Need to repair air box

[TravelVeteran]

Need to repair my 1965 Mooney m20c air intake box. The carb heat flap hinges are worn. Would love any referrals or tips. Thank you!

[RLCarter]

Check with Spruce, pretty sure the sell the bushings (pivot point). 

[TravelVeteran]

Looks like it’s worn through the metal as well not just the bushing needs to be replaced

[47U]

LASAR has a kit.  It’s got everything you need.  New carb heat door shaft, bushings, and the flapper in the hot air dump valve, if you need that.  

My before and after... like yours, my bearings were so worn the shaft had eaten into the box.  I made a little patch to save it and sealed it up with some red high temp RTV.  Yours might be farther gone than mine.  If you need a new air box, check with Loewen Mooney Salvage.  

[TravelVeteran]

[TravelVeteran]

  On 11/25/2020 at 6:58 PM, 47U said:

LASAR has a kit.  It’s got everything you need.  New carb heat door shaft, bushings, and the flapper in the hot air dump valve, if you need that.  

My before and after... like yours, my bearings were so worn the shaft had eaten into the box.  I made a little patch to save it and sealed it up with some red high temp RTV.  Yours might be farther gone than mine.  If you need a new air box, check with Loewen Mooney Salvage.  

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How much was this repair kit? Thanks!

[mike20papa]

A few years back I rebuilt the airbox on my A model.  I used these PMA'd bearings from McFarland, fabricated my own shaft, door, etc.  Blessed by my A&P/IA I wrote it all up and sent in a 337.

https://www.mcfarlaneaviation.com/products/product/MC955/

Of course, the photos (always) load inverted .. sorry.

[TravelVeteran]

Anyone know what this tube is for? (Number 29 in the diagram). 
 

What attaches to it? What is the purpose of it? 
 

 

Edited November 26, 2020 by TravelVeteran

[47U]

  On 11/25/2020 at 8:43 PM, TravelVeteran said:

How much was this repair kit? Thanks!

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Better sit down... It was 10 years ago, but I think .7 or .8 amu at that time.  It comes with the blue-line drawing which contained all the applicable notes.  You get the flapper door, a new shaft, two new (plain) end bearings, the dump valve flapper and its bearing housing.  Even the wire controlling the dump valve position and those connecting terminals were included. 

[47U]

  On 11/26/2020 at 12:25 AM, TravelVeteran said:

Anyone know what this tube is for? (Number 29 in the diagram).

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That’s the carb heat dump tube.  When the carb heat flapper in the air intake is up (carb heat off) that dump valve is open to keep circulating cool air around the muffler.  When the flapper door is down (carb heat on) that valve is closed.  

There’s supposed to be a duct connected to that valve that dumps out the left cowl flap.  

[TravelVeteran]

  On 11/26/2020 at 12:30 AM, 47U said:

That’s the carb heat dump tube.  When the carb heat flapper in the air intake is up (carb heat off) that dump valve is open to keep circulating cool air around the muffler.  When the flapper door is down (carb heat on) that valve is closed.  

There’s supposed to be a duct connected to that valve that dumps out the left cowl flap.  

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Mine connects to the front of my cowl. Ram air?  Maybe it’s connected to the wrong thing? 

[47U]

  On 11/25/2020 at 11:59 PM, mike20papa said:

A few years back I rebuilt the airbox on my A model.  I used these PMA'd bearings from McFarland, fabricated my own shaft, door, etc.  Blessed by my A&P/IA I wrote it all up and sent in a 337.

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Someone I know had a ‘62 C and had those needle bearings on the carb door flapper.  He was in the SF Bay area and decided to take the Bay Tour, which includes some overwater segments.  Just about that time, one of the carb door needle bearings decided to exit its housing and got sucked up into one of the cylinders and welded itself to a spark plug electrode, shorting out that plug.  The change in engine tempo was quite unnerving, being over water and all.  He nursed it back home and when they pulled the plugs to investigate the rough engine, they found the needle bearing.  “Hmmm.  What’s that, where did it come from, and how did it get into the cylinder?”  Needless to say, his carb air box got rebuilt.  

[47U]

  On 11/26/2020 at 12:44 AM, TravelVeteran said:

Mine connects to the front of my cowl. Ram air?  Maybe it’s connected to the wrong thing?

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The duct on the front of the cowl runs to the back of the engine to provide cooling for the mechanical fuel pump.

 

[Jim Peace]

Please please please dont get me started on this topic.....

[carusoam]

Jimmy still has night mares...

1) the hose at the front of the cowl, used to be connected to the generator cooling duct...

if you don’t have a generator any longer... don’t connect the duct to anything other than the alternator, if needed... most don’t.

2) the heat exhaust hose for the carb heat system.... is pseudo modern...65 and older O360s probably didn’t get the heat exhaust hose...

3) if you have a heat exhaust hose... route to the outside... 

4) if your hose is connected to both the front of the cowl, and the back of the heat exhaust... that should ought to mess up a few things related to the heat and the carb heat... So... don’t do that... 

5) What we learned from Jim’s experience... The carb, heat, and carb heat are similar to ancient Jedi technology... it takes a Jedi to be able to work on the system... for some reason.

Great pics from everyone above...

Be sure to get the best layout drawings to make sure you get the proper hose routing...

The system is really designed to last a decade... you guys have done a great job holding it together...

PP thoughts only...

Best regards,

-a-

 

[TravelVeteran]

  On 11/26/2020 at 12:26 AM, 47U said:

Better sit down... It was 10 years ago, but I think .7 or .8 amu at that time.  It comes with the blue-line drawing which contained all the applicable notes.  You get the flapper door, a new shaft, two new (plain) end bearings, the dump valve flapper and its bearing housing.  Even the wire controlling the dump valve position and those connecting terminals were included. 

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Not sure what that means but I called Lasar today and they want almost $1900 for the repair kit. I definitely need the end bearings. Dump valve flapper and housing too probably. 

[carusoam]

Somebody asked what this tube was called...

I gave it the name heat exhaust... hot air gets dumped out that way... when it is not directed towards the carb...

Blue arrow on the drawing...

When you activate the carb heat control... it does two things... closes the heat exhaust butterfly valve, and closes the outside air door going into the intake.... this way, the only air that can enter the carburetor comes from the heat muff...

Common problems of the control of these parts is the wires... if not the proper type of wire... it isn’t stiff enough to push and activate....

The subtle sign I got, that the wire was incorrect... was the bent nail holding it in place...   somewhere around #28 in the drawing...

PP thoughts only, not a mechanic...

-a-

[47U]

  On 11/26/2020 at 4:34 AM, TravelVeteran said:

I called Lasar today and they want almost $1900 for the repair kit.

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Ouch.  You might try searching for the parts on Controller.com.  There’s a pn search feature there and you never know what might turn up in someone’s warehouse.  

Then again, at least LASAR has the parts... and we will all say thank you for helping to keep Mooney open and making parts.  

[TravelVeteran]

repaired my air box and purchased a new duct, selling my old duct (if worth anything) and a replacement air box i didnt use.  if interested feel free to hit me up directly im open to offers. 

http://ebay.us/JajTa1?cmpnId=5338273189

http://ebay.us/BKPQld?cmpnId=5338273189