Dex-Cool : What Color Does It Turn if Bad?

[rardiH36]

If the anti-freeze is Dex-Cool, are there any indications of problems before damage is noticed --- such as the coolant turning black?

I ask because before the first outing after I bought my boat (1.5 years ago), I drained (but didn't flush) the coolant, then added new anti-freeze (lime-green Prestone). After returning to the dock after my first day, I noticed that the coolant was jet black. I drained again. In the container, the black precipated to the bottom after a couple of hours leaving the upper section of the liquid pristine looking lime-green. After refilling with clean anti-freeze, the coolant turned black again almost immediately.

At the time, I posted the question on this site and got some good responses. Several suggested blow-by of exhaust past the head gasket into the coolant. Another said it could be the type of coolant (GM). Other than the black, the engine was performing wonderfully, and because a blown head gasket is something I wanted to wish away, I first focused on the coolant.

Anyway, it took quite a few flushes over several days of motoring to finally clear out all of the blackness. I've replaced with an extended life coolant. Now I've gone 11-12 months and the coolant is still lime-green (yes it's time to drain and replace again). The engine still works just fine, so seems that the head gasket is OK. Hope if was Dex-Cool, I got rid of it before any deep damage.

MaineSail, thanks for starting the thread on heat exchangers. When I bought my boat, the heat exchanger had some pin-hole leaks. A local radiator shop fixed it up almost like new (albeit for more $'s than you paid -- but I live in a San Francisco area county where repair shops price for owners of BMW's, Mercedes, Porsches, Lexus's, Jaguars etc which seem to outnumber Fords/Chevy's by a good margin). I'm replacing the heat exchanger's seawater side zinc frequently. I am surprised at how fast it is depletes.

 

[alanwir]

Your observation about Dex-Cool brings to light some very interesting needed review. YanMar has promoted long life anti freeze (pink) for some time and actually stressed using a very specific product (which I do not wish to name to avoid any legal complications). The reason, the pink product was suppose to be lower in silicate content and was less damaging to heat exchangers. Well, if you look for the YanMar suggested producer's anti freeze product(s) manufactured during the late 1998 to approixmately 2007 time frame, you more than likely will not find them on the US market any longer. There was a class action suit with Long Life Anti-freeze because GM cars spec.ed for its use, seem to be undergoing corrosion on the engine walls carrying this anit freeze long life fluid. Appearently the suggested YanMar product long life manufacter also has an organic acid component in it which may or may not cause this corrosion-you are left to be the judge as the suit was settled with claims of no wrong doing (and maybe it is some other trace component in the formulation that was causing the problem). Bottom line, one could be left with less ware and tear on the heat exchanger as less silicates will keep from clogging the tiny holes in the heat exchanger that the fluid must pass through or be faced with now a possible corrosion situation.

Mixing products that are 2 years old or more (pink with green) causes a undesired precipitate to occur which happens fairly quickly and can render the cooling system to be totally non functional. This is the black you are seeing and if you are using older produced anti freeze, you are always instructed not to mix the 2 and when changing from pink to green you have been required to flush very carefully. In addition one is always instructed, no matter what product you have been using, to always use a 50-50 antifreeze blend and if you purchase a 100% product, you must cut it will distilled water, tap water should never be used. Ethlyene glycol cannot function as a 100% product-it needs the water for the proper heat exchange to occur.

If you look closer with some of the newer anti freeze on the market (production approximately 2008 and newer, you will find a product that is green in color which states that the product can be safely mixed with green or pink, these manufacturers must have used a formulation change which is not so readliy appearent on their labels

The best case scenerio would be that if you had been using a green anti freeze type all along, stick with it (even if it does contain silicates and phosphates) and change out with the green ethylene glycol older formulated 50-50% types. Of course this is how I read the situation, YanMar and other manufacters might have an updated response and if they do, I have not seen one yet and these are my observations, I do not wish to be sited as any kind of expert and offer the above as a guide to review and to ask addtional quesitons about the use of the various different formulations

 

[sailingdog]

Dex-Cool is bad stuff... you should replace it with regular antifreeze. IIRC, Maine Sail had a good post about the stuff and how bad it is for your engine a few weeks ago that you should probably read.

 

[Steve Dion]

I believe you will find that there is a problem mixing the older (green) product with the newer (pink/orange) extended life products. The mixture of these products can cause a gel.

We just had ours changed and the mechanic claims that there needs to be a complete flushing of the system prior to the refilling of the system with the new extended life product.

Our mechanic uses Shell products vs the Texaco/Havoline extended life products.

I know that there were issues on GM vechicles with head gaskets, but I do not know if this was more of a problem with the GM head gaskets vs the coolant. There does not appear to be much information when using the extended life product in marine engines when the system was properly prepared prior to refilling.

 

[Steve Dion]

Here is some more information. There is info from Yanmar (2002) that still recommends the extended life products, but you decide.

http://www.scyr.org/stellablue/coolant.html

 

[Maine Sail]

I know that there were issues on GM vechicles with head gaskets, but I do not know if this was more of a problem with the GM head gaskets vs the coolant. There does not appear to be much information when using the extended life product in marine engines when the system was properly prepared prior to refilling.

