tracking down o2 system leaks

[peevee]

our onboard O2 is leaking with the valve off.

I don't even know where to begin with this one. Are there any common points to check? Bad shutoff valve maybe? It's a little sticky to shut off, when you slide the lever to open you can hear it pop as it pressurizes, when you close it you have to close it and then push on it again to get it to shut off (you can hear it hiss for a second when you do) but it seems like the valve is getting pushed all the way off.

[DonMuncy]

First thing to check is to make sure the valve is shutting off. Push the lever in the cabin. Then open the panel on the plane and see if you can move the valve lever any further by hand. If the valve shuts off completely, and still loses pressure, it is the valve leaking. Only other choice would be a tank leak. (Extremely unlikely)

[peevee]

The tank was sent out for a pressure check this fall, any chance they didn't get the valve tight to the tank? 

Does anyone repair the valves or is it a replace only kind of deal? 

 

Since it's a little finicky on shut off I guess the logical answer is it isn't shutting off quite completely. 

 

Thanks don

Edited January 14, 2017 by peevee

[DVA]

Put a little slightly soapy water on a cloth and wet down the area around the valve and the neck of the bottle - look for bubbles.

[kortopates]

Regulators can be rebuilt/repaired/overhauled- but it's very unlikely that's the problem. Don is most likely right but that is extremely common; especially after the tank is re-installed.
It's also very easy to test for. After a period of time with it off, plug a cannula into a port. If you feel any pressure and hear any gas leaking as you plug it in you just found the leak. Next see if you can get it to shut off completely by just pushing the lever further/harder to off. If that fixes it then you just need to correct the cable rigging so it's pushing it closed in the off. That's the cause 99% of the time.
For finding high pressure leaks brush or spray O2 leak detection fluid on every connection, port and seem were the regulator screws on to the tank. Don't forget the servicing portal from where the Scott adapter screw on to the O2 port.
Bottom line, no wrenching till you find the leak. You'll find it.


Sent from my iPhone using Tapatalk

[carusoam]

Liquid snoop...

http://www.scottecatalog.com/equipspc.nsf/24c78b07bd0fb8cc8525696100417fc4/3b74fa0d8cb9ff3a8525686b00691378?OpenDocument

Sounded like something I could look up.  I have no O₂ experience, yet....

Best regards,

-a-

[peevee]

22 minutes ago, kortopates said:

Regulators can be rebuilt/repaired/overhauled- but it's very unlikely that's the problem. Don is most likely right but that is extremely common; especially after the tank is re-installed.
It's also very easy to test for. After a period of time with it off, plug a cannula into a port. If you feel any pressure and hear any gas leaking as you plug it in you just found the leak. Next see if you can get it to shut off completely by just pushing the lever further/harder to off. If that fixes it then you just need to correct the cable rigging so it's pushing it closed in the off. That's the cause 99% of the time.
For finding high pressure leaks brush or spray O2 leak detection fluid on every connection, port and seem were the regulator screws on to the tank. Don't forget the servicing portal from where the Scott adapter screw on to the O2 port.
Bottom line, no wrenching till you find the leak. You'll find it.


Sent from my iPhone using Tapatalk

They make o2 leak detection fluid? Sweet! I bet you're right, the rigging. I'll mess with it when it warms up. 

 

Any recommendations for overhaul shop on the valve if it comes to it? 

Edited January 14, 2017 by peevee

[buddy]

I just went though the same problem believe it or not in my M20R. The first thing I did was to make sure the valve shuts off completely so loosen up the connection on the cable and make sure it is completely shut off which it sounds like you did. Second try spaying leak detection fluid around all the connections you can find, you can use Joy soap to do this. Make sure all the connections are tight. My problem was the same as yours I lost O2 with the valve shut off. I found a bad O ring (which didn't look bad) in the supply line to the tank. You can easily remove this line, it is the small line that comes off a "T" and runs to the O2 tank, this line also feeds your gauge and is connected to your outside fill port. Remove the fitting on the tank first this will allow the O2 not to leak out of the tank then remove the fitting on the "T". The small O ring is on the end that was connected to your tank. Make sure that when you replace the O ring it can be used with oxygen. If you have any questions PM me with your number and I will give you a call and walk you through it.

