DexCool Coolant

A few rhetorical questions...

Was the coolant purchased prediluted 50/50% ?
Was the coolant purchased undiluted full strength and then diluted to 50/50% ?
If the dilution was done locally, what water was used?  Distilled or Tap Water?
If Tap Water was used, how "Hard " is the Local Water?

Heating "Hard" water will cause the dissolved minerals to precipitate out into "Rocks"
The Dye in the coolant will color the "Rocks" the same color.
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DexCool is foremost, a Brand of A/C Delco for their Organic Acid Technology Antifreeze.
It is a controversial product.  Google " Dex-Cool Lawsuits"  for more information.

Some variants of DexCool contain the additive " 2-EHA"  (2-EthylHexanoic Acid) 
This additive has been shown to attack Silicon-Based Heater Hoses.

DexCool may be fine for the Rotax AluminumEngine components.
The same can not be said of the remainder of the cooling system provided by the Airframe Manufacturer.

Hi group

I was involved with some of the original testing of DexCool in Rotax engines.  (582 and 912) Clearly if you have the DexCool forming a gel or solid it was not prediluted as it should be.  Any water added must be distilled water only and never tap water.  

DexCool is an OAT, Organic Acid Technology as Bill pointed out, as such it must be tested by the OEM on the OEM supplied parts.  We know that there is nothing within the supply scope of the Rotax engine that it will harm however other bits you can't be sure of.   The issue with some of the lawsuits stems from the incorrect use such as incorrect mixing.  GM users found that some parts within their engines would dissolve leaving a sludge of brown material that did a lot of damage.  (plastic in gaskets were hard hit) Even with that GM still sells its branded coolant with DexCool.  Any company that sells coolant if they label it DexCool it is from the original formula. 

Here is the good news.  It is good for 5 years (originally GM said forever but they were overly optimistic) Your Rotax has no internal plastic bits to dissolve in the cooling system, you do have to think about the OEM supplied parts to be sure) The aluminium parts will take on a dark grey appearance after running OAT and I have not seen any scale or buildups even after many years of running in any engines even after multiple TBO times have been reached.  GM still uses DexCool and changed a lot of the parts in their engines to solve the issues they had from the late 1990s and early 2000s.  Rotax also uses a ceramic water pump seal that has no issue with DexCool.  

For the most part most Rotax service people are told to recommend DexCool as the 5 year life matches the hose replacement times.  DexCool solved the repeated water pump seal issues that existed in the very early days of the liquid cooled engines.  it was not uncommon to fail a seal in 600 to 800 hours, normally now they go to TBO without any issue using the OAT compound.  

Cheers

I've been using Dex Cool 50/50 for the last 15+ years with all my clients and my own planes, autos and OHV vehicles and have never had a single issue. I think the original Dex Cool and some of its users had a few issues, but that should have been taken care of a long time ago. The orange Dex Cool is rated for 5 years on its label and fits right in with the 5 year rubber change.

Thanks guys, very informative.

I was considering using the Valvoline Zerex G48 since it is supposedly manufactured using the BASF Glysantin G-48 chemistry and which is approved by Rotax.

But given your feedback on the DexCool field experience I will probably stick with that. I do have silicon hoses from the cooler to the engine but after 100 hrs of use they seem fine. I don't like the dark grey color DexCool imparts on the aluminum parts but obviously it seems to cause no harm and stated here (thanks for mentioning that since that raised my eyebrows). I got my cooler that was heavily used in Europa and it was clean and shinny. oh well.

Best Regards,

Chris

Remember the Dex Cool of yesteryear is not the same as it is now days. The first time it came out it did have an issue or two with other coolants if someone mixed them. Plus it's still better not to mix and use distilled water