Diesel Rated Coolant?

Rick D

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Jun 14, 2008
7,132
Hunter Legend 40.5 Shoreline Marina Long Beach CA
I am due to change out my coolant on my Yanmar 4JH2E on my 1994 Hunter 40.5. Hunter installed the green anti freeze on her and last time I changed it, I did the same. However, I have been reading that diesels should have diesel-rated coolant. The several auto parts guys I asked had no useful information. Google-searching, the info seems to imply that diesel rated coolant is (only) necessary with wet-liner engines. I don't believe my Yanmar is a wet-lined engine.
Anyone on the forum have a clue? It's a PITA to change out the coolant, so I want to do it right.
Edit to add: it's a dry-sleeve engine.
 
Last edited:
Feb 10, 2004
3,919
Hunter 40.5 Warwick, RI
I never heard of Diesel-rated coolant. But I have been accused of living under a rock.
What does Yanmar recommend?
If there is such a thing as diesel-rated coolant, I would like to understand why it is special and why it is necessary.
I will stay tuned.....
 

ToddS

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Sep 11, 2017
248
Beneteau 373 Cape Cod
I'm also eager to hear where this conversation goes. My newish-to-me boat has a yanmar y3m30 and coolant was newly changed when I bought the boat about a year ago. I wasn't planning to change mine this year, but in replacing a water heater, I drained/spilled quite a bit of my coolant, and I'm wondering if I should use this as an opportunity to switch to the long-life orange stuff (which might match up with what you're calling "diesel rated"). From poking around the interwebs, it would seem that Yanmar may have changed their recommendation over time...
 

Rick D

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Jun 14, 2008
7,132
Hunter Legend 40.5 Shoreline Marina Long Beach CA
I forgot about that other thread. Thanks for pointing it out. It appears that even though the cylinder liners are not wet, they are thin enough that cavitation may be an issue. Unfortunately, it also appears either a regularly-tested mix and use of an additive or a long life formulation is required. The long life formulation requires a full flush which I was seriously not looking forward to doing, but looks like it's in the cards. Of course, she's had the green stuff in there for 2800 hours and 24 years, so I guess the argument can be made that if it isn't a problem by now, it's not likely to be one. Still I do want to do it properly. I'm going to do some research to see if there are any universal formulas that make a flush less of an issue, but I suspect not. Here is a link to a Shell discussion of their products and a motorhome discussion on the same issue:
https://rotella.shell.com/en_us/products/lubricants-heavy-duty-products/antifreeze-coolant.html
http://www.motorhome.com/tech/diy/what-you-need-to-know-about-diesel-antifreeze-and-coolants/
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
The wet liner cavitation problem is not an issue with Yanmars because the coolant does not touch the liner, it only touches the block walls which are much thicker.
 
Oct 1, 2007
1,856
Boston Whaler Super Sport Pt. Judith
I use the Yanmar brand coolant and change it every other year, as recommended.
 

NYSail

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Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
Shell rotella elc is what I have been using in past yanmar 3HM35f and now my 4JH4E. Came highly recommended from yanmar tech. Make sure you first do an extremely good flush of system to gel all old residue out prior to adding.

Greg
 

Bob S

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Sep 27, 2007
1,771
Beneteau 393 New Bedford, MA
I just finished changing out my coolant with NAPA Extended Life (I had two gallons on hand). I also ordered 6 Gal of Fleetguard ES Compleat OAT for the next few changes. I'm not sure how diligent the previous owner was but I plan on doing this annually. I have the 4JH3E and the job wasn't as easy as I thought it would be. My arms are gonna be bruised. The 393 steps don't raise quite high enough to give good access. After draining I flushed the system out with distilled water and drained again. I removed the HW heater hose at the thermostat and used a shop vac to blow the lines out. I used a funnel to add fresh coolant to those lines and reattached them. I put a gallon + through the fill cap but it is too high to see into. i used a mirror to try to see if I used enough coolant. I ran the engine for 15 minutes on the hard and got her up to 160° with the cap off.
Stupid question... A Google search says 6L plus I assume whatever the HW heater line will take. How do you know when you've added enough (Full) or too much or not enough?
 

