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Air Leak

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Bill1200

Joined: 19 Oct 2008
Posts: 111
Location: medford oregon

Posted: Tue Feb 03, 2009 9:21 am Post subject: Air Leak

First experience with air leak. First noticed a couple of weeks ago it was bleeding down a little overnight. Called the old owner who thought it was most likely the snot valve lever being out of position, checked it and seemed ok. Then started noticing it would only charge up to about 3 during flight. Yesterday I filled it up at the port and sat in the plane with engine off, air valve closed and could hear a faint leak which sounded like it was coming from behind the pressure guage on the upper left side of the panel. Someone has recommended putting a few drops of oil in the system when doing a external fill, any suggestions on this?

dsavarese0812(at)bellsout
Guest

Posted: Tue Feb 03, 2009 9:38 am Post subject: Air Leak

Bill,

 The snot valve can not cause the main air tank to leak down  unless there is a bad check valve at the right hand side of the "cross" or  manifold where the pressure relief valve is located at the top.

  

 The problem you've described including where you hear the  faint air leak could very well be the pressure relief valve on the  firewall.   If you pressurize the system from the external air fill  port and the pressure will not go up to or hold at approx. 50 ATM's, the  pressure relief valve piston seal or spring or both are probably  bad.

  

 Dennis

  

 [quote]   ---

Bill1200

Joined: 19 Oct 2008
Posts: 111
Location: medford oregon

Posted: Tue Feb 03, 2009 10:39 am Post subject: Re: Air Leak

Thanks Dennis, was talking to Cliff Coy this am, he suggested it might also me the gear selector based on the location of where I think I hear the leak. Will fill the system tomorrow, put the gear selector in neutral and see if it leak stops.  

When I fill from external port I can raise the pressure until the relief valve opens, then the system will slowly bleed down over a couple of days

petervs(at)knology.net
Guest

Posted: Tue Feb 03, 2009 11:06 am Post subject: Air Leak

I agree with Dennis. This is almost always the pressure relief valve.

Sometimes dirt in the seat or just a worn seat. Very easy to replace. Seems

like it has to be replaced about once a year or so.



You can diagnose this by putting about 20 atm in the tank and then soaping

up the relief valve. There is a pair of small holes on the bottom of the

valve that will make bubbles if air is leaking by the seat. 



The last air trouble I had was that sometimes the air pressure would be 20

atm while flying and other times about 45 atm while flying. I went through

everything until finally replacing the relief valve seal, which fixed the

problem. 



Moral... Check the easy stuff first.



Pete



                               

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Bill1200

Joined: 19 Oct 2008
Posts: 111
Location: medford oregon

Posted: Tue Feb 03, 2009 11:48 am Post subject: Re: Air Leak

Thanks

mark.bitterlich(at)navy.m
Guest

Posted: Tue Feb 03, 2009 1:11 pm Post subject: Air Leak

In a YAK-50, if the leak is coming from the Landing Gear handle area,

this is an immediate alert that there is probably an internal leak in a

landing rear actuator cylinder.  Venting air from the cylinders is

through the landing gear selector valve. Hence if one has an internal

leak you will hear air venting from the landing gear selector valve.

Again, in a 50, you can isolate this by putting the landing gear handle

in the middle position which isolates the landing gear system totally

from the rest of the aircraft. You can then pull lines on the cylinders

themselves to determine exactly where the leak is.  



The 52 is much different than the 50 in this regard, with the dual

landing gear handles, etc.,etc.  Dennis, I am sure you can explain the

difference here, because I certainly can not... But I believe that

besides the air relief valve, which Dennis just covered, your leak might

be in the landing gear system if the 52 is close to the 50 in how that

works, which I believe it is.  



Mark Bitterlich

N50YK

  



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dsavarese0812(at)bellsout
Guest

Posted: Tue Feb 03, 2009 4:44 pm Post subject: Air Leak

You are correct Mark.  Air leaking through the gear  handle on a 52 with the handle in down position definitely points to the  possibility of leaking landing gear actuator.  Not too difficult to  diagnose which one.

