Need Advice Fixing '79 M20J Overhead Vent Leaks

[pwhicks]

We just did a major Avionics update to our '79 M20J.  Several of the overhead plastics cracked and needed replacement and repair when the overhead was taken down for the Aspen and Garmin's Antenna installations.

 

This is a Dorsal Vent model year...probably one of the first from the factory as it is SN 767.

 

We now have pretty significant leaks in the rear and barely any air volume at the pilot / F.O. seats.  I think the major leak is right behind the front seats at that overhead joint.

 

Does anyone have any advice on a way for me to seal that back up? 

 

I read in another thread someone mentioning that each eyeball vent was connected a hose and it had hurricane volume.  I can conceive building a dam towards the rear with hose inputs and using hoses, but don't know if that is the right way to go and where to start...

 

We did the Spatial Interior upgrade and new carpet as well during the Avionics upgrade.  I'll post some pics after she is back together after our annual finishes soon.

 

Thank you!

 

Paul

N201A

 

[M20F-1968]

There is one aluminum duct (about 3") that comes from the NACA duct on the dorsal fin.  There is a flapper valve which is cable operated in that duct.  This connects to a manifold with 4 flexible hoses, each of which connect to the wemac (eyeball) vents with a 90 degree adapter.  If you drop the ceiling it will be obvious and you can check all the connections.  The manifold is probably behind the hat rack rear partition.

 

John Breda

[pwhicks]

I was present when the ceiling was down.  It was sealed like a Plenum and has no hoses.  It had black goop stuff in between the panels.  I like what you described better.  I wonder if mine was prior to that design or if it was a "bad mod" later in the plane's life.

 

Where is the "flapper valve" connected to for the valve operation?  On my console I have a Vent, Heat, and Defrost.

 

The Vent and Heat basically both control the air coming out of the bottom of the center console.

[carusoam]

PW,

You may want to include the year of your J with your avatar data too.

People will be able to help you better.

By the time some people realize they can help, the data in title of thread gets washed out of memory...

Best regards,

-a-

[pwhicks]

It is a '79 J Manufactured in 12/1978 24-767 SN.

[pwhicks]

Here are some pictures I took today as seen from the Battery Access Panel.

 

http://mooneyspace.com/gallery/image/36844-/

http://mooneyspace.com/gallery/image/36843-2015-07-15-114327/

http://mooneyspace.com/gallery/image/36842-2015-07-15-114254/

[KSMooniac]

In front of that plenum you should find the 4 individual hoses that go to each vent.  You'll need to pull the headliner down to gain access, unfortunately.

 

Also, you could use some Corrosion X or similar.

[82Mike]

This is soooo funny just today we replaced all 4 of our vent hoses. The original hose material was "Lara aero duct". That is no longer made in the 1 1/2 inch and 1 1/4 inch sizes you need. So I contacted Steve at Mooney, you can use CEET or SCAT hoses. You will need 2 5 foot sections of CEET 4 (this is 1 1/4 inch, but it is on back order at spruce so you can use SCET it is about 2 per foot more. You will also need 2 9 foot pieces of CEET 5 (this is the 1 1/2 size and Spruce has it). We choose to silicone, hose clamp and but a small screw into the nipple where the hoses go. Your set up is exactly what I have in my 82. It is a pain to take the headliner down but it works great!

[Bjhdmdpa]

This is a funny thread. I have almost zero air flow on my m20c and spent close to 500 in mechanic time to quote fix the problem and it had no effect on improving flow through the overhead vent system. I'm back to the drawing board as these FL summers are cooking me like a rotisserie chicken.

[Andy95W]

This is a funny thread. I have almost zero air flow on my m20c and spent close to 500 in mechanic time to quote fix the problem and it had no effect on improving flow through the overhead vent system. I'm back to the drawing board as these FL summers are cooking me like a rotisserie chicken.

Welcome to MooneySpace!

The overhead vent system on our vintage M20C's is very different from the M20J that the folks above are talking about. Ours used the overhead scoop, theirs was part of the dorsal fin. Even the overhead system for the M20C/D/E/F/G was redesigned sometime between 1964 and 1967. This was all an attempt to make an inadequate system better.

If you are at all handy with tools, you are probably best off removing your headliner and doing the work yourself. You will end up learning how the thing is put together and how it works, rather than paying a mechanic to learn your airplane before he tries to fix it. Not many airplane mechanics are left around that have experience with our overhead vent systems unless you take it to a Mooney Service Center that has been around a long time (like Don Maxwell, Dugosh, LASAR, etc.)

You are permitted to remove and install your interior pieces as part of Preventative Maintenance per the FAR's. Reconnecting a hose or cleaning out a mouse's nest while you are there would be kosher too. If nothing else, you can save money by removing and installing your interior before handing off your plane to your mechanic. Speaking from experience: mechanics hate doing that, but we like actually fixing stuff once the interior is out.

[ArtVandelay]

Is there a "how to" on removing interior. Some stuff looks obvious (just remove screws), others like kick panel on the rear bench is not.

[Dale Logsdon]

You might want to check where the air is flowing out of your cabin. 

 

Airflow in won't be good if there is no place for it to exit.

[Andy95W]

Is there a "how to" on removing interior. Some stuff looks obvious (just remove screws), others like kick panel on the rear bench is not.

I've never found a how-to because every airplane is different. Not just by manufacturer, but if the airplane is more than 20 years old, it'll be different than even its own make and model. That's one of the reasons that mechanics hate interior removal and installation.

Your best bet is to just learn your interior yourself, with all of its own quirks and nuances. Ask advice from other owners and mechanics, a lot of the knowledge is transferable but still not the same.

And after you do it one time you'll never again question why you got charged so many hours for what seems like it should be a pretty easy job.

[RLCarter]

This is a funny thread. I have almost zero air flow on my m20c and spent close to 500 in mechanic time to quote fix the problem and it had no effect on improving flow through the overhead vent system. I'm back to the drawing board as these FL summers are cooking me like a rotisserie chicken.

Not to hijack the tread but when I had the headliner out I re-sealed (aluminum tape) the plenum because the factory tape wasn't sealing allowing air out between the headliner and the roof skins, also check the vent just inside the hat rack. The vent is the exit and has a screen in it, a buddies plane had the screen plugged with overspray from being painted twice.

[Guest]

This is soooo funny just today we replaced all 4 of our vent hoses. The original hose material was "Lara aero duct". That is no longer made in the 1 1/2 inch and 1 1/4 inch sizes you need. So I contacted Steve at Mooney, you can use CEET or SCAT hoses. You will need 2 5 foot sections of CEET 4 (this is 1 1/4 inch, but it is on back order at spruce so you can use SCET it is about 2 per foot more. You will also need 2 9 foot pieces of CEET 5 (this is the 1 1/2 size and Spruce has it). We choose to silicone, hose clamp and but a small screw into the nipple where the hoses go. Your set up is exactly what I have in my 82. It is a pain to take the headliner down but it works great!

To clarify CAT, CEET, SCAT, SCEET hoses and sizing, all are based on ID of the hose or the OD of the fitting. Two vowels denotes two ply construction. All are measured in 1/4" increments, ie -4 is 1" diameter, -5 is 1 1/4" diameter.

Clarence