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Hello Rotax forum members,

Since this is the first time I post something here (long time reader) I will introduce myself: I recently finished an Europa XS Monowheel and I have a 912ULS engine in it. The engine I have was purchased "rebuilt" from a Rotax authorized heavy maintenance facility. Not overhauled. The entire engine/gear box was disassembled, inspected, what needed to be new was replaced and in general looks like a good job. I did have a few issues with the accessories but all was easily fixed. The engine is SN 5,65X,XXX vintage (I think it was born around 2008). The engine now has 85 hours and has run well (we estimate 2000 hrs when it was pulled out of a CTLS and rebuilt)

I decided to change the oil today even if not at 100 hrs (oil was replaced also at 25 hrs). When I removed the oil tank plug I found that the first thing to come out briefly was an orange liquid. It wasn't much (tablespoon maybe, hard to tell) but it's clearly some sort of contamination. I can see a few droplets of the orange stuff in my funnel walls. Since my coolant is orange I assume it is coolant. It doesn't mix with the oil. The oil is quite dark but doesn't seem to have any water in suspension as it is pretty clear.

Since not much contamination was found I am going to replace the oil/filter and fly a few hours and inspect again. I did open the oil tank to clean and it was fairly quite clean once I wiped the oil off the wall. Couldn't see anything that looked like coolant inside despite some oil accumulated on the bottom screen tray. I'm also going to drain the fuel and replace with something else.

A few facts: My engine runs somewhat cool. Oil temp is around 180 when cruising (5000 RPM) in Florida summer and rarely goes up much more than that except during climb. I just came from a trip from SC to FL with the engine running good but oil temps were low (150 ish). During the trip I stopped for fuel at an airport with 93 Mogas. Not sure about the quality of that fuel and I have some doubts. The fuel was a bit yellowish but clear.

So my question is: Can coolant really get into the oil circuit? if so how? I was told this is very strange. Are there any seals in the head that will allow coolant to migrate to the oil?

The fuel pump does show a few drops on the drain hole but it nothing on the engine compartment looks dirty as if the pump leaked badly. I was told these drops are normal. I assume that since the water pump has an oil and water seal separated by a space with air it would be unlikely to see coolant get into the oil through here.

The coolant has gone down (expansion tank) since I first flew the airplane back in March but I just returned from a 7 hour trip and the level at the reservoir has not changed.

Is it possible for the coolant to make it to the oil?

Chris

 

 

 

 

 

 

  • Re: Coolant in the oil tank?

    by » 4 weeks ago


    It would be good to use the terms that Rotax uses.  When you say "expansion tank", are you talking about the tank with the pressure cap, or the overflow bottle?  I am not sure what you mean by "the reservoir".

    If you lose some coolant, you should notice it first in the overflow bottle, if things are generally working properly.  The amount in the expansion tank really should not go down until there is nothing left in the overflow bottle to draw from (the overflow bottle connection should be at the bottom of the bottle, connecting to the expansion tank just next to the pressure cap).

    Mogas generally is "yellowish", I would say.


  • Re: Coolant in the oil tank?

    by » 4 weeks ago


    I'm assuming you are seeing water in the oil tank.   I don't ever recall seeing water in the oil tank when I have changed the oil, but it seems like it could be very possible, depending on how you operate the engine.   Water is a byproduct of combustion and if the engine does not get up to a high enough temperature, it can accumulate.   I don't ever recall seeing this in my Rotax, but I have seen it in other aircraft engines. i.e. the owner starts the engine for 10 minutes every month.


  • Re: Coolant in the oil tank?

    by » 4 weeks ago


    I would suggest installing an oil thermostat to get those temperatures up high enough to vaporize the ambient moisture down there that is accumulating in your oil tank. I fly a Europa Trigear and had similar issues before installing a PermaCool thermostat.


  • Re: Coolant in the oil tank?

    by » 4 weeks ago


    I agree that you need to get oil temps up around 212F to boil off any condensation in the oil. For now you can use a strip of 2" aluminum tape across the radiator / cooler to get temps up. Then check the oil again after 25 hrs. You live in a humid wet climate so this is important. Try raising your cruising rpm too. Some of these things can be influanced by prop pitch.


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


  • Re: Coolant in the oil tank?

    by » 4 weeks ago


    I have the hotter version of the Thermostasis thermostat, and it is only 205 F. It does a good job of getting the oil temp to 205 quickly and keeping it there (within just a few degrees).

     


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