 Dennis

  

 [quote]   ---

Bill1200

Joined: 19 Oct 2008
Posts: 111
Location: medford oregon

Posted: Wed Feb 04, 2009 2:08 pm Post subject: Re: Air Leak

So today I went to the hangar, pressure had bled down over day and a half to 20atm, filled up to 55atm when relief valve went off, could hear it  bleed down to about 50atm. Went flying for approx 40min with steady decline in pressure to about 30atm, landed with about 20atm after gear,flaps,brakes. Wouldn't come back up past that level sitting at 70% for 2-3 minutes. Shut it down, filled it back up to 50 atm, sprayed soap/water on relief valve didn't see a leak, put gear lever at neutral,checked it 3 hours later looks fairly stable. Will check it again Friday to see if pressure holding with gear lever at neutral.

dsavarese0812(at)bellsout
Guest

Posted: Wed Feb 04, 2009 3:20 pm Post subject: Air Leak

Sounds like it definitely is a leaking gear actuator.  If  it still leaks with the gear handle in the down position, you'll need to isolate  the problem to one of the actuators.

  

 While the gear is down and with the gear handle in the DOWN  position, remove the flex hose B-Nut (17 mm) on the end of the actuator  closest to the chrome shaft that extends and retracts the gear.  (The other  end of the actuator at the top is the DOWN side of the actuator and has 2 flex  lines connected to the shuttle valve).  Now turn on the main air and if air  is coming out of the fitting on the actuator (not the flex hose B-nut), the  seals in that actuator are leaking.  If you've found one bad actuator, you  might as well bite the bullet and remove all of them plus the uplock (parrot  hook) actuators and ship them off to Jill at M14P to be overhauled or buy  the kits from Jill and overhaul them yourself.

  

 Since your going to do all of the actuators, you might as well  remove the flap actuator too.  The condition of one actuator usually  dictates the condition of all of the actuators.

 Dennis

  

  

 [quote]   ---

petervs(at)knology.net
Guest

Posted: Wed Feb 04, 2009 3:21 pm Post subject: Air Leak

Next time put the gear handle in the neutral position while you are flying.

You can try the flap handle too. If that solves the problem then you are

leaking past the seals in one of the cylinders.



If the air is leaking after you close the air valve, it is not the gear

system or flap system because the air valve isolates the tank from those

systems.



Good luck.



Pete



                               

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petervs(at)knology.net
Guest

Posted: Wed Feb 04, 2009 4:00 pm Post subject: Air Leak

And, do this on jacks in case you phuck up.  

     

                                 

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From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of A. Dennis Savarese

 Sent: Wednesday, February 04, 2009 5:16 PM

 To: yak-list(at)matronics.com

 Subject: Re: Re: Air Leak  

  

  

     

Sounds like it definitely is a leaking gear actuator.  If it still leaks with the gear handle in the down position, you'll need to isolate the problem to one of the actuators.  

    

   

    

While the gear is down and with the gear handle in the DOWN position, remove the flex hose B-Nut (17 mm) on the end of the actuator closest to the chrome shaft that extends and retracts the gear.  (The other end of the actuator at the top is the DOWN side of the actuator and has 2 flex lines connected to the shuttle valve).  Now turn on the main air and if air is coming out of the fitting on the actuator (not the flex hose B-nut), the seals in that actuator are leaking.  If you've found one bad actuator, you might as well bite the bullet and remove all of them plus the uplock (parrot hook) actuators and ship them off to Jill at M14P to be overhauled or buy the kits from Jill and overhaul them yourself.  

    

   

    

Since your going to do all of the actuators, you might as well remove the flap actuator too.  The condition of one actuator usually dictates the condition of all of the actuators.  

    

Dennis  

    

   

    

   

   	  Quote: 	
		      

----- Original Message -----   

    

From: Bill1200 (billdykes52(at)gmail.com)   

    

To: yak-list(at)matronics.com (yak-list(at)matronics.com)   

    

Sent: Wednesday, February 04, 2009 4:08 PM  

    

Subject: Re: Air Leak  

    

   

  

--> Yak-List message posted by: "Bill1200" <billdykes52(at)gmail.com (billdykes52(at)gmail.com)>

 

 So today I went to the hangar, pressure had bled down over day and a half to 20atm, filled up to 55atm when relief valve went off, could hear it  bleed down to about 50atm. Went flying for approx 40min with steady decline in pressure to about 30atm, landed with about 20atm after gear,flaps,brakes. Wouldn't come back up past that level sitting at 70% for 2-3 minutes. Shut it down, filled it back up to 50 atm, sprayed soap/water on relief valve didn't see a leak, put gear lever at neutral,checked it 3 hours later looks fairly stable. Will check it again Friday to see if pressure holding with gear lever at neutral.

