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Old 10-05-2016, 10:18 AM   #1
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Dex Cool Blues

Coolant was a bit low in Tonawanda so I sent a crew member to NAPA for some anti-freeze. We had just poured it in when another crew member said he had heard of problems with the Dex Cool we just put in. Some Internet research and a call to NAPA revealed that, yes, it was a big problem. The NAPA guy said he just topped up the coolant in his truck with the stuff and ended up with balls of jelly that nearly ruined his engine.

Another call to the Perkins expert brought back the opinion that, ANYTIME, a new coolant is introduced, the engine should be flushed and you should always use the same type. Amazing the holes in your knowledge that can exist after a lifetime around boats. I never new that anti-freeze was so ticklish. Of course, most of my cruising has been with a RW cooled engine.

It turned out to be a fortuitous mistake which made my crew member feel better. Draining the engine revealed that we might have been the first owners to do so. Ugly. One of the block drains was solidly plugged. We picked and stuck in wires for a couple of hours to no avail. I went to the hardware store and made up an adapter to put street water pressure on it backwards. NADA. We left the hose inflated and the water turned off overnight. It still had full pressure in the morning but, with a bit more wire probing, the engine drained.

We then re-filled with plain vanilla anti-freeze recommended by NAPA for diesel engines.

Anyone else had problems with Dex Cool?
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Old 10-05-2016, 11:47 AM   #2
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I have read about similar problems with mixing different types of antifreeze.


But don't damn Dex-Cool. It is absolutely essential for Yanmar engines with aluminum exhaust manifolds to prevent cavitation corrosion.


But all others can use the more traditional green antifreeze.


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Old 10-05-2016, 12:46 PM   #3
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If you don't know what coolant is in your engine, don't mix. Just top up with dist water.

If you top up often, fix the leak.

If you don't know what is in there, it could be a mix. At next maintenance, drain, flush well, and then load it with what the engine maker recommends.

Engines with lots of aluminum like Yanmar and Volvo, some Perkins and some Lehmans- follow the coolant maintenance specs very carefully.

Also if engines have wet cylinder liners- do as you are told!! Liner pinholes are no fun.

Engines with no Al and no wet liners: Cat 3208, B Cummins, DD 71's, etc, they are not terribly picky. But don't mix, that can create goo.
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Old 10-05-2016, 12:57 PM   #4
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I hate DEXCOOL. From what I read, you can not have any air in the cooling system or it turns to jelly, etc....also cant mix with the green stuff, again turns into jelly.

Really there is no point to using it, and a lot of negatives, ethylene glycol works great.

How about Evans permanent antifreeze?

Watching the guy says it increases diesel engine efficiency 3 to 8% since it runs hotter?
Might be worth it for lowering maintenance, so what are the negatives besides the price?
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Old 10-05-2016, 01:35 PM   #5
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"Runs hotter, so efficiency is better." Let's debunk that statement.

An engine only runs hotter if the thermostat is wide open and it is no longer regulating temperature. This happens at high power loadings normally. More heat means that the temperature climbs and with the higher temperature, there is more heat transfer which cools it off until it reaches an equilibrium temperature.


But this antifreeze has a lower heat transfer coefficient- less heat is transferred at the same temp. So instead of temps rising to 190 at wot asvfor most engines, with this antifreeze the temp will rise to what 200,210,....? That gives you not much margin of safety if you loose an impeller.


Then the theory goes that at the higher engine temps it will be more efficient. Well true, but no where near 8%. Maybe 2-3%.


And you can accomplish the same thing by filling your coolant system with 75/25% or even 100% antifreeze solution. Pure ethylene glycol has a lower heat transfer coefficient than water.


But I don't recommend using this stuff or 100% ethylene glycol either. I want the maximum heat transfer consistent with freeze protection. When I boated in the Galveston Bay area, I ran 25% glycol 75% water for more heat transfer as I didn't need much freeze protection.


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Old 10-05-2016, 02:26 PM   #6
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If your engine could run 30-50 * warmer than 180*, would this be a bad thing?
If your running using a full synthetic oil, the oil can handle getting warmer.

Now this might be a bad thing in a gas motor, it could ping preignition, etc.. melting the pistons.
A diesel is built tougher, so why would a hotter running diesel burn up it's pistons?
I have seen pictures of burnt diesel pistons, why did they fail? Thermal runaway due to cooling system failures, bad oil, injectors to big, too much boost?
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Old 10-05-2016, 02:38 PM   #7
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Follow the manufacturer's instructions. I'm familiar with Volvo's. Volvo sells two very different coolant. Green and orange. The color is not important but the chemical composition is. They cannot be mixed and you can never flush an engine well enough to switch from the green (older formulation) to the orange.


Some engine manufacturers are not as picky as Volvo but if you want to prolong your engine's life and eliminate coolant caused issues, find out what the manufacturer specifies and us this and only this. Carry spare coolant so you don't have to settle for something that may not be compatible.


Yes, you can save a few dollars, but that engine might cost $25K or more. Want to risk it?
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Old 10-05-2016, 02:51 PM   #8
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Article on Evans coolant for managers of diesels in fleets.
Primarily PG not EG.
With water based coolant, a problem is boiling, turning into vapor against cylinder walls
Which waterless coolant does not do, so less chance of damage from overheating.

Waterless vs traditional coolants| Public Works Magazine | Heavy Equipment, Evans Cooling Systems Inc., Auburn University‚€™s PAVE Research Center
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Old 10-05-2016, 04:50 PM   #9
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In certain high heat flux regions, boiling can actually be an advantage. The bubbles create turbulence and also bubble formation removes a lot of heat and moves it elsewhere. The process is called 'nucleate boiling" and the heat transfer associated with it is well understood.

