Yanmar 3GM - draining freshwater coolant

[Crazy-Diamond]

Hello all,

I am planning to change the fresh water coolant in my Yanmar 3GM. My problem is I am unsure where to drain it from! There are two fittings on the heat exchanger that could be drains, and on the other side of the block is another fitting which I'm wondering might be a drain tap. I am not at all sure, and the information from my manual refers to two fittings that aren't there. Handy.

This first fitting is at the end of the heat exchanger and looks like a drain, with plastic tube.


This one (top of image) is under the heat exchanger, and could also be a drain.


This is on the other side of the block, is this a drain? It is the lowest one of these three candidates. If it is, how to do I undo it? Does the whole thing unbolt?


This is the manual - but I don't have these fittings.



Can anyone shed any light on this please?

Giles

 

[RobF]

Have a look at P43 of https://j109.org/docs/Yanmar_3GM30F3.pdf

 

[Crazy-Diamond]

Thanks for the link Rob. Both of those drain cocks appear to be on the heat exchanger, surely there should be one lower down, on the block?

 

[Skylark]

I have a 3JH and recently drained the fresh water/coolant. It has two drains, both with same fittings as per your picture, both fitted with a length of clear plastic tube. One is located near the heat exchanger, the other on the opposite side, near the oil dip stick.

Gravity worked reasonably well but after a while I blew into the top of the HX and this significantly improved flow (a practice probably not recommended by the H&S police ).

The plastic tube on the heat exchanger was long enough to drain into a milk bottle. The other one needed a fairly long extension. No mess. Job done, including fresh water flush, in half an hour.

 

[VicS]

Thanks for the link Rob. Both of those drain cocks appear to be on the heat exchanger, surely there should be one lower down, on the block?

I think you will find that page 15.1 of the GM service manual , which you can download from Manual Downloads | Barrus clarifies the issue.
( Use the link for 1GM10)

The drain cock on the HE end cap just drains the seawater from the HE

The draincock on the underside of the exhaust manifold drains the coolant from the HE and manifold

The coolant drain for the cylinder block is on the other side of the engine in the case of 3GM and 3HM engines

Click on the picture below to enlarge it

 

[Crazy-Diamond]

Thank you Vic for the message. So it looks like the fitting into the block in this picture is the one I need:

It does not have a drain pipe attached - should I just undo it using a spanner on the housing, and catch the water as is comes out?