Evans antifreeze

by Dennis Moore in 912 / 914 Technical Questions 10 years ago

I just watched "Care and Feeding of the 912 Rotax" by H. Paul Shuch and he states that when using Evans antifreeze you cannot put any water to bring up the level in averflow bottle. I put in approximately 4 ounces of 50/50 antifreeze in bottle before I saw the webinar and before I found out that Evans was in my machine. Does anyone think that this small amount of water could cause damage to engine or components?

Re: Evans antifreeze

by Roger Lee » 10 years ago

Roger Lee

126 5.13k 4.58k

Hi Dennis,

First having a little 50/50 mix with the Evans won't physically hurt anything. I say a little because I doubt your entire reservoir bottle has been induced into the main system. It will just put water into a waterless system and then loose the properties of the Evans.
If the coolant in your reservoir has not been swapping back and forth with the main cooling system you may not really have done anything. If it was a minute amount I doubt you have enough in the system to worry about. I would just drain the reservoir and fill with Evans. Many have moved away from Evans because it carries an additional heat penalty of 20F-30F over a 50/50 coolant. It tends to work well enough with open air engines, but in a tightly cowled engine may cause temps higher than what you want or need. Regular 50/50 coolant's boil temp is around 270F and Evans is 370F. It used to be recommended by Rotax for a short time, but they have moved away from that. Water absorbs and transfers heat better that Evans without any water. I tell people that if you have over heating problems then that needs to be addressed and don't put a band-aid on the problem with Evans. I live in the southwest desert (Tucson, AZ) and so do many other Rotax 912's and most of us do not have any overheat issues.

Food for thought:

If you don't have boil overs then it may be beneficial to move back to a 50/50 mix depending on what your temps are. With a 50/50 mix you could then just add distilled water or a little more 50/50 if you need a little top off in your reservoir tank.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Thank you said by: Dennis Moore

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Re: Evans antifreeze

by MARK JACKSON » 10 years ago

MARK JACKSON

12 332 11

Hi Dennis

where do you fly and what do you fly first of all.

If you wanted to stick with evans and you have not used the coolant in the overflow bottle, just syphon it out. As Roger says you probably haven't done anything.

I use Evans and swear by it. Its boiling point is +180c and freezes at -40c. You don't get any hotspots where you can get boiling of coolant that can cause detonation, and there are no corrosion problems. Its clean and non-toxic. It will last the life of the engine as it doesn't degrade with use. If i need to empty the coolant, I just run it through a filter and re-use it. It will make the engine run slightly hotter but as Roger says its not a problem in open air cooled engines like mine. If it is a cowled engine and you're flying in the desert, I would probably use 50/50 if there were cooling issues.

Mark

Thank you said by: Dennis Moore

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Re: Evans antifreeze

by Al C » 10 years ago

Al C

63 138 106

Hi Dennis,

I'll defer to Roger on the "having a little 50/50 mix with the Evans won't physically hurt anything." And agree it's possible that none of that water if added to the reservoir (surge/overflow cup) has even yet have entered the actual circulating cooling system.

Since you're heavily invested in the Evans coolant (it ain't cheap) and does have some advantages (supposedly never have to change it, no chance of electrolytic corrosion, and, yeah, higher boiling point) you might want to stay with it ... particularly if your engine oil and coolant aren't routinely running significantly over the optimal temps (optimal is about 215F).

That said, FWIW, I'd agree there are advantages to coolant/water mix..... one of which you already discovered, that you can top it up anywhere anytime with a bit of conventional coolant or distilled water without worrying that you've compromised your cooling system.
But, at the risk of getting off your topic, do want to point out that, although Rotax mentions 50/50 mix, and that's great for most uses, you can choose anywhere from 40% to 70% coolant and there are advantages to going lower or higher than 50% coolant.

Dex-Cool Boiling & Freezing Protection, °F (using a 15 lb pressure cap)

40% 260 -12F
50% boiling point 265 F Freezing point -34F
60% 270 -62F
70% 277 -90F

So one obvious reason for adjusting to other than 50/50 might be needing more freeze protection.
Less obvious is that although 40% boils a bit lower than 50% it transports heat better (the more water, the better the heat transfer ability) and might be suitable if you tend to run a bit hot.

Even less obvious is the reason we're trying running higher than 50% coolant ..... 60% or 65% coolant:
Like many Rotax ... ours tends to run a bit cool. Have to cover part of the radiators .... even in the summer ... to get it up to optimal temperature.
You could say our cooling system it TOO efficient.
With less water in the mix it is a tad less efficient at cooling and and comes up to optimal operating temps a bit faster sooner and stays there easier.

No advantage to ever using more than 70% conventional coolant as boiling point starts going down after that concentration. .... and heat transfer capacity starts going way down.

Al

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