337 Oxygen Leak

I am a retired 747 captain and have been restoring a T337C for seven years. The restoration is nearing completion and I need to find and stop a slow high pressure oxygen leak. I have bubbled with soap solution all connections many times and found no leaks. Then I repeated the process on all connections with Leak-Tec, again found no leaks.

Does anyone know of a leak detector system or process (probably electronic) that might pick up this small oxygen leak? Or does anyone have any other suggestion on how I should proceed. I hate to install a new headliner without solving this problem first.

Thanks,
Jim Hatfield

[Bob Cook]

Jim

There are numerous methods of detecting a leak.
one method ::
small charge of freon and use a freon detector... very sensitive.
be sure to purge the system using a vacuum then recharge with oxygen after the leak is found.

Is this the large tanks in the overhead? If so then why not consider a small bottle like skyox which is cheaper to fill, easy to certify and far less weight. The overhead oxygen system with dual tanks must be robbing you of at least 100 lbs of payload. I can look it up if you like or look at the original equipement list.

You may need to get these tanks properly pressure tested as I would question putting 2500 psi to them without doing so. They can be very good missiles when they blow....... think less than every 10 yrs. they do a under water static test and no doubt will find your leak if it is in the tank..

Probably came out of a 747 <G>. like to fly those "7's" ??

Bob

[Kim Geyer]

Jim
If you haven't had your bottles hydrostatic tested you should do so as a lot of FBO's won't service bottles that are out of date.
Your bottles are probably due every 5 years.
The cessna manual says overhaul the regulator at this time along with resealing the filler valve and putting new o-rings in all the plug-in fittings. as for leaks, the guage could have an internal leak or the regulator is not shutting off all the way
Hope this helps
Kim

Thanks for the tip on using a freon charge and detector. That will be the next step and we'll pump the system down to clear it.
HRD Aero sys in valencia, Ca. hydro tested and leak checked both bottles an the regulator. I also resealed the filler check valve and all six outlets per the manual. I've increased weight with serious efforts insulating the cabin and I'll be weighing the aircraft soon. I hope to still have a decent 4 place zero fuel weight. Thanks again Bob.

Jim

Thanks, Kim. I should have included your name in my last message. I appreciate your help. HRD company also checked the guage for me. I will let you know how it turns out.

Thanks Again
Jim

[rick bell]

my 73 p337 was always leaking and we never could find the source. finally my mechanic looked at the shut off valve and the labeling was wrong (off was on). changed the label and the ox tanks quit bleeding off. when the valve is on they tend to leak very slightly and will empty the tank in a day or so.