What coolant do I have?

[n74846]

As I bought a flying 12 I am uncertain of the coolant in the tank. It is a straw-amber color. I have been told it is not Dexcool and I should be using a red one, however some photos in either Vans or Rotax shows the same color coolant in their photos.

 

[HansLab]

Coolant

I guess you have Evans. It is used by Rotax for a more wide thermostatische spectrum than just water with an additive. Evans is NOT to be mixed with other liquids! And certenly not with water.... Buy via AirSpruce. New it's kinda yellow.

 

[Harvey rv12]

The coolant reservoir cap should have a label if it is Evans waterless coolant.
I had that in my -12 when I bought it, and it ran hot. I replaced it with dexcool, and cylinder & oil temps went down 30 deg.

 

[DHeal]

Since you do not know what kind of coolant you have in your 912, I suggest that you drain all of the existing coolant out and thoroughly flush the system. If it was EVANs, I recall that there is a procedure suggested to totally purge the EVANs from the system -- you do not want to mix EVANs and water.

Apparently, ROTAX has removed EVANs from it's list of approved coolants -- particularly for engines with the new cylinder head design. Everything I have seen including the RV-12 Maintenance Manual suggests Prestone Dex-Cool 50/50 coolant (pink in color) which is what I use in my 912.

 

[n74846]

Thanks for the clarification and recommendations. I'm due for a 100 hour engine service and will have it changed professionally at Lockwood.

 

[RX Aviation]

I agree that it sounds like you have Evan's coolant. I would suggest you replace it with Dexcool. In my experience RV-12s tend to run at higher temps because of the tight cowling. Running Evan's coolant will cause your engine to run about 20-25 degrees hotter. Evan's is good stuff, but I wouldn't run it in an installation that already has known issues with higher running temps.

Hope that helps

 

[rvbuilder2002]

Evan's is good stuff, but I wouldn't run it in an installation that already has known issues with higher running temps.

That's interesting since my understanding was that Evans was originally adopted for use in Rotax powered airplanes that did run on the hot side because of its higher boiling point compared to traditional coolant (provided more safety margin if you often run near the temp limit).

It has since been found to be of little value because the poorer heat dissipation performance eats up most all of the boiling point delta since it will automatically cause the coolant temp to be higher just by using it.

I believe this is the reason that Rotax no longer recommends it.

 

[n74846]

As a post=script to my 100 hour engine service, it was determined that the unknown coolant is a water based product, but still unidentifiable by color.

 

[BillL]

That's interesting since my understanding was that Evans was originally adopted for use in Rotax powered airplanes that did run on the hot side because of its higher boiling point compared to traditional coolant (provided more safety margin if you often run near the temp limit).

It has since been found to be of little value because the poorer heat dissipation performance eats up most all of the boiling point delta since it will automatically cause the coolant temp to be higher just by using it.

I believe this is the reason that Rotax no longer recommends it.

Not surprising. I was the cooling engineer for an OEM engine manufacturer. IN the 80s there was lots of talk (propaganda) about going to propylene glycol. It was the same as 100% ethylene glycol. You are completely right, the higher Delta T across the engine, the lower specific heat, pushed the fluid up to the higher boiling point just to transfer the same heat from the engine as the original 50/50. The same actually goes for pure water too, lower temps until boiling, but no corrosion protection. Driving up temps sounds good until you think about bearing film thickness with elevated temps, oil degradation and hot spots in the heads due to incipient boiling and lower latent heat. A marketing novelty for any application that is high performance. Funny, my boss said I was a technological laggard for not adopting until I showed him the data. My 2 cents.