Yanmar 3YM20 coolant change

[Paul8]

I have a yanmar 3ym20 (2007) and I want to change the coolant. On the port side of the engine near the front there is a valve on The fresh water coolant hose for emptying the coolant. How do you open this valve? Also on the top of the engine where the hoses for the water heater attach there is what looks like an air bleed valve. When should this valve be opened?

 

[SFS]

Have you read the manual? I don't recall using either of those valves, and I have the same engine.

 

[SG]

https://www.manualslib.com/manual/658623/Yanmar-3ym20.html?page=26#manual

Go to page 26-....

You may need to fill it once, start the engine, then let the thermostat open (alarms might sound), shut it down, then complete the filling if you don't follow the procedure.

 

[Hello Below]

I have a yanmar 3ym20 (2007) and I want to change the coolant. On the port side of the engine near the front there is a valve on The fresh water coolant hose for emptying the coolant. How do you open this valve? Also on the top of the engine where the hoses for the water heater attach there is what looks like an air bleed valve. When should this valve be opened?

Paul8, your terminology has me somewhat confused. A couple of pictures would help to show what you are referring to. But I will hazard a guess.
There is a coolant drain cock on the left hand side of the engine when facing the belt cover that can be loosened off with a standard box end wrench or socket. I believe it is a metric 10. There is also a coolant drain plug fitted on the output of the heat exchanger. This plug requires an allen wrench (or hex key). It takes a fairly large one and I believe it is a metric 6 give or take 1 size (5, 5.5 or 7). I loosen off the drain cock then open the rad cap when I replace the coolant every 2 years. I have never opened the drain plug but I'm sure that others will chime in as to when it is used.

 

[BigEasy]

These tools are required for the 3Ym30 engine; likely the same for the 2Ym20:
The coolant drain plug in the rubber coolant hose on the port side of the engine requires a 2.5mm allen wrench. Simply turn the plug counterclockwise with the allen wrench to remove it.
The drain cock on the starboard side of the engine requires a 12mm open end / box wrench.
The schrader type valve on the top of the engine is for purging air out of the system after it is refilled; depress the valve until all air escapes and clear fluid drains from the valve while the engine is running or after turning the engine off after it reaches operating temperature. Use a long handle screwdriver to depress the valve stem to prevent steam / liquid burns to your hand.
If you use a hand pump to pump coolant back into the engine & heater hoses when refilling, you will likely remove all but a negligible amount of air from the system that should purge with the engine running and the heat exchanger cap off. Hope this helps.

 

[Paul8]

Paul8, your terminology has me somewhat confused. A couple of pictures would help to show what you are referring to. But I will hazard a guess.
There is a coolant drain cock on the left hand side of the engine when facing the belt cover that can be loosened off with a standard box end wrench or socket. I believe it is a metric 10. There is also a coolant drain plug fitted on the output of the heat exchanger. This plug requires an allen wrench (or hex key). It takes a fairly large one and I believe it is a metric 6 give or take 1 size (5, 5.5 or 7). I loosen off the drain cock then open the rad cap when I replace the coolant every 2 years. I have never opened the drain plug but I'm sure that others will chime in as to when it is used.View attachment 157220

This is a big help. In your diagrams from the manual it is the coolant drainage plug that I was referring to. I did not know how to insert pictures into my post. Now I know I can use an Allen wrench to loosen the drain cock. Thanks!
Paul

 

[Paul8]

These tools are required for the 3Ym30 engine; likely the same for the 2Ym20:
The coolant drain plug in the rubber coolant hose on the port side of the engine requires a 2.5mm allen wrench. Simply turn the plug counterclockwise with the allen wrench to remove it.
The drain cock on the starboard side of the engine requires a 12mm open end / box wrench.
The schrader type valve on the top of the engine is for purging air out of the system after it is refilled; depress the valve until all air escapes and clear fluid drains from the valve while the engine is running or after turning the engine off after it reaches operating temperature. Use a long handle screwdriver to depress the valve stem to prevent steam / liquid burns to your hand.
If you use a hand pump to pump coolant back into the engine & heater hoses when refilling, you will likely remove all but a negligible amount of air from the system that should purge with the engine running and the heat exchanger cap off. Hope this helps.

This is exactly what I needed to know. Thank you very much!
Paul

 

[NYSail]

When I flush/change coolant i always remove thermostat so o can easily flush engine without having to wait for it to open..... gd time to inspect or replace it. Also makes filing easy as the hw hoses attach here and can be filed directly.

Good luck
Greg

 

[Paul8]

The coolant drain plug in the rubber coolant hose on the port side of the engine requires a 2.5mm allen wrench

I’ve tried to remove the coolant drain plug on the rubber coolant hose but it won’t come out. I’m able to turn it counterclock many times but it doesn’t want to come out all the way. Any suggestions?
Thanks,
Paul

 

[Ron20324]

... I’m able to turn it counterclock many times but it doesn’t want to come out all the way. Any suggestions?...

IIRC, IT IS A PLUG, NOT A SCREW-IN???

 

[Paul8]

This is what it looks like. There is an opening in the plug for a 2.5 mm Allen wrench.

 

[weinie]

I didn't need to use the above plug. I used only the one on starbrd side of the engine. Emptied it into a 16oz water bottle then into a bucket.

 

[Paul8]

I didn't need to use the above plug. I used only the one on starbrd side of the engine. Emptied it into a 16oz water bottle then into a bucket.

Ok, I’ll try that. Does the plug on the starboard side empty the coolant completely? I’m switching from green to red so I plan to do three flushes.

 

[weinie]

Ok, I’ll try that. Does the plug on the starboard side empty the coolant completely? I’m switching from green to red so I plan to do three flushes.

Yes. Just make sure the pressure cap is off to allow the coolant to drain. I did about 3 flushes I believe before I refilled it.

 

[BigEasy]

Paul,
My plug was definitely threaded without the as clamps pictured on your hose. To remove your plug, you’re going to have to remove the clamp to remove the plug. You can always replace the clamp with a standard hose clamp. It’s easier accessing the hose plug vs the engine plug, especially if you are going to flush the system a few times.

 

[weinie]

Paul,
My plug was definitely threaded without the as clamps pictured on your hose. To remove your plug, you’re going to have to remove the clamp to remove the plug. You can always replace the clamp with a standard hose clamp. It’s easier accessing the hose plug vs the engine plug, especially if you are going to flush the system a few times.

It's easier to get to , but my concern was that it was too high to drain a lot of the coolant.

 

[Evorbach]

was planning on changing the coolant on my 3mY20 this season as well. Not clear as to the procedure. Not sure I have the correct manuals.I have a yanmar service manual, but it doesn't read very well. From what I am reading here, I open these (or one) of these valves, open the cap and drain the system. Do you then run fresh water through it to flush more out? Do you run the engine at that point or just let gravity take over? Once flushed and drain plugs are reinstalled - the manual says to fill resivour with water and fill to the line the recovery tank with coolant. Am I just over thinking this? Drain it. Flush it. refill tank and recovery tank with coolant. Replace cap. run engine and bleed as per above?

 

[Ron20324]

I’ve tried to remove the coolant drain plug on the rubber coolant hose but it won’t come out. I’m able to turn it counterclock many times but it doesn’t want to come out all the way. Any suggestions? thanks, Paul

That looks like a crimp-on clamp.