How to drain Antifreeze from Yanmar 3ym30.

Scott B · Jan 1, 2017

Check your manual, Pg. 35, Figures 8 & 10. I tried to upload a copy but too large.
Drain on the underside of the coolant hose and on engine block.

Neil Spooner · Jan 3, 2017

~Whilst you are on that job...it's well worth removing the front and rear covers of the heat exchanger and rodding through the heat exchanger to clear out any raw water sediment/scale build up. You will need two O rings and the rubber seal for the face of the tube block. It is also worth (if the boat is out of the water) to service the sea cock on the side of the sail drive, and possibly replace all the 5/8" hard wall water hose in the raw water circuit.....originally it is wire braced, the wire corrodes and the hose falls apart.
Also! Check the anode in the top of the sail drive leg...it gets forgotten.
Good luck,
Neil

Roland5048 · Jan 3, 2017

I have the 3YM20 in my boat. Yesterday, I attempted to change out the coolant. I say attempted because, although I removed about 3+ quarts, I could not get it all. Sucked as much as I could out of the heat exchanger with a vacuum pump and then let the rest flow out of the drain cock shown in the left diagram in post #3. Had to run the engine a bit to get the rest of the coolant flowing out. Had to wait for the thermostat to open first. At least I know that is OK. Did not overheat.
The diagram in my book labels the drain cock in the right diagram in post #3 as being a drain for the raw water in the block. Way too difficult to get at, anyway.
Coolant was still a clear pinkish red except for a little sludge in the reservoir. This is after 8 years and 560 hours. No lecture, please, on that. I know it was way overdue.
Doesn't seem, however, that I was able to put as much coolant back in as was taken out. Air block? Engine runs fine and does not overheat. Going back today and run it and see if she wants more coolant.
Besides taking off the hoses to purge any air that might be in there, is there an easier way? If, indeed, I do have an air block. Coolant flows just fine, however. Am I missing something here?
When I do this again, would a shop vac pressed up to the neck of the pressure cap suck enough out? This was one very messy job. There's gotta be an easier way.

Gunni · Jan 3, 2017

Roland5048 said:
The diagram in my book labels the drain cock in the right diagram in post #3 as being a drain for the raw water in the block.

There is no raw water in the block, only the HE. That petcock IS a coolant drain. There are generally three drains, plus the HW heater circuit. Yanmar's are easy to drain, get the proper size vinyl hose to fit the drain petcocks. Run the engine to warm the coolant and open the thermostat. Stop the engine, attach the drain hoses and route them to a jug or pan, open the petcocks. While you are draining take a hot water heater hose loose and blow into it (a dinghy pump works well), this forces coolant out of the HW heater and into the block where it can drain. After the coolant drains down a bit open the coolant cap to break any air lock and finish the drain. If the coolant is rusty and full of sediment flush the system with distilled water and run the engine to circulate. repeat until clear.

Roland5048 · Jan 3, 2017

Thank you, Gunni. I did like you said except blowing into the WH hose. Filled with distilled water, ran the engine, emptied, repeated. Coolant actually looked good but flushed until clear. I would need to be a contortionist or enlist a small child to actually get at the WH hoses, unless it is one of three that come around the front, and the petcock on the block. The WH and hoses were all replaced at the repower. Going back this afternoon and see what I find concerning the coolant level. If all is well, I might just let it be for now. Getting at least 3/4 or more of the original coolant out should be OK, I would think. Will report back. I'm afraid I might actually be over or under thinking this whole thing. It just can't be as difficult as it was.

Gunni · Jan 3, 2017

Your HW heater hoses should attach on the front of your engine, very near the fresh water pump and thermostat. That is the location to take one loose to blow out the HW heater. At the recommendation of Thinwater, a coolant expert, I switched to Cummins Diesel Propylene Glycol (ES Compleat PG) coolant. It is compatible with all coolants, so you don't need to be concerned by a complete flush, you just need to check the final coolant to make sure you have sufficient freeze protection.

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Roland5048 · Jan 4, 2017

Gunni said:
Your HW heater hoses should attach on the front of your engine, very near the fresh water pump and thermostat. That is the location to take one loose to blow out the HW heater. At the recommendation of Thinwater, a coolant expert, I switched to Cummins Diesel Propylene Glycol (ES Compleat PG) coolant. It is compatible with all coolants, so you don't need to be concerned by a complete flush, you just need to check the final coolant to make sure you have sufficient freeze protection.

Yes, the WH hoses are right where you stated they are. I would imagine the hotter of the two goes to the WH and that is the one to blow into. Or, does it matter? Ran the engine yesterday for awhile. Good flow, no overheating, coolant looks good. Going to let it be for now, unless a problem develops. Thanks for all your help.
BTW, went back to my manual yesterday and the drawing I have, just like the right one in post#3, labels the plug as the "drain cock for seawater". A misprint, maybe? Would have to wait until I change my oil to get to it, anyhow. What is it with these designers and engineers, anyway.
Caspurr, I didn't mean to hijack your thread. Just thought that while we had the same concerns might as well keep it simple.

Scott B · Jan 4, 2017

Roland5048 said:
BTW, went back to my manual yesterday and the drawing I have, just like the right one in post#3, labels the plug as the "drain cock for seawater". A misprint, maybe? Would have to wait until I change my oil to get to it, anyhow. What is it with these designers and engineers, anyway.

