 

[knotflying]

Yes, those are the petcocks. They are plastic so be careful. I am not sure if there is a special wrench, but I used a plier with a slight turn on the first loosening and after that just my hand.

 

[GaylesFaerie]

Thanks Mike. I assume lefty loosey and righy tighty? And roughly how many turns to get it flowing well? Gary

 

[knotflying]

Correct on loosening and tightening. A few turns and the antifreeze should start running out. I attached a tube and have two empty gallon jugs available. Put the jug into bilge as low as possible by shaft. Place on angle to be lower than petcock. I also open the fill cap to get good flow. I used an electric pump once and you don't get any more out using it. I just replaced every other year.

 

[GaylesFaerie]

Thanks Mike. Appreciate the little details. Gary