 

 

 

 

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dsavarese0812(at)bellsout
Guest

Posted: Wed Feb 04, 2009 4:11 pm Post subject: Air Leak

Great suggestion Pete.

 Dennis

  

 [quote]   ---

GreasySideUp

Joined: 24 Oct 2007
Posts: 44

Posted: Wed Feb 04, 2009 4:29 pm Post subject: Re: Air Leak

 	  petervs(at)knology.net wrote: 	
		  I agree with Dennis. This is almost always the pressure relief valve.

Sometimes dirt in the seat or just a worn seat. Very easy to replace. Seems

like it has to be replaced about once a year or so.



You can diagnose this by putting about 20 atm in the tank and then soaping

up the relief valve. There is a pair of small holes on the bottom of the

valve that will make bubbles if air is leaking by the seat. 



The last air trouble I had was that sometimes the air pressure would be 20

atm while flying and other times about 45 atm while flying. I went through

everything until finally replacing the relief valve seal, which fixed the

problem. 



Moral... Check the easy stuff first.



Pete



                               

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I think this is my problem.  Over the winter it now bleeds down to about 15 when I fill externally.  Where do I get those relief valve seals from?  Should I replace the spring and any other internals as well?

petervs(at)knology.net
Guest

Posted: Wed Feb 04, 2009 7:33 pm Post subject: Air Leak

Here is how I repair this...



Jill has the seals. I've made them myself out of a sheet of nitrile, but

they don't last as long as the one's Jill sells. Her's are out of a harder

rubber.



Basically you unwire, loosen the jam nut and unscrew the top of the relief

valve. Count how many turns it takes to remove it so you can get it at

approximately the same setting when you reassemble. Be careful to go slow at

the end if there is any pressure left in the system or you'll blow the valve

guts across the hanger. Some people like to actuate the flaps and brakes

until the air is gone, but I just unscrew the valve top slowly. Once you

have the parts in hand you can pry out the rubber disk in the bottom of the

brass actuator. If your pressure was ok when your engine was operating and

consistent, you probably don't need to replace anything but the rubber disk.

Clean everything until it is like new, dirt here causes problems. Especially

clean the seat in the bottom of the valve body. Spraying brake parts cleaner

on a q-tip and swabbing out the seat works good. Press the rubber disk in

the brass actuator. Some people like to glue it in place, but I don't and

have never had a problem. If you just press it in and you are somewhere and

it fails, you can take it apart and flip the rubber disk over and be back in

business. Coat everything with air tool oil and reassemble. Fill the system

with air watching the gauges carefully. If you get to 45 or 50 you need to

loosen the top of the relief valve until it is hissing good. Then add air

again until it pops. If you add air too slow it will only hiss, but it you

let the air in fast the valve your make a machine gun sound. Personally I

set my air so that it pops at 45 and bleeds down and stabilizes at 40. Many

guys run their air up at 55, but I think that higher pressure just wears out

the pump and parts faster. If your plane is easy to start, 40 is plenty. My

plane will start reliably down to 25 unless it is sooooper cold.



Good luck,



Pete



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nc69666(at)aol.com
Guest

Posted: Thu Feb 05, 2009 12:29 am Post subject: Air Leak

I recently had the same symptoms on my CJ, it turned out to be a leaking air hose on the up side of the landing gear, was leaking thru the wall of the hose, hoses were getting along in life so replaced all hoises on the airplane.. No more leak..    Gary..  CJ .... N22YK

 

 

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dsavarese0812(at)bellsout
Guest

Posted: Thu Feb 05, 2009 5:32 am Post subject: Air Leak

I would recommend contacting Cliff Coy at Gesoco.  Cliff  usually has new pop-off valve pistons with the seals.  Around $50 and  well worth replacing with a new piston.  Even the seals that Jill sells,  which are good, do not last nearly as long as the new piston w/seal  will.

 Dennis

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