Seawater will only go through the heat exchanger to cool the freshwater. Seawater does not circulate through the block. The freshwater coolant is what circulates through the block and then the heat exchanger.

Funny, it took me a long time to get my head around "seawater" vs. "freshwater". Our boat is on the Great Lakes, which I consider "fresh" water. The coolant inside the engine I would consider anything but "fresh" from my automotive engine class days....

Roland5048 · Jan 5, 2017

Scott B said:
Seawater will only go through the heat exchanger to cool the freshwater. Seawater does not circulate through the block. The freshwater coolant is what circulates through the block and then the heat exchanger.

Funny, it took me a long time to get my head around "seawater" vs. "freshwater". Our boat is on the Great Lakes, which I consider "fresh" water. The coolant inside the engine I would consider anything but "fresh" from my automotive engine class days....

That was my understanding, also. And how did they know I was going to use it in salt water, anyway? I'll go through this again when I change my oil and get the filter off so I can access the plug.

Gunni · Jan 5, 2017

The Sea of Galilee is a lake. Just saying.

Yes, the hottest HW heater hose is the one coming off the engine. BTW, as noted by Thinwater, Ralph Johnstone and others we are supposed to be changing out coolant every year so it is good to come up with a quick and simple way of doing so.

Neil Spooner · Jan 6, 2017

Just a couple of thoughts:
Running the engine for an extended period with partial fill of coolant may find inadequate coolant to cool the upper part of the engine, particularly the cylinder head, which is the hottest part of the engine, damage to the cyl' head gasket is a definite possibility, so if you are going to do that make sure it is only for a minute or so, and avoid putting cold coolant into the engine immediately after.
You should find a bleed unit (plastic or metal in-line unit with a cap on the top of it) in the engine coolant circuit toward the top of the calorifier, on the H356 it is just behind it. You should find another in the cooling circuit close to the engine. With the engine running crack open the cap to allow any air out. Conversely when you drain down the coolant open these to allow the coolant to flow out via the drain valves.
The drain valves in the block frequently get blocked with sediment, so if there is no flow of coolant when opened remove the valve from the block and use a thin piece of wire to dislodge any detrius.
Flushing all the coolant out is rather OTT, not necessary, just make sure the correct level of antifreeze has been added. This provides the anti-freeze quality, but also corrosion inhibition, and increases the boiling point of the coolant.
The "radiator cap" has a one way valve built in to it, so as the engine cools any "air" in the top of the heat exchanger draws the coolant out of the small tank above the engine into the header tank. Therefore always check the condition of the rubber gasket within the filler cap at its top. If this is damaged the "syphon" function will not work.
Hippo New Year,
Neil

carol palmer · Aug 21, 2017

Caspurr said:
Looking for information on how to replace my existing antifreeze in my 3YM30 Yanmar engine.
Is there an easy way to drain the existing antifreeze. Checked the manual several times and do not see reference to a drain plug.
Thanks,

Check for the drain on the hose leading away from the bottom of the heat exchanger and another on the cylinder block on the opposite side of the engine. Yanmar favours the long life type of antifreeze as the drain cleaning service suggest.

If you are uncertain about the type in the engine flushing with plain water. The long life and conventional types should not be mixed. Else drain from both drain points and refill with the recommended type. Ensure thorough flushing with plain water especially if the old comes out looking dirty or mucky. I would also suggest a flush with plain water. Follow local regulations for the safe disposal of toxic substances like the antifreeze. Keep them out of the reach of children, pets, and other animals, this being sweet.

Use the correct orange coolant as the 3YM30 heat exchanger will clog with silicates if you don’t, due to having a very fine capillary. Check with at any GM/Chevrolet dealer.

Flush out the exchanger and remove it first to remove any foreign objects like bits of impeller blades that restrict flow in the raw water circuit. Check for spigot corrosion at hose ends, clean up as well. Run a degassing cycle after the fill.

John T1594 · Aug 21, 2017

I have the 3GM30F engine on my boat and flushed and completely changed out the coolant when I bought the boat several years ago. It had the old style green coolant and after a thorough flush I replaced it with the long-life orange stuff as recommended by Yanmar. The job was so difficult and time consuming that I vowed not to do it again unless absolutely necessary. What I decided to do instead was to drain a quart of coolant from the heat exchanger at the end of each season using the pet-cock on the underside (the heat exchanger holds only about one quart anyway). I then add one quart of fresh coolant, diluted to 50% with distilled water through the radiator cap. This way, I theorize, I gradually replace the anti-rust/corrosion and other chemicals in the engine coolant without all of the fuss and bother. I also check the specific gravity and freeze point of the removed fluid to see that it is up to specs.

seadaddler · Aug 21, 2017

Don't forget to take the front round cap on the HE and check for anything,I do this ever so often
and have found grass and parts of impeller and used the old O ring no problem.
Nick

MitchM · Aug 21, 2017

Neil S. is very right about his reminder to replace old raw water hoses especially from seacock to pump and not just on yan mars. if the raw water hose is a double wall , the old inner hose can collapse and deprive the engine of proper cooling water flow at high rpms. sometimes the failure is intermittent and only happens at high RPM s so the over heat will drive you nuts trying to figure out the cause.