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Losing air after start, been there!

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draftsjust417(at)gmail.co
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Posted: Sun Apr 09, 2017 7:21 am Post subject: Losing air after start, been there!

Good morning Rich, sorry to gear about your gremlin.

 Very very similar event haopened to me in my CJ6 a few years back; after beautiful start and on taxi out, could visibly watch my air gauge move in the WRONG direction going down. Taxiied back to quiet-as-a-grave hangar while I still had air for brakes. Turning air back on after shutdown and pushing into hangar, listening I found the culprit: a likely-original flex hose in LH main wheel well had a 1" longitudinal rupture from old age, which opened under pressure. I could hear the very gentle hiss and the psi was so low then that it was safe to feel it w/ fingertips. (PLS be careful, feeling for leaks in moderate to high pressure air can be a bloody mistake! Better in this case to listen and use soapy water/spit/piece of paper.)

  Replaced ALL my landing gear hoses (Doug has them), and problem disappeared.  

Maybe this is a place to start the search? 

Best, 

 Justin

 N280NC 

On Apr 9, 2017 9:05 AM, "Rich Langer" <rlanger2(at)comcast.net (rlanger2(at)comcast.net)> wrote: 	  Quote: 	
		  --> Yak-List message posted by: "Rich Langer" <rlanger2(at)comcast.net (rlanger2(at)comcast.net)>

 

 Here is my problem. I open the main air valve and the air pressure holds steady at 36. After pressing the start button, the engine starts normally and for roughly the next few minutes the pressure holds steady at 28. Then the pressure starts to drop and goes to 0 in about 10 minutes.  Emergency air is at 42 and holds steady at 42. I was at Sun-n-fun and there was too much noise to hear any leaks.

 

 Here is what we have checked so far. We checked the fill port for leaks, after we added air from an air tank, with a little spit and no bubbles formed. We pulled the banjo fitting off the air compressor and found the compressor and the banjo fitting were functioning normal. I checked the the snot bottle after the initial start and it was closed. We pulled the pop off valve and it looked normal, spring was good. We pulled the tab on the side of the air start valve and it operated and then closed.

 

 We had no more air, too much noise to hear a leak and ran out of spit.

 

 To recap. No leaks noted after main air valve opened. Main air tank does not refill after engine start and leaks down to 0 after start.  Emergency air has no leaks.

 

 Any ideas of where to look next? Thanks in advance for your expertise.

 

 Rich

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=468174#468174

 

 

 

 

 

 

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hkgibby(at)yahoo.com
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Posted: Sun Apr 09, 2017 10:12 am Post subject: Losing air after start, been there!

Hey Rich-



I would check the three brake system belly valves as possible culprit (QS-1, QS-2 and deposit valve).  Not sure why engine running vs not running makes such a big difference regarding any leak once you open the Main Air valve and are apparently producing air via the compressor...Let us know what you find

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