Don't forget the MASSIVE head gasket issues Suburu had with Dex-Cool. My mother had two complete head gasket jobs in less than 80k miles on the third they replaced the head gaskets and the Dex-Cool. The car now has about 140k and all is good... Oh and the head gaskets were not all that got eaten. Fortunately Suburu covered all this damage at their cost..

Just got back from the radiator shop and I'm glad I went. I got a whole lesson about why DEX-COOL is not a good idea. Unfortunately my 2003 Westerbeke came from the factory with DEX-COOL, and has been changed regularly, but it was not enough to prevent some rusty looking sludge in the HX fresh water side. Now I will also need to flush my engine and convert it to regular antifreeze. Sometimes newer is not always better..?

DEX-COOL Class Action (LINK)

DEX-COOL Class Action (LINK)

and more:

GM Owners Steaming Over Dex-Cool (LINK)

Dex-Cool.net (LINK)

San Carlos Radiator Specializing In Fixing Dex-Cool Issues (LINK)

I can say without a doubt that Dex-Cool will NOT last anywhere near the five years or 150k they claim it to as it certainly did not in my situation. It's really sad that Yanmar and Westerbeke are still sticking this stuff in their engines. I can't imagine what mine would be like had it not been changed regularly. My engine is a 2003 and it's been changed completely with fresh, brand name, Dex-Cool twice in five years and yet my motor still has the same rusty sludge experienced in cars.

 

[rpwillia]

Coolant Color and GM DexCool

I have a Saturn LS-2 (V-6) with 193K and have always used DexCool and have had no problems except for one heat exchanger that used silicone sealant (at about 160K miles) that leaked out onto the exhaust. Other than that no problems.

My first thought when hearing about the black stuff in the coolant was that it was probably radiator stop leak like Bahr's pellets. After your flushing you mentioned no more problems, but that there were some pin hole leaks in your heat exchanger. My guess is the previous owner tried to fix the leak with stop leak.

 

[Don S/V ILLusion]

I have used Texaco/Havoline extended life with no problems for many years. After doing some research on the reported problems, it appears the gasket issues blamed on the antifreeze may at least in part be from either overheating or insufficient fluid in the coolant reservoir or some combination. Regardless of the cause of the problems with dexcool, it seems a mistake to paint all extended life products with the same brush as there is ample evidence to show that low silicate type antifreeze is superior to the ubiquitous green stuff.

 

[DougM]

I think the GM Head gasket issue was more a problem with the type of gasket, than with the coolant. The stories I heard (all second hand) were that a cheaper gasket was spec'd because it saved about 50 cents per vehicle.

 

[Allan Frey]

The following is a recent response from Mack Boring:

Havoline extended life coolant (dex-cool) is fine for your Yanmar engine. It was one of the first coolants tested and approved for Yanmar engines.

 

[Maine Sail]

The following is a recent response from Mack Boring:

Havoline extended life coolant (dex-cool) is fine for your Yanmar engine. It was one of the first coolants tested and approved for Yanmar engines.

Alan,

I do not bring this up to tell you what you should do with your own engine. I bring it up in the hopes that some will do more research beyond what the engine manufacturers say to do. GM is still putting Dex-Cool in cars & trucks while at the same time paying out hundreds of millions in damages from the Dex-Cool suit.

Here is an interesting point to consider:

As long-lived as OAT-based antifreezes are, GM does not recommend using Dex-Cool in older vehicles with copper/brass radiators and high lead solder seams. The reason is that the additives in Dex-Cool can eat away at the solder, leading to premature radiator failure. There is also concern that it can erode water pump impellers that experience a lot of cavitations. (New GM engines have specially designed water pump impellers to minimize cavitations).

and this:

Can you run organic coolant in an earlier vehicle? Yes and no. OAT will work if your radiator is aluminum and you flush your entire cooling system with water and completely refill with OAT, but there are some issues with the interaction between organic coolants and lead solder, so using OAT in a copper radiator is not recommended.

Of course the makers of Dex-Cool insist it is safe for copper radiators & HX's...?? Who to believe is up to you guys..

Boats use copper heat exchangers which are generally soldered together with a tin/lead solder. Again I have done my own research, and know my own experience with Dex-Cool, I only post this as a beginning point for your own research..

If your own research leads you to a conclusion to stick with Dex-Cool that is all that matters as your own personal comfort surrounding your engine is paramount.

Some more reading:

ConsumerAffairs.com / Dex-Cool

 

[Big Windy]

The new DexCool in newer vehicles is fine. DexCool should not be used in older engines and should not be mixed with the green stuff. Rather than take a chance, I continue to use the green stuff in my Yanmar without problem.