[DonMuncy]

37 minutes ago, kortopates said:

Regulators can be rebuilt/repaired/overhauled- but it's very unlikely that's the problem. Don is most likely right but that is extremely common; especially after the tank is re-installed.
It's also very easy to test for. After a period of time with it off, plug a cannula into a port. If you feel any pressure and hear any gas leaking as you plug it in you just found the leak. Next see if you can get it to shut off completely by just pushing the lever further/harder to off. If that fixes it then you just need to correct the cable rigging so it's pushing it closed in the off. That's the cause 99% of the time.
For finding high pressure leaks brush or spray O2 leak detection fluid on every connection, port and seem were the regulator screws on to the tank. Don't forget the servicing portal from where the Scott adapter screw on to the O2 port.
Bottom line, no wrenching till you find the leak. You'll find it.


Sent from my iPhone using Tapatalk

The factory "cable" is not very good. It works great for "pulling", but when pushing (turning off), the inner wire bends between the end of the outer cable and the lever on the regulator. The good cure is to replace the cable with the net larger size wire. No more problems.

[Danb]

Don I've been going through this, my valve didn't shut off fully and the cable would not stay attached to the back of the control in the plane, we made sure it was off fully at the bottle when closed. then drilled a hole in the cable and secured it to the back of the on off control in the plane with a lock washer, the fix was a week ago  it has not leaked yet although only a week. The way Mooney has set this up is quite  flimsy at best. 

[peevee]

45 minutes ago, buddy said:

I just went though the same problem believe it or not in my M20R. The first thing I did was to make sure the valve shuts off completely so loosen up the connection on the cable and make sure it is completely shut off which it sounds like you did. Second try spaying leak detection fluid around all the connections you can find, you can use Joy soap to do this. Make sure all the connections are tight. My problem was the same as yours I lost O2 with the valve shut off. I found a bad O ring (which didn't look bad) in the supply line to the tank. You can easily remove this line, it is the small line that comes off a "T" and runs to the O2 tank, this line also feeds your gauge and is connected to your outside fill port. Remove the fitting on the tank first this will allow the O2 not to leak out of the tank then remove the fitting on the "T". The small O ring is on the end that was connected to your tank. Make sure that when you replace the O ring it can be used with oxygen. If you have any questions PM me with your number and I will give you a call and walk you through it.

Thanks! Another good possibility, do you remember the oring specs? It might be different on your r vs our k

[DonMuncy]

18 minutes ago, Danb said:

Don I've been going through this, my valve didn't shut off fully and the cable would not stay attached to the back of the control in the plane, we made sure it was off fully at the bottle when closed. then drilled a hole in the cable and secured it to the back of the on off control in the plane with a lock washer, the fix was a week ago  it has not leaked yet although only a week. The way Mooney has set this up is quite  flimsy at best. 

I'm not sure I understand what you did. Do you have photos, sketch etc. Glad it worked anyway.

[buddy]

My mechanic supplied the O ring, it was a small one. Again if you want to PM me with your number I'll give you a call, I'm pretty familiar with the system.

[peevee]

18 minutes ago, buddy said:

My mechanic supplied the O ring, it was a small one. Again if you want to PM me with your number I'll give you a call, I'm pretty familiar with the system.

Thanks! Let me dig into it a little so I have a clue what I'm talking about first. It's hard for me to get at that valve, I'm a little big to fit in the avionics bay

Edited January 14, 2017 by peevee

[kortopates]

6 hours ago, Danb said:

Don I've been going through this, my valve didn't shut off fully and the cable would not stay attached to the back of the control in the plane, we made sure it was off fully at the bottle when closed. then drilled a hole in the cable and secured it to the back of the on off control in the plane with a lock washer, the fix was a week ago  it has not leaked yet although only a week. The way Mooney has set this up is quite  flimsy at best. 

Are you sure you aren't missing parts that got left off from previous bottle R&R? Did you check the IPC to make sure? What you describe really sounds like it didn't entirely go back together right since the cable is normally well secured i.e. not really flimsy. 

