Help! I am getting carbon monoxide in my PA 22/20. I can't find the source. I have tried to seal up around the bungees and the muffler is ok with no leaks. I have a dot indicator and a more sensitive electronic sensor. I open the vents and the level will decrease. That won't work so well this winter and it is not a great solution now. It has a O360 and a leading edge exhaust system. The engine is high time. Any ideas would be great. Thanks.

I almost bought the farm in an old Taylorcraft F-19 due to carbon monoxide.
It occurred on a flight where I had been wallowing along a bit below maneuvering speed due to heavy turbulance.

It was an old, red, fully depreciated, rental at a Palo Alto club.
Turns out when you fly an old rag and tube plane a bit on the slow side, the exhaust, instead of going UNDER the plane ends up WRAPPING around the fuselage, and coming in through the door gaps where the seals had been gone for some time, and there exists a bit of low pressure area right about there also, which helps to suck that stuff in.

I had flown the same plane on long cross country flights with no problem.
BUT, sixty minutes of wallowing slow flight almost did me in.

Hope that helps

Chris C

I have tried new door seals. It did seem to show up during some turbulance the other day. It had been better the previous 8 hours. I get low levels (<20 ppm) all the time. The higher levels come after about an hour of flight, usually at 10-12,000 ft. The vents are usually open when low & slow. It's hot out there!

I've read about openings in the fuselage near the tail being the culprit for sucking CO into the cockpit.

Sounds like you need more fresh air leaks in the cabin!

How does the firewall look? Any holes that aren't sealed? If I remember correctly, there is an AD that requires the perimeter of the firewall and anything that goes through the firewall to be sealed with red silicone. You might want to check that little canoe-shaped fairing on the bottom of the fuselage that covers the hole for the bottom of the control column too. I seem to remember it had a gasket, but I could be wrong.

Good luck.

In the Cherokee world, gas fumes and C02 are sucked back into the cabin thru the tail opening slot for the stab. Low pressure pulls the exhaust into the rear of the fuselage and if the rear bulkhead or battery door isnt sealed well, you get fumes. Its difficult to seal at this area because the rear bulkhead only covers part of the fuselage. It is most pronounced in turbulence and when you chop the power and the mixture immediately goes full-rich. Hope this helps.

I will keep looking up front in the firewall area and recheck the muffler. The levels do not get higher with the use of cabin heat so I am thinking it may be coming from the tail area. Is there a way to seal that up? Does the co work its way through the upholstery? When I was orginally working on this problem, pluging the air leaks around the bungees helped a lot.

A muffler pin hole leak into the cabin heat jacket around it can cause the problem you have. You will have to tear it off to find it though. Good luck

Check to make sure your firewall seal mouldings are in place. I have seen these removed before on PA-22/20 and also installed incorectly. Since your aircraft was converted to a 20, they could have been left off acidentally. If you need the part #'s they are 14972-00, 14972-01 and 14973-00.

Brian.