 

[rardiH36]

Re: Coolant Color and GM DexCool

For rpwillia:

Re your observation (appreciated) that a PO might have used a stop-leak product also was a thought I had at the time of the problem; but had forgotten that I had thought of it. The Yanmar engine on my boat is a seawater cooled design that was retrofitted into a coolant cooled engine via a seawater/antifreeze heat exchanger that is mounted on a bulkhead. However, because of the retrofit, the thermostat on my engine opens/closes at 140 degrees F, compared to the normal ~170 F (or somewhere in that range -- I don't want to look it up right now) for engines initially designed for antifreeze/coolant systems. The lower coolant temperature is because (as explained to me by someone "in the know") about 140 F is about upper limit beyond which salt water will lay out all sorts of deposits in the coolant channels. I'm not a chemist, but expect that 140 F is too cool to activate any stop-leak properties of "stop-leak" products. So if a previous owner had tried to stop (or cover-up) problems with the heat exchanger, it was likely in vain.

Another "someone in the know" mentioned another possibility for black coolant. Because my engine was originally designed for salt water cooling, it has two zincs that are mounted into the engine block cooling circuit. Depending on the coolant, it may have reacted with the zinc. However, at the time of the advice, I looked at these zincs and they were not depleted at all and still had a clean grey color.

So, many possible causes of black coolant. But little certainty which it might have been. Anyway the coolant now is still green after one year -- and more than 70-80 outings ... The engine ran great even on today's sail.

rardi

 

[Steve Dion]

Have we ever heard from someone with a newer Yanmar that has ever had issues with this coolant? I think not.

I am still convincent that this is an issue with mixing non-compatible coolants.

Yanmar and many other mfg. are only using this coolant and are not replacing engines.

Does this make sense to you?

 

[Maine Sail]

I am still convincent that this is an issue with mixing non-compatible coolants.

Steve my 2003 Westerbeke has some rusty sludge issues and only ever had Dex-Cool used. It was never, ever mixed and it has been changed twice since new. This is what started this thread.... You never know until you look or have an issue.. My engine was currently cooling fine but was well on her way to not cooling well.

 

[RichH]

Black or a dark/blackish color in cooling water is symptomatic of a blown head gasket. Suggest you drain out a gallon of the coolant and take it to an automotive machine shop or precision rebuilder. That entity, if so equipped, can test the coolant with a special dye and 'black light' ... which will 'phosphoresce' if there is significant 'carbon monoxide' dissolved in the coolant -- indicates blown head gasket.
After running the engine 'hard' for a period, immediately drain the test sample, put it into a sealed container and take it to the shop ASAP.

So, when was the last time you re-torqued the cylinder head?

 

[tommays]

What do you guys make of the differance between RED(pink ?) dex-cool Vs ORANGE dex-cool

 

[rardiH36]

Hi RichH:

Presume that your head gasket/re-torque suggestion was in response to my post?

I had mentioned earlier in this thread (on Jan 15) that when I first found the black coolant after my first outing post-purchase 1.5 years ago, I put the question on this forum. A blown head gasket was one of the possibilities that members (maybe even you!) suggested to look at. Another (or others) said not to despair yet as it could be a type of coolant which might cause the black color. The local diesel service couldn't schedule a look-see within a reasonable time. So just wanting to do something, I decided to take off the valve cover for a peek, to check the head bolt torque, and to check the valve clearance adjustment while in the area. The first thing I noticed was that everything underneath the valve cover was spic-and-span clean. No dirt, sludge, even in crevices. Certainly too clean for 27 years of engine use. So, it occurred that maybe the engine had been rebuilt somewhere along the PO chain and then not used much. (I was told by the selling broker that each of the two PO's owned the boat for a couple of years, but never really used it. They did however put money into maintenance and upgrades.) If the engine had been rebuilt, maybe the head bolts weren't re-torqued after the specified hours. (I don't have my Yanmar manual at home, but 50 hours come to mind). In fact, I was able to tighten the head bolts some more to the specified torque. I'm generally handy, but not a professional mechanic. I would have thought the if the headbolt torque was insufficient and a breach occurred, then the gasket would have been damaged .... and just re-torquing wouldn't fix.

Anyway, whether it was the re-torquing, or that PO's had mixed wrong coolants, or the coolant hadn't been changed in several years; after multiple flushes of the cooling system, I've been black free for a year now. The engine runs fine. No smoke, no oil consumption, no water in the oil. Reaches the spec'd rpm. I haven't felt the need to call the diesel service again. Keeping my fingers crossed.

rardi

 

[Steve Dion]

Too many Yanmars running around with Dex-cool

Steve my 2003 Westerbeke has some rusty sludge issues and only ever had Dex-Cool used. It was never, ever mixed and it has been changed twice since new. This is what started this thread.... You never know until you look or have an issue.. My engine was currently cooling fine but was well on her way to not cooling well.

I think that there are too many Yanmars's running around with Dex-cool in their cooling system to say the stuff is no good. While there seems to be several sailors that have had these problems there may be a deeper seeded problem with the coolant.

GM is still using this product in the vehicles to my knowledge. It would be interesting to see if there is a cause/effect issue that has been covered up. I think most engine mfg. are using these products.

 

[sailingdog]

Steve—

Just because a lot of engines are using Dex-cool, doesn't necessarily mean they should be, or that the stuff is any good. There are a lot of people out there who don't know jack about engines or care about them, and farm out all their maintenance.