ToddS

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Sep 11, 2017
248
Beneteau 373 Cape Cod
I have a question that is a bit of a tangent, but also not entirely unrelated... my apology in advance if this seems like it is hijacking the topic. I just replaced my hot water heater (with a coolant/heat exchange to warm the water). In the process of disconnecting the old heater, and installing the new, I lost a fair amount of coolant (in the old heater, in the lines, etc.). I haven't started the engine yet (boat is being launched tomorrow), but obviously I anticipate I'll need to add coolant to replace what was lost (maybe a quart or two), and somehow bleed out air from the system. After doing the swap the other day, I opened the coolant fill cap on top of my engine (Yanmar 3ym30) to see how low the coolant was, and it appears to be totally full. The water heater is physically lower than the coolant fill, so obviously there's more than just gravity at work here (otherwise coolant would have drained entirely out of the water heater hoses while detached). Does the engine's thermostat control coolant flowing to the water heater loop? Assuming yes, do I need to run the engine long enough to get that to "open", and then add fluid, as the level falls in the coolant tank? I can't bleed the coolant loop if nothing's flowing into it... and I know these might seem like "rookie questions", but... can I add coolant to the overflow bottle to more easily "see" the coolant level while I'm running the engine to get coolant out of the coolant fill tank, and into the water heater, or do I need to add/monitor through the actual fill cap on top of my engine (not as easy to access/see especially while the engine is running. Not that it really matters, but I'm using Ethylene Glycol (green stuff) that's only seen one season of light use, so I'm not planning on flushing the system and starting fresh if I don't have to... planning on just topping off with more of the same (E.G.). Thanks for any advice/tips/clarification in advance.
 
Feb 10, 2004
3,919
Hunter 40.5 Warwick, RI
On my system, a Volvo MD22L-B, the engine will automatically bleed air in the system and suck in coolant from the over-flow tank. This may take several cold to hot cycles to complete. After the first cycle and if the coolant tank is empty, I would open the pressure cap (when cold) and add any coolant necessary to bring up to level. Then replace the pressure cap and add coolant to the over-flow tank. I think that will be all that is necessary. But still monitor the level in the over-flow tank over the next few cold-hot cycles.
 
Mar 26, 2011
3,401
Corsair F-24 MK I Deale, MD
(I spent 20 years developing new formulas, formulating coolants, and manufacturing glycol.)

a. Long-life does not mean much in a boat, since the common recommendation is to change it every 1-2 years due to the risk of seawater contamination due to cooler leaks. It only takes 20-50 ppm chloride to knock it out of spec, and seawater is 23,000 ppm. Don't wait 5 years, no matter how low your hours.
b. Diesels using wet sleeve liners can be prone to cavitation pitting if run at high load factors. This is why there is an ASTM HD coolant spec (D 6210). Non-sleeve engines are less susceptible, but are NOT immune. Many are now recommending OAT (like Dexcool) coolants, because although not HD, they good enough against pitting for non-liner engines and because they are widely available. Of course, always read the manual, since there may be engine-specific factors.

The cavitation is caused by piston slap on the cylinder wall during the down stroke.
 
Jul 26, 2015
42
Watkins 29 Ft. Lauderdale
I've been using Peak 50/50 in my 2GM20....as did the previous owner for 20 some years...we are in Florida so freezing isn't an issue but cooloing and lubication is!
Peak 50/50 is readily available to buy, compatible with all other types of coolant and relatively inexpensive!
 
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senang

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Oct 21, 2009
304
hunter 38 Monaco
These are my notes, found them somewhere on the net:
Yanmar accepts the following antifreeze applications in their products, present
and past models:
1. Ethylene glycol-Changed annually regardless of hours of operation.
2. Extended Life Antifreeze or Coolant (Meets or exceeds ASTM D3306 & D4985)
Changed every two years or 250 hours whichever comes first.
-Yanmar Ultralife YG30
-Dex-Cool Long Lfe Coolant
-Havoline Extended Life Antifreeze
Benefits of extended life coolants:
1. reduces hard scale build up
2. better heat transfer
3. no phosphate or silicate formation
4. long term corrosion protection for aluminum, bronze and cast iron
5. improved water pump life