fbpx

 

Just got the plane back from annual and it’s having temp issues.

912 with aprox 450 hrs since new.

oil temp past 250 at 75% power 

cht approaching 280 after running for 30 min.

carb needle clips in factory positions.

Compression on cylinder 3 was low 60/87. This is new, it was checked 5 hrs ago and read 70/80.

rotech asked the mechanic to tap on the valve but he was sure this wouldn’t fix the issue.


The mechanic got the #3 head off. 

The exhaust valve is moving but apparently it’s leaking because that cylinder is 60/87.

could this really have been the cause of the overheating?

I checked the new muffler with an inspection camera and it looks the same as the old one inside. It appears all the baffling and pipes are correct from what I can tell but obviously you can’t check the entire assembly without cutting into the muffler.

This is very strange coincidence that as soon as we get the plane back it’s overheating and we have a leaking exhaust valve. Ofcourse they might not be related but it would be one heck of a coincidence.

Are we chasing two different problems or is this all part of the same cause?

 

  • Re: 912 overheating after maintenance part 2

    by » 4 months ago


    The sudden (5 hr) change in leak down test seems a bit strange, unless you have overheated the engine.

    I would check all the basics before imagining/exploring more serious problems.

    Basics;

    Make sure there are no air pockets in coolant/oil circuits.

    No kinked pipes in oil/coolant circuit -  can occurred (unlikely) only when engine hot (in flight) if routing (tight bends) and or quality of hoses not the best.

    No change to cowling  inlet/outlet air (including forgotten tape/paper/etc that may be covering oil/coolant radiators).

    Prop pitch has not been altered - are you getting 5200RPM on a WOT static/ground run?

    Oil coolant change from previous?

     

    "oil temp 250 at 75% power"  - (121C) is this in level flight ? some many (?) minutes after climb ?

    "cht approaching 280 after running for 30 min."(138C) is this stationary running on the ground? taxying? or  in flight?

     


  • Re: 912 overheating after maintenance part 2

    by » 4 months ago


    Nick,

    In the last entry of your first thread (part 1) you mention that after the maintenance your fuel burn was also 30% lower.  That’s the first time I saw that mentioned, and it’s not mentioned again in this new thread.  Is this actually the case? 


  • Re: 912 overheating after maintenance part 2

    by » 4 months ago


    You think the #3 low compression is related to the work somehow? Carbon build up? Or perhaps something that fell into the valve seat?

     

    "Make sure there are no air pockets in coolant/oil circuits."

    No kinked pipes in oil/coolant circuit -  can occurred (unlikely) only when engine hot (in flight) if routing (tight bends) and or quality of hoses not the best.

    No change to cowling  inlet/outlet air (including forgotten tape/paper/etc that may be covering oil/coolant radiators).

    "Prop pitch has not been altered - are you getting 5200RPM on a WOT static/ground run?"

    -Constant speed prop with a reduction gear ratio of 2.2727:1. RPM is prop rpm. 

    "Oil coolant change from previous?"

    -Oil and coolant are the same as was always used. Aeroshell sport plus 4 and Dex cool. 

    "oil temp 250 at 75% power"  - (121C) is this in level flight ? some many (?) minutes after climb ?"

    - Oil 250 F, 75% power in level flight. CHT (which I've been told is water temp) was approaching 280 deg after 45 min to 1 hr level flight. It was getting hotter at full power in the climb. 

    "cht approaching 280 after running for 30 min."(138C) is this stationary running on the ground? taxying? or  in flight?

    -This was 2 laps around the pattern and hard running on the ground at 75% power. 


  • Re: 912 overheating after maintenance part 2

    by » 4 months ago


    Jeff Blakeslee wrote:

    Nick,

    In the last entry of your first thread (part 1) you mention that after the maintenance your fuel burn was also 30% lower.  That’s the first time I saw that mentioned, and it’s not mentioned again in this new thread.  Is this actually the case? 

    Hi Jeff, 

    Yeah, I used to burn 6 gph average over the last 5 years. I always thought it ran a little rich. 

    Post maintenance its burning 4-4.5 gph. 

    I Spoke to Ken at Rotech today (awesome mechanic), he looked at photos of the head with the suspected leaky exhaust valve. He believes the carbs or muffler are most likely the problem at this point. 

    I hope the current mechanic can fix it but he likes to work alone and I really don't want to be on the hook for corrective maintenance after the annual. I can TRY getting reimbursed but this is getting expensive. 

    Ken from Rotech recommended having the guys from Canada drive down to fix it. 


  • Re: 912 overheating after maintenance part 2

    by » 4 months ago


    What airplane is this in?

    What is the OAT when it is running hot?


    Walt

    my blog; waltsrv12.com


You do not have permissions to reply to this topic.