If you use a coolant that will not boil, you lose the advantage of NB heat transfer.

In extreme cases, you get film boiling and heat transfer drops to near zero, not good. Not a concern on a healthy engine.

I would not use a coolant that is not recommended by the engine mfr. They know what the heat transfer mechanisms are in various places and what they spec should work.

I would not use Evans unless the engine was designed for it.
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Old 10-05-2016, 05:20 PM   #10
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Now you have me worried. Just topped up my Westerbeke 5.0 BCDB generator's expansion tank (which was empty due to broken tubing between it and the gen engine) with the Fleetguard anti freeze my boatyard says to use in my Cummins 6BTA. The container says "compatible with all coolants". Was not the same as whatever was in there before. Have not run the genny yet since doing this. Potential problem?
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Old 10-05-2016, 06:07 PM   #11
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It seems a lot of people are confused by the different types of coolant.

There are 3 main types.

1.Traditional

2. Organic Acid Technology (OAT)

3. Hybrid Organic Acid Technology (HOAT)

Mixing rules
#1 and #2 cannot be mixed.
#3 can be added to either.
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Old 10-05-2016, 06:19 PM   #12
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Quote:
Originally Posted by dwhatty View Post
Now you have me worried. Just topped up my Westerbeke 5.0 BCDB generator's expansion tank (which was empty due to broken tubing between it and the gen engine) with the Fleetguard anti freeze my boatyard says to use in my Cummins 6BTA. The container says "compatible with all coolants". Was not the same as whatever was in there before. Have not run the genny yet since doing this. Potential problem?
If you just poured in the plastic recovery bottle, and did not run it, it probably did not mix. Just drain the plastic bottle and put in what the gennie has.

Or just drain and flush it and then use the fleetguard in both machines.
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Old 10-05-2016, 06:49 PM   #13
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Quote:
Originally Posted by dwhatty View Post
Now you have me worried. Just topped up my Westerbeke 5.0 BCDB generator's expansion tank (which was empty due to broken tubing between it and the gen engine) with the Fleetguard anti freeze my boatyard says to use in my Cummins 6BTA. The container says "compatible with all coolants". Was not the same as whatever was in there before. Have not run the genny yet since doing this. Potential problem?
Fleetguard makes all 3 types of coolant. If it says "compatible with all coolants", it would be the Hybrid Organic Acid type.
Fleetcool EX and ES Compleat are both in this category.

Go ahead and mix with any other type.
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Old 10-05-2016, 08:10 PM   #14
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When I bought my boat the starboard engine overheated when run more than 30 minutes. It took that long because it has a loop to the water heater. Anyway, in trouble shooting I found big blobs of crystalline jelly in the header tank to heat exchanger passages. I cleaned and flushed all this stuff out and now the engine runs cool. (Perkins 4-236. I later talked to the previous owners son and he had suggested to his dad he use DexCool because it was "long life" good stuff. Well, I do not recommend this stuff for old school diesel cooling systems. It will jelly up and plug your system.

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Old 10-05-2016, 08:52 PM   #15
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Dex Cool was one of the Yanmar recommend coolants. I couldn't find the other coolants so I used DexCool. I flushed the old coolant out before adding. Hope I don't have jelly.
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Old 10-14-2016, 09:29 PM   #16
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thank you

Thank you for posting about DEX COOLANT...
I read it one day after I changed the antifreeze in both of my diesel engines and replaced perfectly good green antifreeze with orange dex....
25 flushes later (50 counting both engines) I was able to remove any hint of orange and replace the Dex with another Prestone product...one that is good with any color coolant....
I hate to think what would have happened if the DEX had sat in my engines for the 6 months that we leave our boat.
Thank you for the original post!!!!!!!!!!!!!!!!!!!!!!!!
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Old 10-14-2016, 10:08 PM   #17
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Changed the coolant in my charter boat before laying it up for 18 months. Think I have <$50 in antifreeze, distilled water and Napa Cool for 7+ gallons. Do it at least every other year. Have never understood why people are so resistant to changing this stuff regularly when you consider how minimal the cost and how critically important it is.

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Old 10-14-2016, 10:50 PM   #18
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Yup diesel rated antifreeze, distilled water and DCA additive which my engine needs.
Done at 2 year intervals.

I think some people just think antifreeze is forever. Isn;t the car; actually no?

Some engines though are a pain to change and then purge air afterwards. It takes some willingness to make some minor changes to ease the work and reduce or eliminate the mess. My first time with this boat was a mess so I added valves and hoses and no more mess unless I get plain dumb clumsy.

I do remember one time getting some of that jelly. I never did really figure out why since I had done several changes after getting the boat and I always bought the same stuff so there was no mixing. I still buy the same stuff but no more of that jelly in the many years since. A goofy batch?
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Old 10-15-2016, 11:49 PM   #19
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My Hinos have aluminium manicoolers I change the antifreeze every 2 years with a 50/50 mix with distilled water. I use the Peak brand of green antifreeze, I just bought coolant test strips to test the ph and may start using that as a guide to changing coolant. The coolant in them was fresh this spring and has 214 hours on it now.
A contractor I worked for 30+ years ago used DowTherm coolant, it is alcohol based and leaves the cooling system components very clean. If a leak develops into the lubricant it mixes with the oil and will not harm the bearing inserts, the bad is if a external leak sprays on a hot turbo it will burn.
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