I'm a new plane owner (912is) with a new plane (70hrs).  So far it has been performing exceptionally well.  My home airport has a rather long taxi to the runup area and I noticed yesterday that the coolant temps were running into the red after run-up and waiting to take off.  After taking off, the coolant came back to normal and everything was fine.  Ambient temps are around 65F.

Flew to an airport an hour away overnight and has a very short taxi area and I was overheating very quickly, in fact Lane A was flashing; maybe 68F ambient.   Saw the coolant issue, reduced throttle.  Lane A reset did nothing and eventually went solid red.   Taxi'd back to parking to let it cool for about 20 mins.  Startup was fine, temps were climbing again, but got an immediate release and took-off.   Temps were fine the whole way home.  There was a stiff 15kt crosswind in the run-up area that may have disrupted airflow across the radiator.

As we start getting into the summer, temps will get over 90F regularly and if I'm having issues now...I can't see summer flying even being an option.

Details / questions:

1. I was using 91Mogas exclusively until I went to the new airport.   They topped off with 100LL the night before (at startup 1/2 was 91 and 1/2 was 100LL)

2. It's using Dexcool Longlife GM 93170402.  Overflow tank is about 1" above the min line and hasn't moved as far as I can tell.  Should I top it off?  Should I use something else?  I don't think it's 50/50...but I don't really know to be honest.

3. I recently upgraded the prop from a basic manufacturer provided prop to a better aftermarket carbon fiber prop.  The old prop was wider (very scientific), so wondering if that was giving better airflow over the radiator. Ground taxi at the same RPM (1700) feels higher with the new prop.

4. When I got home and let the engine cool, I opened the coolant cap and it was full to the top.

5. In flight temps are perfectly fine; about 100-110F over ambient at high cruise.   50F air temp, 160F coolant temp.

6. Instead of the run-up area full stop, 4,000RPM lane check procedure...can I instead do it during taxi at lower RPM (since we are just checking the lights are working)?   As far as full-power, I'm checking that at the end of the runway anyways before I release the brake.

7. Could I install a 12v fan on the backside of the radiator; perhaps with a cockpit switch to make it simple?  If so...where could I find one?

Thanks for the ideas....


  • Re: 912is High Coolant Temp - Fan?

    by » 6 months ago

    I know that others have installed a 12v fan which worked in a similar situation. there are aftermarket cooling fans from automotive that work and some have temp controlled switches but that depends on your setup as you say a simple switch would work fine

    However cooling and airflow is very dependent on design of aircraft and cowlings. Therefore I would ask people with the same aircraft this question.In other words I think this is more of an air-frame question.



  • Re: 912is High Coolant Temp - Fan?

    by » 6 months ago

    What model of plane is it?

    If you're having a problem, someone else with the same model has probably already solved it.


    "There was a stiff 15kt crosswind in the run-up area that may have disrupted airflow across the radiator."

    Is there a reason that you did not point the nose into the wind during runup?

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated.

  • Re: 912is High Coolant Temp - Fan?

    by » 6 months ago

    First thing I would do is drain the existing coolant and replace with either Prestone or Shellzone Dexcool premixed so you know you have a 50/50 mix.




  • Re: 912is High Coolant Temp - Fan?

    by » 6 months ago

    I wasn’t pointed directly into the wind because the airport layout doesn’t allow it.  They have defined lineup positions for the run up that are offset from the runway and the wind at the time.  And yes, there were other planes filling every spot and I wasn’t not about to be the person not following the rules.  

    25147_2_3C0F6DC2-75EC-471B-B094-FBFA2DB539F4.png (You do not have access to download this file.)

  • Re: 912is High Coolant Temp - Fan?

    by » 6 months ago

    Am I better have a 50/50 mix with water or not?

    if there is a mix and it still overheats / boils that’s a big problem.

    if it’s concentrate then I have a higher boil point.


You do not have permissions to reply to this topic.