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Pop-off valve

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john_graham

Joined: 09 Aug 2007
Posts: 45
Location: Algonquin, IL

Posted: Fri Jul 04, 2008 12:23 pm Post subject: Pop-off valve

Happy Fourth of July!  I am having an issue with my pop-off valve.  If I leave the snot valve in during cruise, the main air pressure climbs to over 8 on the scale (80 ATMs).  If I cruise with the snot open, it will not climb much above 5.  When I land and it is at 8, the pop-off valve slowly hisses for an hour or more and slowly reduces to about 4.5.  The snot valve does GUSH air when opened after cruise if it has been left in (i.e., it works). 

  

I disassembled the pop-off valve on the firewall and removed the spring - looked fine, but I am not sure if it is the right one and have no idea how to verify if it is the correct size spring.  Also, there were 3 little round washers at the bottom of the spring - almost as if they were in there for spacing purposes.  Is this normal? 

  

So...I am at a loss as to what to do.  We have tried to adjust the nut on the pop-off valve but can't seem to dial it in to pop at the right pressure (I presume the optimal pressure to pop would be 5.5).   

  

Any ideas?



John P. Graham

CubFlyer1940(at)Yahoo.com

Cell phone (630) 390-9451

           [quote][b]

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_________________
John Graham
N15YK 1993 Yak-52
CubFlyer1940@Yahoo.com
(847) 641-1330

randmyak52(at)bellsouth.n
Guest

Posted: Fri Jul 04, 2008 2:01 pm Post subject: Pop-off valve

John:

   I would be concerned about the pressure building to  8. assuming the gauge is correct, you are building pressure to some 1,175 PSI.  Too much for the system. You are correct that Approx. 5.5 is the ideal  pressure.There should be no washers in the release valve, apparently someone has  added those. I would not be concerned if I could maintain 4.5 after leakdown as  this is enough air for a start. Try it with some of the washers removed. If you  can maintain enough air, go with that.

  

                                                                                                                                                                      Robert

 [quote]   ---

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dsavarese0812(at)bellsout
Guest

Posted: Fri Jul 04, 2008 3:35 pm Post subject: Pop-off valve

John,

 There should not be any washers/spacers inside the pop off  valve.  Typically when someone installs them, it's because they could not  get enough spring tension on the piston to bring the pressure above 50  ATM's.  You should probably replace the pop off valve piston or at  least the piston seal, available from M14P, Inc.  As Jill if they have a  correct spring.  Then reinstall the spring without the washers/spacers and  adjust to 55 ATM's pop off point.  It should bleed down to about 50 ATM's  once it shuts down.

 Dennis

   

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wlannon(at)persona.ca
Guest

Posted: Fri Jul 04, 2008 8:07 pm Post subject: Pop-off valve

I find it hard to believe what I am reading here!   80 ATM?? 

 Do you not have any manuals for your aircraft?  The system TEST pressure is 75 ATM. The operational limit is 50  ATM.

 Your pressure relief valve is obviously in terrible  condition. There should be no washers, these were no doubt added by someone who  either has no idea how the system works or was too cheap to buy a new  valve plunger or, more likely, both.

 I assume you are flying a Yak52 where the emergency  tank is not charged by the compressor. If that is the case you are safe to set  the relief pressure at a maximum of 50 ATM.  If it is a CJ6 you should set  to a maximum of 45 ATM as you will find the emergency pressure creeping up  another 5 ATM. 

 All of this assumes of course that you have a  serviceable relief valve. 

 At the very least you need a new valve plunger  preferably with a new spring and quite possibly a new valve body. 

 Doug Sapp has all of these in stock for the  CJ.  Whether they fit the 52 I don't know but if not I'm sure George  Coy or Jill can help you.

  

 Walt  

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yakplt(at)yahoo.com
Guest

Posted: Sat Jul 05, 2008 1:59 pm Post subject: Pop-off valve

The CJ vave Doug sells will not fit into 52's or 50's AS IS.  However, the internal plunger and spring will fit PERFECTLY as replacements for the valve already in the aircraft.  Make sure to replace them both as a pair.   

  

A few comments.   

