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Carbon Monoxide Leak

P

psalys

Member
Patron
I have a carbon monoxide leak in my RV-12iS that I can't track down. The engine is a Rotax 912iS. It only happens on climb out with full power. When I pull the power back to ECO mode it goes away. I'm getting numbers on my Aeromedics CO detector of 15 to 30ppm.

I have checked the firewall, the cabin heat vents, the fresh air vents with no success. Also, I have not found cracks in the engine exhaust tubes per the service bulletin.

My current thought is that the CO is not coming through the firewall, but it's coming from the exhaust pipe and then leaking in through the wing seals and then through the wing spar holes. I think it only happens at full power because the engine isn't making significant CO when the throttle is pulled back into ECO mode.

Has anyone had this problem and been able to solve it?

Thanks,
Patrick
 
Hey try looking at the sleeve connection on the #1 cylinder exhaust tube.

The recent SB installs a Flat Spring that prevents that connection from separating.

I didn't receive any CO warnings, but i noticed my muffler was moving around inside the Lower cowling exit. When i traced up to the #1 exhaust tubes, I found the sleeve had lengthened out by almost an inch!

SB-00064 called on resetting that tube and installing the springs to keep that from happening.

My only other theory is if the wind is just right, the exhaust fumes that flow down the belly may get "drawn" into the cabin via the wing root openings, or the landing gear insertion points to the fuselage.

All theories of course!
 
Check your canopy seals

I’d recommend taking a close look at your canopy seals. If you see daylight between the seal and the frame, it can create outflow. The inflow has to come from somewhere. It can often be from below the airplane.
 
I had something similar happen, so I stuffed some cushion foam in the openings around the gear legs to seal them and it seemed to help a lot.

John Salak
RV-12 N896HS
 
There is a good chance that the exhaust gases coming in from the rear through the tail cone. Check this out and seal gaps if necessary.
I had the exact same happen on my RV-7 - little carbon monoxide during climb with rich power setting going away in cruise mode.
 
I recently had an experience similar to WJaviation described above. My RV12iS is equipped with an Aithre SHIELD EX 3.0 CO detector. Over the first 200+ hours of flight, CO readings were always 0. I then began to see readings up to 15PPM, first on climb out, and then during taxi.

This was a clear change from previous CO readings.

Investigation revealed the upper slip joint on cylinder 1 had slipped out ~1 inch and jammed. Once fixed (SB-00064) and lubricated, the problem resolved. Additional details and pictures are on my builder's blog. https://eaabuilderslog.org/?blproject&proj=7cA2iACEi
 
bernsbm said:
I recently had an experience similar to WJaviation described above. My RV12iS is equipped with an Aithre SHIELD EX 3.0 CO detector. Over the first 200+ hours of flight, CO readings were always 0. I then began to see readings up to 15PPM, first on climb out, and then during taxi.

This was a clear change from previous CO readings.

Investigation revealed the upper slip joint on cylinder 1 had slipped out ~1 inch and jammed. Once fixed (SB-00064) and lubricated, the problem resolved. Additional details and pictures are on my builder's blog. https://eaabuilderslog.org/?blproject&proj=7cA2iACEi
Click to expand...

Are you supposed to use two springs on the one joint? or one spring on each joint?

In your blog picture, it looks like you applied both flat springs to the upper sleeve rather than one on each. Upper and Lower.
 
Thanks for all the replys

I still have my original non-slip joint exhaust tubes (haven't found any cracks yet), so I can't blame it on that. I will check the other things you all suggested.

Thanks,

Patrick
 
For reference, I usually see 0 ppm.. But occasionally see 2-3 ppm, typically during a climb. I do NOT have wing root seals installed yet.. so I imagine exhaust is in the windstream.. high pressure under the wing.. air is forced into the cabin at the wing root spar.. or, less likely, the landing gear mount area.

Also, I occasionally see areas around the muffler ball joints where the anti-seize compound looks like it got blown out of the joint.. and onto the exhaust tubes. I'm sure during engine startup, some exhaust escapes from those joints. its not an air-tight seal.. but the firewall is pretty close to being 100% sealed.. thats important too.
 
WJaviation said:
Are you supposed to use two springs on the one joint? or one spring on each joint?

In your blog picture, it looks like you applied both flat springs to the upper sleeve rather than one on each. Upper and Lower.
Click to expand...

Good pickup. My "repair" was done prior to release of the SB, and has been working well. However, you are correct, the SB shows one spring on each slip joint.
 
CO fumes

Hello there;

Look at your fuel line connections at the engine side first. any discolors?

Then look at fuel lines from inside the firewall to check for leaks... Very hard to get to; you have to remove the petals! Grin....

Place paper under console where all four lines connects up to see
it that area is leaking.

Then proceed to the back fuel lines.

Good luck....

Charles
 
Problem solved

I just finished the condition inspection and found a few holes in the SCAT tubing for the cabin heat. I didn't think this would be the problem because opening or closing the cabin heat doors down by the pedals made no difference in my CO readings.

Now my CO read 0 like it used to and I am happy. I'm a little embarrassed that I didn't look closer at the likely culprit to begin with.

Thank you all for you suggestions.

Patrick
 
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