Hot Air... Fixable or Expected?

[ArtVandelay]

Flew my new to me ‘65 E home from ND last week. Definitely got a hot air all the time situation that will need resolved. Serious heat from the under panel vents. Not serious cool. All heat all the time. Felt ok at 9500. Not so much at 3500. 

The other thing to check is the carbon monoxide level when heat is on. A hole in the muffler can end up forcing exhaust gases directly into the cabin.

[Shadrach]

26 minutes ago, Echo said:

Flew my new to me ‘65 E home from ND last week. Definitely got a hot air all the time situation that will need resolved. Serious heat from the under panel vents. Not serious cool. All heat all the time. Felt ok at 9500. Not so much at 3500. 

Reads like your heater box needs some attention as well as everything downstream.  The hoses are kind of PITA to change on the vintage birds.  They are frequently neglected.  As a result, they leak air where you don't want it and have low flow where you do want it (I'm looking at you defrost plenum).  Mine has two scat tubes that are grafted together to form a Y. Fabricating the replacement was ridiculously time consuming. I am 99% sure that it came from the factory that way but it is not shown in the IPC. 

While you're in there, if yours still has a Brittain PC or AP, it would be a good time to inspect/replace all of the vac hoses (useful life of~7years).  They can look OK at first glance but when stretched even a little open up like swiss cheese.  They fail from the outside in so even when in horrible shape, continue to hold vacuum.

The good news is that none of the materials required are expensive.  Just takes time...more than you might think.

[Echo]

5 hours ago, Shadrach said:

Reads like your heater box needs some attention as well as everything downstream.  The hoses are kind of PITA to change on the vintage birds.  They are frequently neglected.  As a result, they leak air where you don't want it and have low flow where you do want it (I'm looking at you defrost plenum).  Mine has two scat tubes that are grafted together to form a Y. Fabricating the replacement was ridiculously time consuming. I am 99% sure that it came from the factory that way but it is not shown in the IPC. 

While you're in there, if yours still has a Brittain PC or AP, it would be a good time to inspect/replace all of the vac hoses (useful life of~7years).  They can look OK at first glance but when stretched even a little open up like swiss cheese.  They fail from the outside in so even when in horrible shape, continue to hold vacuum.

The good news is that none of the materials required are expensive.  Just takes time...more than you might think.

Thanks Ross. Scat looks good and P.C. IS operational as is step. Likely that “mixer”. Scott 

[Shadrach]

6 minutes ago, Echo said:

Thanks Ross. Scat looks good and P.C. IS operational as is step. Likely that “mixer”. Scott 

I’m sure it’s the mixer.

PC will operate even with deteriorated tubing. When I did my first owner assist annual, I could not believe the tubing was signed off during previous annual. It was the texture of a dry rotted rubber band. It still functioned but it had every right to fail.

[Echo]

3 hours ago, Shadrach said:

I’m sure it’s the mixer.

PC will operate even with deteriorated tubing. When I did my first owner assist annual, I could not believe the tubing was signed off during previous annual. It was the texture of a dry rotted rubber band. It still functioned but it had every right to fail.

Down my list as PC is functioning well, but eventually will likely need addressed  

[gmonnig]

I did a lot of flying this last week and figured out a few things. The heater does blast hot air with very little vent air mixing, like barely cracked open. I think pulling too much vent air will obviously dilute the air too much. Some of the problems I had last winter were from overhead vents leaking (which were fixed) and also realizing that the avionics cooling air duct was on all winter long. So straight cold air on your legs. I never even noticed the avionics air lever until I replaced the nasty old tubing. Closing that would've made a substantial difference in feet comfort. 

[Keith20EH]

On my E, same problem as others, too much hot air.  I checked the mixing valve rigging, new scat etc.  I fixed it this summer by closing off part of the opening that allows air through the muffler shroud for the heater.  It seemed I just had way too much volume of air.  I made a cover plate of light aluminum, used an existing fastener on the cooling baffles, and closed off less than 1/2 of the opening.  No more hot feet in the summer. Easily removed at the first frost.  See highlighted area on attached screenshot.  

Edited September 9, 2023 by Keith20EH