  

1. It is amazing his main tank did not blow.   

  

2.  How in the world did it pressurize at all with the snot valve open?   

  

Some things here do not sound right.   

  

I would advise emptying all air and then using external air with a known good gage to repressurize and make sure your aircraft gage is reading correctly.  

  

There is no question that the spring with washers deal with another case of some home brew repair made by someone less than bright.  Don't be surprised, that kind of thing happens all the time.   

  

Mark Bitterlich 



 

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viperdoc(at)mindspring.co
Guest

Posted: Sun Jul 06, 2008 7:02 pm Post subject: Pop-off valve

Better yet buy a new pop off valve from Gill or Steve Culp. At the least get a new piston, seal and spring from Jill. George Coy also has them.  

I don’t think I would put the washers in ever. You are lucky the tank did not let go.  

Doc  

       

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Robert Langford

 Sent: Friday, July 04, 2008 4:57 PM

 To: yak-list(at)matronics.com

 Subject: Re: Pop-off valve  

  

  

     

John:  

    

  I would be concerned about the pressure building to 8. assuming the gauge is correct, you are building pressure to some 1,175 PSI. Too much for the system. You are correct that Approx. 5.5 is the ideal pressure.There should be no washers in the release valve, apparently someone has added those. I would not be concerned if I could maintain 4.5 after leakdown as this is enough air for a start. Try it with some of the washers removed. If you can maintain enough air, go with that.  

    

   

    

                                                                                                                                                                    Robert  

   	  Quote: 	
		      

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

    

From: John Graham (cubflyer1940(at)yahoo.com)   

    

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

    

Sent: Friday, July 04, 2008 3:20 PM  

    

Subject: Pop-off valve  

    

   

          

Happy Fourth of July!  I am having an issue with my pop-off   valve.  If I leave the snot valve in during cruise, the main air   pressure climbs to over 8 on the scale (80 ATMs).  If I cruise with the   snot open, it will not climb much above 5.  When I land and it is at 8,   the pop-off valve slowly hisses for an hour or more and slowly reduces to   about 4.5.  The snot valve does GUSH air when opened after cruise if it   has been left in (i.e., it works).   

    

I disassembled the pop-off valve on the firewall and removed the spring -   looked fine, but I am not sure if it is the right one and have no idea how to   verify if it is the correct size spring.  Also, there were 3 little   round washers at the bottom of the spring - almost as if they were in there   for spacing purposes.  Is this normal?   

    

So...I am at a loss as to what to do.  We have tried to adjust the   nut on the pop-off valve but can't seem to dial it in to pop at the right   pressure (I presume the optimal pressure to pop would be 5.5).     

    

Any ideas?

   

   John P. Graham

   CubFlyer1940(at)Yahoo.com

   Cell phone (630) 390-9451        

    	  Quote: 	
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7/3/2008 7:19 PM   	
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       [quote][b]

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ronwasson

Joined: 05 Sep 2007
Posts: 30

Posted: Mon Jul 07, 2008 12:53 pm Post subject: Pop-off valve

Anyone have a pop valve body for  a 52. Friend has a cracked one with  

good internal parts.  Jill does not not have one.

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dougsappllc(at)gmail.com
Guest

Posted: Mon Jul 07, 2008 1:13 pm Post subject: Pop-off valve

Ron and other 52 drivers,

 Mike and I have been brain storming this problem and think we have found a simple way to adapt the CJ6 pop off valve assy and check valves to the Yak 52. Parts are going out to Mike today.  Stay tuned, Mike or I will post the results as soon as he has done the install. 

   

  

 



 

 On Mon, Jul 7, 2008 at 1:49 PM, ronald wasson <ronwasson(at)mindspring.com (ronwasson(at)mindspring.com)> wrote:

 [quote]--> Yak-List message posted by: ronald wasson <ronwasson(at)mindspring.com (ronwasson(at)mindspring.com)>

 

Anyone have a pop valve body for  a 52. Friend has a cracked one with good internal parts.  Jill does not not have one.   

 

-- 

Always Yakin,

Doug Sapp

Phone 509-826-4610

Fax 509-826-3644   [quote][b]

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