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Losing Air After Start

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Rich Langer

Joined: 10 Apr 2007
Posts: 26
Location: Florida

Posted: Sun Apr 09, 2017 4:58 am Post subject: Losing Air After Start

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

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dsavarese0812(at)bellsout
Guest

Posted: Sun Apr 09, 2017 5:17 am Post subject: Losing Air After Start

Rich,

As we discussed at S&F, the air start valve itself could be leaking 

after it opens when you start the engine. Other than the air start 

valve, if you have an actuator leaking, you should be able to hear air 

leaking from the gear selector in the front cockpit.  But you probably 

need to be in a much quieter place than the S&F flight line to hear any 

air leaking.



If the air start valve iscausing the leak down, the compressor most 

likely will not be able to keep up with the leak.   If the main air tank 

is not leaking down with the main air valve closed, thatindicates the 

leak is after the main air valve.  ie: air start valve, actuators (gear, 

flaps, uplock), air hose between the firewall and the air start valve.



Dennis



A. Dennis Savarese

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1



On 4/9/2017 8:58 AM, Rich Langer wrote:

 	  Quote: 	
		   



 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





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

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SVA402

Joined: 13 Jan 2017
Posts: 5

Posted: Sun Apr 16, 2017 9:20 pm Post subject: Re: Losing Air After Start

Hi Rich, I had this problem recently and it turned out to be the other snot valve in the belly. It was cracked open just barely and kept bleeding pressure off. I ended up having to shut it with channel locks to get it tight enough. I need to rebuild or replace it but it solved the problem for now.

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woodja51

Joined: 13 May 2015
Posts: 40
Location: MELBOURNE AUSTRALIA

Posted: Sun Apr 23, 2017 11:42 pm Post subject: Re: Losing Air After Start

If the snot valves are the cause , check that the springs are still on them .. assuming they are in good condition...

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Rich Langer

Joined: 10 Apr 2007
Posts: 26
Location: Florida

Posted: Sun Jun 25, 2017 5:01 am Post subject: Re: Losing Air After Start

Just to update my "losing air after start" problem, eventually, we found the problem to be a hole in my right brake expander tube. That was the last place I would have guessed to be the problem because I have not heard of one leaking.  I replaced the whole brake assembly because of  inter-granular corrosion in one of the metal disc's. Thanks to Dennis , Doug, Craig, Pappy, and Charley for all the help and advice. You guys are awesome.

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jblake207(at)comcast.net
Guest

Posted: Mon Jun 26, 2017 6:18 am Post subject: Losing Air After Start

Rich,

  

 Glad you found the problem and got it repaired.  Good thing the smart guys were there to give help and advice, but what about the rest of us?  Those of us who stood around scratching our heads and uttering over and over "Well, Rich, I don't know... I just don't know."  Don't we get any credit? - see attached.  



  

 See you in  a couple of weeks my friend!

  

 JB

 



   From: "Rich Langer" <rlanger2(at)comcast.net>

To: yak-list(at)matronics.com

Sent: Sunday, June 25, 2017 8:01:35 AM

Subject: Re: Losing Air After Start

 



--> Yak-List message posted by: "Rich Langer" <rlanger2(at)comcast.net>

 



Just to update my "losing air after start" problem, eventually, we found the problem to be a hole in my right brake expander tube. That was the last place I would have guessed to be the problem because I have not heard of one leaking.  I replaced the whole brake assembly because of  inter-granular corrosion in one of the metal disc's. Thanks to Dennis , Doug, Craig, Pappy, and Charley for all the help and advice. You guys are awesome.

 

 

Read this topic online here:

 



http://forums.matronics.com/viewtopic.php?p=470456#470456

 

 

                      &nbs=================

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Clouddog

Joined: 02 Jun 2016
Posts: 117
Location: Lebanon, TN

Posted: Mon Jun 26, 2017 12:42 pm Post subject: Losing Air After Start

Rich, glad you found the problem. See you at the Music City Mingle in a couple of weekends!



Greg Wrobel

On Jun 25, 2017 9:07 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)>

 

 Just to update my "losing air after start" problem, eventually, we found the problem to be a hole in my right brake expander tube. That was the last place I would have guessed to be the problem because I have not heard of one leaking.  I replaced the whole brake assembly because of  inter-granular corrosion in one of the metal disc's. Thanks to Dennis , Doug, Craig, Pappy, and Charley for all the help and advice. You guys are awesome.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=470456#470456

 

 

 

 

 

 

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