SailNet Community

SailNet Community (
-   Gear & Maintenance (
-   -   Coolant Question (

labatt 07-20-2007 01:25 PM

Coolant Question
We've got a Yanmar 4JH3E. We just noticed that the external coolant tank is EMPTY so we're assuming we have to bring it up to the fill level. Since the boat is new to us, is it recommended to do a full replacement of the coolant before adding new coolant? Or can we just buy any marine coolant (what kind do we get?) and fill 'er up to the full line? If we need to do a replacement, is there usually a coolant drain screw?

Cruisingdad 07-20-2007 03:22 PM

Hi Labatt,

I am not a diesel mechanic, so I will tell you what I do...

Regarding the overflow, assuming that is what you are talking about, yes, fill it up to the cold line. Your mixture should be 50:50 antifreeze and water. Also, with the engine cold, check the "radiator cap" and make sure she is full. I use automotive type antifreeze/coolant.

I would just add new coolant unless the old needed replacement. One word of warning that I have been exposed to: Often times when changing out the fluid, especially if flushing it clean, you will expose any pin holes. Watch for leaks if you do flush it. I am not sure why that happens, unless the flush cleans out the lines/rust that clogged the holes in teh first place.

One other question: Where did the fluid go?

Again, these are what I would do. If someone more knowledgeable knows better, please feel free to correct me.

- CD

redcorvette1995 07-20-2007 03:39 PM


Do not use just any automotive coolant. Lookup the specs for your engine and use the recommended coolant (yanmar will typically recommend 2 or 3 approved types). It will almost certainly still be a type of automotive coolant, but it will be speced for the engine. This is important as different coolants are compatible with different materials in the engine. If you get the wrong coolant it can be disasterous. Since the boat is new to you and you are not sure what coolant was used, I would drain and fill it. It won't cost you any more money as you have to buy a full jug of antifreeze anyway. If you don't mind spending a few dollars more mix the antifreeze with distilled water as this eliminates the impurities and minerals.



sailortjk1 07-20-2007 03:43 PM

I have been watching this and waiting for some responses.

We had an overheating problem this spring.
Same situation, resevoir was empty.
I added a 50:50 mixture right off the shelf.

Still had an overheating problem.
Contacted my yard, and they said that I used the wrong stuff..???
They corrected it, and I have not had a problem since than.

Cruisingdad 07-20-2007 04:47 PM


What wrong stuff? WHat did they do different? I agree about the spec on the antifreeze stated by corvette (I think Prestone works on the 3E)... but what differences did they do?

- CD

sailortjk1 07-20-2007 04:52 PM

I wish I knew.
(I didn't ask)
Sorry Dad, I wish I had been more deligent.
I just kinda let it go after that.
One thing though, they did not charge me for that one.
Said it was too stupid to charge me for it.!!

danjarch 07-20-2007 05:12 PM

Did you bleed out the air in the engine? You should have bleed screws on the top of the intake manifold and near the upper water inlet. You open these up until a little water comes out. If you leaked or overflowed enough coolant to introduce air into the system, it could have had trouble getting all the air back out by itself.

Cruisingdad 07-20-2007 05:14 PM


Originally Posted by sailortjk1 (Post 169553)
I wish I knew.
(I didn't ask)
Sorry Dad, I wish I had been more deligent.
I just kinda let it go after that.
One thing though, they did not charge me for that one.
Said it was too stupid to charge me for it.!!

That is interesting. Please let me know if I have been doing it wrong all these years. I sure don't mind admitting my mistakes (though I did preface this with I am not an marine engine mechanic!!!)... but my engine has never run hot. You sure you weren't using Koolaid in there?? (smile).

- CD

labatt 07-20-2007 05:22 PM

Does anyone know what the approved coolant types are for this engine? The PO didn't leave a manual so I'll need to order one. Also, any clue on the proper procedure to drain this type of engine? I'm going to start poking around looking for a drain plug/screw, but if there isn't one and I'm supposed to be siphoning or using a pump through the radiator cap... that would be handy information :)

Valiente 07-20-2007 05:29 PM

I just had this problem. It was a slowly leaking "rad" cap atop the heat exchanger. It was rated at 14 PSI: I got the same sized one for nine bucks at an auto parts store rated at 16 PSI. I'm glad I did (see below).

I use green "diesel coolant" at 100% strength. I must be doing something right, because my V-belt snapped when I was puttering to and from the poop dock, I didn't notice and the non-circulating coolant got to 230 F without boiling over or otherwise exploding.

But I sure as hell now know why they call it an "expansion" tank.

There are drain plugs usually on the front of the heat exchanger and/or at low points on the block in the cooling circuit. I have the shop manual for my engine (Westerbeke W-52) and I must say I refer to the thing about twice a month just to get used to all the extra crap on a bigger diesel when compared to an Atomic's a hell of a lot more engine.

All times are GMT -4. The time now is 11:06 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
(c) LLC 2000-2012

For the best viewing experience please update your browser to Google Chrome