Factory Oxygen Leaking when "off"

[Boilermonkey]

Our factory Oxygen system has a slow leak (25psi a day) when the control knob is turned to off.  Our A&P can't find the leak.  We ran it up to about 1250 PSI and he sprayed stuff to look for bubbles.   Our next step is to run it up to 2000 PSI....but looking for other tips.  

I would assume that the leak would be isolated to the filling port, path to to pressure gauge in the cabin, or to the tank coupling.

Any ideas of how to track the leak down.

[buddy]

I have the same problem, I replaced the fill port and ran a new line from the fill port to the tee with new fittings because I could not see well enough if the connection was leaking down around the fill port. I also pulled the seats out so I could pull the panel up far enough to spray around the gauge and the fitting at the gauge but didn’t  see any bubbles. You may want to try replacing the O ring on the fill line that goes into the tank regulator. The only thing I wasn’t able to do was to make sure that the boys at the factory didn’t put a splice in the line that runs from the tee to the gauge.

So for now I just loosen the fill line (the one with the O ring) at the regulator until it pulls out of the regulator far enough to stop the O2 from leaking out and I use the cannulas will an altitude compensating gauge with a floating ball that tells me the O2 is still flowing from the tank to the cannulas. The problem with this is you will have to tighten the supply line fitting at the regulator to check the psi in the tank by looking at the gauge in the cabin.

If you want PM me with your number and I may be able to explain it a little better.

[LANCECASPER]

6 hours ago, Boilermonkey said:

Our factory Oxygen system has a slow leak (25psi a day) when the control knob is turned to off.  Our A&P can't find the leak.  We ran it up to about 1250 PSI and he sprayed stuff to look for bubbles.   Our next step is to run it up to 2000 PSI....but looking for other tips.  

I would assume that the leak would be isolated to the filling port, path to to pressure gauge in the cabin, or to the tank coupling.

Any ideas of how to track the leak down.

Has the left interior panel recently been taken off? Sometimes when that happens the Swagelok fitting going into the cabin O2 gauge develops a leak.

[tls pilot]

Not sure of your field elevation?

The O2 regulator usually will not allow oxygen flow until 8-9000 ft

If on the ground interior knob turned on and cannula or mask connected, it should not flow if at an airport near sea level

Look at the filler port, regulator, or bottle

Has the regulator been checked lately?

[Boilermonkey]

Bottle and regulator replaced already.  Will take a look at the O ring next.  Thanks gents.

[buddy]

The small “O” ring should also be lubricated with a lube compatible with oxygen.

[FoxMike]

O2 leaks are hard to find.  When the control knob is in the off position the control cable may not be moving quite far enough to shut the regulator off.  The control cable probably could use lubrication and if the bottle was replaced the cable at the bottle end may not have been reinstalled per spec.  Check to be sure the the lever on the regulator is all the way closed.

[carusoam]

There are a few threads about finding O2 leaks around here…

Search the word “snoop” for the really tough ones….

This is a leak detection fluid made by one of the O2 system manufacturers…

Best regards,

-a-

[cbogie]

On 10/30/2021 at 6:06 PM, tls pilot said:

Not sure of your field elevation?

The O2 regulator usually will not allow oxygen flow until 8-9000 ft

If on the ground interior knob turned on and cannula or mask connected, it should not flow if at an airport near sea level

Look at the filler port, regulator, or bottle

Has the regulator been checked lately?

Don’t have my POH handy , but this is not my experience.  Mine flows just fine at field elevation of 1275.   It’s how I check it before launching into the rarefied blue yonder.  

[Boilermonkey]

Following up.  The fitting for the cabin O2 gauge needed to be replaced.   She hold pressure just fine!  Took her up to 14K to see how well it was regulating and it was fine.   Soon I'll have the rebuilt engine and a practically new airplane.

[LANCECASPER]

4 hours ago, Boilermonkey said:

Following up.  The fitting for the cabin O2 gauge needed to be replaced.   She hold pressure just fine!  Took her up to 14K to see how well it was regulating and it was fine.   Soon I'll have the rebuilt engine and a practically new airplane.

If you or your avionics installer has had that left side panel off there’s a good chance that the Swagelok fitting loosens on the gauge just by looking at it.

[Mark Cline]

10 hours ago, cbogie said:

Don’t have my POH handy , but this is not my experience.  Mine flows just fine at field elevation of 1275.   It’s how I check it before launching into the rarefied blue yonder.  

Not my experience either.  My oxygen flows at a field elevation of 2120 ft.  Thats also one of my checks before going up high.  I had an oxygen leak that ended up being a problem with the wire connection to the mechanism behind the knob.  

[Healthpilot]

On 12/18/2021 at 6:21 AM, Boilermonkey said:

Following up.  The fitting for the cabin O2 gauge needed to be replaced.   She hold pressure just fine!  Took her up to 14K to see how well it was regulating and it was fine.   Soon I'll have the rebuilt engine and a practically new airplane.

I just had my bottle replaced and I have the same problem. Did you have to spray to see this leak? How did you find the culprit?

[Boilermonkey]

They sprayed and could not find it at 1000 psi.  They did at 1700.

[Ed de C.]

I thought I'd add my recent experience to this thread.  My 2008 Ovation is new to me as of 9 months ago and we missed oxygen leaks at the pre-buy.  Reason is that the pre-buy shop focused on the expired tank and once it was back in did not have time to catch what turned out to be 2 leaks.  

A few months later, I suspected a leak based on periodic gage readings.  I had the tank filled to 1,800 psi and started charting the pressure over time.  It was down to 1,200 over 30 days.  The shop did the easy part first which as to open the avionics access panel in the rear fuselage and spray bubble solution around.  They found leak number one at a T fitting.  They tightened that up and the leak stopped.  They recharged the system and yet I continued to notice pressure loss. 

A month later when we had the interior out for CIES fuel senders install, the shop checked for leaks at the pressure gage fitting and found the second one.  They tightened that one up.  Pressure has held steady at 1,800 for two months now (up and down slightly for temperature changes).  

It feels good to clean up a squawk.  

Best,

Ed

[kortopates]

Glad to hear you got it fixed. I don't know of any pre-buy inspection checklist that would look for O2 leaks - unless its a big obvious leak that would be apparent while in the shop. Nor its on the annual inspection checklist. Its not something that is discovered by mechanics but an owner that its following their O2 psi over time. Afterall, O2 leaks are to find so spending the $ on a cursory inspection may not even be effective without any suspicion of a leak.

Pre-buy items are for big $ items that effect your price negotiations, recognizing we're buying a used aircraft.