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Last weekend on my climb out I ended up exceeding the max coolant temp. I immediately pulled back throttle and landed. Logs showed 20s at 252F (4F over max). I fixed the issue (which was winter airflow restriction). After this I flew again and temps didn't exceed 210F. 

Reviewing the manuals I am required to do a coolant system test. I attempted to do this today. Following the line maintenance manual I pressurized the system to check for pressure of the rad cap overflow. Turns out I am seeing and hearing air at the overflow tank at only 10psi. Minimum is 17.6 psi. I'll have to order a new cap and re-test as that's the requirement. 

Now, my question here - is there a way I could have messed up to cause a lower pressure release? It was air and minimal fluid coming out through the hose to the overflow. I kept the pressure for several minutes and inspected all connections of the system and found no signs of leaking. 

I put everything back together and did a full run-up getting the coolant temp up to about 176F. Afterwards I was not able to detect any leakage in the system and it did not appear as if there was anything going to the overflow. 

 

  • Re: Coolant overheat system testing

    by » one month ago


    Hi Keith

    Caps fail, they are mechanical in how the pressure works against the release spring.  Rotax used to use a .9bar cap and years ago upped it to 1.2bar.  if it was operating at 10 psi (about .7 bar) it should definitely be replaced.  

    The question is for how long did the overheat take place?  if it was only 20 seconds no damage would occur to the head material so dont worry too much. I would recommend a check of the cap on the annual. The information is in the maintenance manual line, MML. 

    Cheers


  • Re: Coolant overheat system testing

    by » one month ago


    I appreciate the response. I may actually have the old one. Engine is new from 2014 and didn't go into service until 2021. I'll order up a replacement. I also just read here somewhere that taking it on and off all the time (pre-flight checks) isn't the best idea either? (which I've always done). 


    Thank you said by: Karl Kistler

  • Re: Coolant overheat system testing

    by » one month ago


    Hi again Keith

    Yes they gave you good advice.  The only time you need to really remove it is at the annual.  On and off too many times can damage the rubber gaskets sometimes.  You need to just check your overflow bottle on pre-flight.  As long as it is fine and the level is fine best to leave it alone. Just look at the top of the cap for the pressure.  You will see clearly if it is the old .9 bar or the newer 1.2 bar.  Certinally put on the newer one with the higher pressure.  (I think 2014 will be a 1.2)

    Cheers

     

     


  • Re: Coolant overheat system testing

    by » 6 weeks ago


    Got a new cap. Old one was the newer 1.2 bar. It took two attempts to re-test the pressure, but it did hold to 18 psi and so everything looks good. Thanks.


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