3JH4E coolant change (new owner)

[fatsailor]

First time poster - be gentle.

I’ve a new to me 3JH4E, and I want to remove the current coolant and flush it as I have no idea the coolant used by the previous owner.

I’ve two questions:

1. What is the contraption in this picture- an air bleeder? It’s connected to one of the hoses going to hot water heater. I suspect it’s to help bleed off the air when refilling with new coolant to prevent an air lock.

2. The second picture is from the manual and it appears to show 3 coolant drain cocks? I was expecting only 2 and want to confirm there is a third on the opposite side of the other two. That area of the engine is super hard to get access.

Thanks!

[Nicholson58]

First picture. Is that a service port to easily enable flushing and running from a hose While on the hard?

As difficult as it is, you need to map the flow paths.

[fatsailor]

The hose is on the coolant line not the sea water line. It’s either the return or feeder to the hot water heater.

I’m pretty certain it is to bleed air from the coolant circuit. I’m just not clear on how best to use it. My previous boat didn’t have one of these.

[kaisardog]

if you can get a copy of the yan 3JH4E service manual, it has a piping diagram that shows fluid flows. (mine did not have the bleed valve on the supply line to the hot water heater. your water heater manual may have some suggestions on why that valve was installed. my nauticat 321 w/ isotemp hot water heater and 3JH4E didn't have one. ) suggestion : if you are going to change the coolant just as a precautionary measure , run a coolant flush which is an additive put in to the 'freshwater' system aka radiator. plan to change your thermostat and its gasket, and pull and clean the heat exchanger at the same time. (if you pull the heat exchanger, you'll need the special yanmar heat exchanger end cap gaskets , as form-a-gasket is a poor substitute for the good OEM gaskets ones. then fill with good quality Delco , yanmars are particular about what antifreeze to use in their 'freshwater' systems.all that being said if your engine is running at normal operating temps and is not losing coolant, i'm not sure i'd bother w all the above work til it's necessary...

[sailormed]

I just did a complete coolant refill and HE cleaning on my 3JH4E after replacing the hot water tank one month ago.
There are 4 drain cocks on this engine. On port side 2 cocks aft of the engine, one coolant one seawater. On SB aft 1 coolant drain, this is the major one.

The last coolant drain is on the front under the water pump behind the stupid cover.
The best way to empty the hot water tank is to take off both hoses going to the hot water tank and place one hose close to the boat bottom. Mark the hoses so you put them back in place. The hose with the air purge cover (lower) is the return line.

I filled the water heater loop before putting the hoses back on the engine. For purging the WH loop try to pull on the hose to put the purging cover as the highest point in the coolant system.

[hlev00]

One note on coolant type. Yanmar coolant is a red type that is for alloy compatibility. My 4JH4E is in a Beneteau and for some reason Beneteau commissions the engines with yellow/green type. On my first flush after buying the boat used, I switched it over to Yanmar red type. If you don't have red coolant and you can get a good flush, this would be a good time to change over, of course after verifying the type recommended by Yanmar for a 3JH4E. Just don't mix coolant types.

harry

[Kd9truck]

Originally Posted by hlev00

One note on coolant type. Yanmar coolant is a red type that is for alloy compatibility. My 4JH4E is in a Beneteau and for some reason Beneteau commissions the engines with yellow/green type. On my first flush after buying the boat used, I switched it over to Yanmar red type. If you don't have red coolant and you can get a good flush, this would be a good time to change over, of course after verifying the type recommended by Yanmar for a 3JH4E. Just don't mix coolant types.

harry

I second This suggestion, I took a Yanmar small engines owners class last fall and the instructor (35nyrs fixing Yanmars ) stated that the coolant mix Is formulated specifically for there zinc-less motors and that if you don’t use the proper coolant there will be electrolysis. Many would and May argue this point, I am just communicating what I heard, post away I will not respond.
And an even more controversial point, the red coolant is also compliant with marine conservation guidelines, I have herd from several Coast Guard friends that should they board your vessel and you do not have marine diesel (red) they will check the anti-freeze and you will get a ticket if it is green/yellow as these are not marine environment formulated.
Not my rules just what I was told and I have no reason to believe there was a conspiracy to lie to me.

Good on ya!! Getting in there and getting that done, cheers

[kenbo]

No need to buy Yanmar coolant, they just repackage a major manufacture's. I have always used Shell Rotella ELC coolant. Oh and it's red and aluminum friendly.

[fatsailor]

Thanks @kenbo - I was planning on using Rotella ELC NF as well. It was hard to find though.

I guess I’ll ask the dealer’s service department who originally sold the boat new how to use that bleeder correctly.

@Sailormed - thanks as well. I’m going to put off the HE until next coolant change. That’s a bit too much to handle right now. The current bleeder valve is at the high point in the system. If it’s automatic, I don’t need to worry about anything. But, I suspect it is manual so I’ll have to figure out how to use that the best way.

[Midnight Son]

I do not know of a Diesel rated coolant, that is not aluminum compatible. Some engines also have copper injector cups, to add to the electrolysis fun.
Larger engines have coolant filters with a chemical pack to stabilize the coolant for a year, thus allowing the coolant to be used for multiple years, filters to be changed annually.
Small Diesel engines, should have the coolant replaced annually, flushed if sediment is detected (after checking for electrical current flows in the engine, as sediment is possible result of electrolysis, consult service techs in that case).