Edited January 15, 2017 by kortopates

[kortopates]

 

21 hours ago, peevee said:

They make o2 leak detection fluid? Sweet! I bet you're right, the rigging. I'll mess with it when it warms up. 

 

Any recommendations for overhaul shop on the valve if it comes to it? 

This repair station specializes in O2 equipment and is very good. I really doubt that will be your problem, but easy enough to tell.

 

20 hours ago, peevee said:

Thanks! Let me dig into it a little so I have a clue what I'm talking about first. It's hard for me to get at that valve, I'm a little big to fit in the avionics bay

This is the little o-ring on the high pressure connection to the regulator - its a MS28775-006. This should be replaced every time the bottle is R&R'd and therefore shouldn't leak unless it was damaged on the install and thus leaking from the start.  

 

oops- I see the repair station didn't get included above as intended - this is it:

http://www.c-l-aero.com/

 

Edited January 15, 2017 by kortopates

[Yooper Rocketman]

On 1/14/2017 at 2:40 PM, DonMuncy said:

The factory "cable" is not very good. It works great for "pulling", but when pushing (turning off), the inner wire bends between the end of the outer cable and the lever on the regulator. The good cure is to replace the cable with the net larger size wire. No more problems.

Another option is to install a spring to aid the cable when "pushing" because, as Don notes" the inner cable is too small/flimsy when pushing with the resistance of valve.  When the cable "pulls" the extra resistance of the spring is easily overcome.  I did that on mine and it has worked great ever since (6-7 years ago).  

Definately check "all" connections for leaks, not just at the valve. I had a leak on one of the small copper lines after servicing the O2 tank.  

Tom

[DonMuncy]

 

I think I misspoke in an earlier post. I said if the regulator valve was shutting off, and still losing pressure, it had to be a tank leak. I forgot about the filling valve. It is on the high pressure side of the regulator, and could be leaking. Try not to let it be that. That valve costs about $300.

[carusoam]

Reminds me of a an economics lesson regarding reactively lowering interest rates while trying to control an out of control unemployment rate...  it was considered being like 'pushing on a string'.  Not very effective...

If the control wire is flimsy, it will be challenged flopping the valve at the end...

Another Mooney based challenge of a similar sort... The C has a wire that controls the carb heat butterfly valve.  Some age and a bit of corrosion and the butterfly valve doesn't fully operate either...

Hows that for almost staying on topic?  

Best regards,

-a-

[peevee]

If I don't isolate the leak to something else a helper spring might be a good option if I can figure out a way, thanks 

[carusoam]

Consider the challenge...

1) a helper spring could help close the valve when you want it open...

2) this might trade a problem you have, for one you don't want, even more...

Sounds like an engineering design dilemna.

Best regards,

-a-

Edited January 16, 2017 by carusoam

[Yooper Rocketman]

3 hours ago, peevee said:

If I don't isolate the leak to something else a helper spring might be a good option if I can figure out a way, thanks 

You could install it at either end of the cable, in the cockpit at the control linkage (under the upholstery) or at the rear by the O2 tank.

2 hours ago, carusoam said:

Consider the challenge...

1) a helper spring could help close the valve when you want it open...

2) this might trade a problem you have, for one you don't want, even more...

Sounds like an engineering design dilemna.

Best regards,

-a-

If you use a light spring, there is no issue.  With the over center action on both ends of the cable, the spring will never move the cable on it's own unless you have selected one with too much tension.

Tom

Edited January 16, 2017 by Yooper Rocketman

[Danb]

On January 14, 2017 at 4:24 PM, DonMuncy said:

I'm not sure I understand what you did. Do you have photos, sketch etc. Glad it worked anyway.

Don as you well may know I'm  mechanically challenged, I pulled my invoice from my  MSC it says removed forward seats, disconnected left sidewall panel, removed the oxygen control from the plane, drilled a hole in pin and installed cotter pin to act as cable retainer.  Prior to the fix the cable would not stay on the oxygen control behind the panel. It works now.

[DonMuncy]

OK. He is talking about the front end of the cable. I thought it was on the other end. Thanks

[Danb]

Yep