Rotax 912UL coolant liquid

by Przemysław Wiśniewski in 912 / 914 Technical Questions 7 years ago

Hi.
If changing conventional liquid to EVANS npg+ is mandatory on 912UL? I found some documents about certified engines but this is not certified.
Engine is new on guaranty.

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Re: Rotax 912UL coolant liquid

by Roger Lee » 7 years ago

Roger Lee

127 5.21k 4.79k

Rotax at one short interval was okay with Evans. Not any more. That's an old document and has been superseded. Don't use it. It also carries with it a 20F-30F heat penalty. Water based coolant does a much better job of heat transfer. Evans was only good at helping a boil over and if your plane does that then it may be time to either change the expansion cap or find out why it boils over and correct that problem.

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

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Re: Rotax 912UL coolant liquid

by Ian Rees » 7 years ago

Ian Rees

6 42 0

According to the latest edition of the Rotax 912 Installation Manual, Ed 2/Rev.1, Feb, 01/2015 makes this statement.

Chapter 75-00-00 - Cooling System,
Page 7
Engine types, Without suffix 01
1.3) Coolant Types
Two types of coolant are permitted.
1. Conventional coolant
2. Waterless Coolant

So to clarify the earlier statement, waterless coolants are permitted which is not the same as saying "was okay, but not anymore".
However, as Roger makes note, waterless coolant will be slightly hotter.
The above reference from Rotax mentions 41-50F hotter which is 5-10 DegC.

Also, Suffix 01 engines are only permitted glycol coolants. (Page 9).
This is important.
Prior to Suffix 01, both Waterless coolant and 50/50% Water/Glycol are permitted.
Suffix 01 changes to only conventional coolants permitted.

See above reference for full details.

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Re: Rotax 912UL coolant liquid

by Roger Lee » 7 years ago

Roger Lee

127 5.21k 4.79k

This is right off the SI. Maybe this will help.

Waterless coolant for engine types 912/914 Series
■ CAUTION: Not released for engine types 912 i Series and 912/914 Series with cylinder head version
Suffix - 01.
An advantage of waterless coolants is their high boiling point which prevents “boiling“ of the cooling system.
However, its specific thermal capacity is lower than of conventional coolant which resulting in slightly higher
running temperatures.
The cooling system of ROTAX® engine types 912/914 Series (without Suffix - 01) is designed for operation with
waterless coolant and thus must not be modified, i.e. drainage or ventilation holes must not be closed.
■ CAUTION: The certification and determination of the correct coolant type must be conducted by the aircraft
manufacturer. As each aircraft type has different characteristics, testing must be done to
determine the most suitable coolant and instrumentation for each aircraft type.
Recommended coolant (100% concentrate)
◆ NOTE: NPG+/NGPR/NPG+C are not available anymore and are replaced by the successor product
Aero Cool 180°.
■ CAUTION: Aero Cool 180° contraction point is approx. -23 °C (-10 °F) . It will not freeze and expand like
conventional coolant. Do not use if conditions expose the engine to non-operational temperatures
below -23 °C (-10 °F).
M n arke/brand Bezeichnung/descriptio
E 0 VANS® Aero Cool 18
4.3.1) Warnings for operating with waterless coolant
- Water or coolant containing water must never be added to the cooling system!
- The max. water content must not exceed 3.6 %; it can be tested using a Brix refractometer.
- Any water present in the cooling system is separated out as vapor. This can cause the cooling system
to fail due to insufficient coolant quantity.
- If Aero Cool 180° is not available locally for servicing the cooling system, a conventional coolant based
on pure 100% ethylene glycol can be used temporarily. However, the coolant must be replaced again
with Aero Cool 180° within the next 15 days.
■ CAUTION: As some conventional coolants are available in a pre-mixed formula (water added) be sure
to add only 100% pure ethylene glycol if Aero Cool 180° is not available.
■ CAUTION: The above warnings are taken from the manufacturer’s users manual, however the
original text and description in the users manual is binding.

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

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Re: Rotax 912UL coolant liquid

by William Campbell » 6 years ago

William Campbell

15 25 43

Hi Roger. My question is about the 912UL radiator and over flow tank. On my engine I have a clear hose from the radiator down to the overflow tank. On the initial fill I purposely raise the overflow tank with coolant in it to fill up the clear overflow line and fill the radiator cap opening to the top and then I quickly put the radiator cap on and lower the overflow down to its original position. At that point I know the system is pretty much free of air and it any remains it will clear itself on a few engine cycles. Everything works fine. I have a low and high mark on my overflow tank that I monitor at least before each flight to see if the coolant level remains relatively consistent.

Today I had a Rotax approved mechanic doing my annual compliance inspection. He reached over and was going to remove my radiator cap and I immediately stopped him. He could not understand why I was so excited. I told him I would lose the fluid in the hose to the over flow tank and he said that is no problem. He actually said as long as he looks under the cap and there is fluid there that everything is ok. He said that the overflow hose does not have to be full of fluid. Well I strongly disagreed telling him that it is a closed system and that the overflow hose must be full at the top for the radiator cap opening to the overflow tank for the system to cycle correctly between hot and cold cycles. Am I missing something here?

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Re: Rotax 912UL coolant liquid

by Roger Lee » 6 years ago

Roger Lee

127 5.21k 4.79k

I just fill the expansion tank on top and fill the reservoir tank to the level I want and don’t worry about the hose. I don’t know anyone that worriers about the hose. The closed system is up the to radiator cap. The reservoir is open to atmospheric pressure. When the expansion tank cap opens to draw coolant up from the reservoir it should not have any issues. If the cap opens to vent hot coolant to the reservoir then it will vent out the air.

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

Thank you said by: William Campbell

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Rotax 912UL coolant liquid

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