Air Plains, Inc. 300 Horse Engine Upgrade

I recently upgraded my 1976 Cessna 182P with the Continental IO-550 300 horse engine upgrade. I am experiencing heat through the plenum that the Installer cannot figure out. We have made sure that the valves are completely closed but are not certain whether the flap in the heat box is somehow being opened, or if there is another source or issue.

I am curious if anyone else has had the issue or heard of someone else having the issue.


  • Scott ShererScott Sherer COO Forum Moderator

    One of our authors, Scott Sellers, has the 300hp upgrade on his 182RG. He's on this forum weekly, standby!

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Hello lonelyr,

    The AirPlains 300XP conversion on our R182 uses the Lycoming IO-540-K1G5 but regardless of engine type the heat is drawn off the right side exhaust system through the warm air valve you mention. The body of that assembly is fiberglass and age can cause them to deform, making it more difficult for the valve to seal. On our 182P we reinforced the fiberglass body with aluminum so it could be firmly mounted at the firewall connection. I have seen residual heat at the duct vent in the cabin where it remains warm to the touch due to incomplete sealing of the valve. It is possible that in-flight vibration could contribute to poor sealing of the valve that appears to be sealed well on the ground. However if you are sure this valve is sealing well, then I am not aware of another source for causing heat to enter the cabin. Be sure to keep an eye on your digital CO monitor as well to make sure all is well.

    Scott Sellers

  • One other comment on this item. I recently saw a machined aluminum replacement for the orginal fiberglass part. The parts manual lists it as 1253032-1 heater body - valve assembly. Googling the part number finds no mention of an aluminum option. Maybe someone else is familar with this or other alternatives. FYI

    Scott Sellers

  • i had the same problem on my 182p. The flapper was not mounted flush with the metal flange and allowed hot air to continuously go into the cabin. I ended up using high temp RTV to create a gasket on the flange and no longer have problems. There was a discussion thread on my problem back in 2020.

  • The discussion in March of 2020 entitled “Cabin heat will not shut off completely, 182P”

    has all of the info

  • My 182P is a 1976 as well. Probably had the same problem. After extensive investigation, putting a light into the plenum and looking into the front of the hole where the hose attaches, I found light coming through the inboard side of the closed flapper valve. I would be happy to talk with you off-line for more details.

Sign In or Register to comment.