propane leak

[Safari64]

I have a Therm'x propane catalytic heater in my '64 Safari. It has a very slight propane leak detected with spray on 'bubble" leak detector.

Very faint stream of bubbles comes from bottom of main banjo connector from feed line. The joint has been taken apart, cleaned, surfaced and it still has faint leak in same spot.

This has old style copper banjo/tubing connectors not used anymore (for a reason). Even worse, it’s metric! It has aluminum washer, brass/copper tubing banjo, 2nd aluminum washer mounted with pass through bolt to aluminum valve body.

How can I seal the connection?

Thread seal on outside of connection didn't work. Leaks same spot. Extremely faint but a propane leak is a propane leak. It only leaks when heater valve is on. This is not a joint I ever plan to take apart again, but would like to keep the original heater intact, leak free. Would be willing to make permanent epoxy type bond if it would seal.

Thanks, Safari64

[joatmon]

Is there a problem with replacing the leaking fittings with with modern-day offerings? You mentioned that parts were re-surfaced, but if the mating end is still boogered up, a leak will result.

Sealing with epoxy is an option although it is treating a symptom rather than the problem.

A picture would help if you have access to a digital camera.

[Safari64]

Thanks, I would rather fix it right than band-aid/epoxy it but I figure replacement parts aren't available and I may have to "weld" it tight.

I'll try to get photo of it. The biggest problem I see with retrofitting to modern connections is the valve body threads are metric. Tubing is metric with metric/standard adapter at supply end. The whole darn thing was made in France and I can't locate metric tubing fittings.
Even tried in France! And Canada.

I'm figuring the aluminum valve body the connection goes to must have hair line crack or such, the leak is always exact same spot, very faint.

May have been this way for 40 years. Can't smell it, only happened to check each connection with liquid LPG spray bubble test.

[dwightdi]

Locktite makes a blue gasket cement which sets up between thin spaces. That is what I would use if a reasonable coating of thick wheel bearing grease or Vaseline did not seal it. Pressure is low and no chemical contact to wash it out so any very high viscosity material will seal it.

[Safari64]

good idea. if that will withstand low pressure LPG I'll try it.

[lewster]

I know it's your unit, but putting ANYTHING on a propane connection is a big no-no in the RV industry. Is it possible to replace the tubing with soft copper and brass flair fittings? Keeping the originality is one thing, but a potential safety problem is an overriding factor, IMHO.

[Boondocker]

Wouldnt it be quicker to just use some dinamite or C4?.

[azflycaster]

Originally Posted by lewster

I know it's your unit, but putting ANYTHING on a propane connection is a big no-no in the RV industry. Is it possible to replace the tubing with soft copper and brass flair fittings? Keeping the originality is one thing, but a potential safety problem is an overriding factor, IMHO.

I agree. If you need to run a new copper line, run it from the last connection (under the trailer). Lets face it, a small propane leak could make you very dead.

[Safari64]

Oh I'd be glad to run new lines around, under and over the trailer to the heater if I could find metric copper tubing and fittings. Its the main connection to the female metric threads on the valve body on the heater that leaks. new lines are moot unless I can seal up this particular joint.

So, how do I convert from metric banjo fitting to anything else?
Or find new metric banjo fitting and sealing washers?
This isn't the only Airstream with a Therm'x heater.

Or perhaps I should bale on originality and just put in an Olympic heater?
I really am not trying to build a toaster bomb!

[Pick]

If it is made of copper, just solder the area that has the leak. I had a small pinhole leak in my bathroom faucet line. This cure worked for that. If it will hold 40 PSI of water pressure, it will certainly hold a few oz. of gas pressure.

[dwightdi]

This is an old European type connector. They used it also on all the old European carbuerators in the 60's. I had them on a set of Zeniths on my Porsche. The aluminum washer gaskets are prone to leak, if not perfectly flat and clean. The fuel pressure was higher that you have your propane pressure. I used a Loctite gasoline resistant gasket sealant on mine when the gaskets got too bad and started to leak. Give it a try and test as you did before. You have nothing to lose by trying and testing. If there is a leak try and buy a new set of gaskets. This design of connector is great, if everything is perfect, but is a problem unless you get it right and tight. I presume that is why you do not see this type of design around anymore.

[Safari64]

Thanks for the help.
Tubing and banjo are copper, valve body it connects to is aluminum.
I tried loading pictures, couldn't get them loaded.

I suppose what I need is new aluminum sealing washers. Good thought. I have similar banjo connections on my Volvo SU carbs and Norton Amals. Perhaps British bikes are a source of new spares.

I'm trying permatex blue sealant. Curing now. Then I'll leak check. If sealed and it's impervious to LPG that might hold. Even Permatex website doesn't say and can't find MSDS.

I prefer to fix it right and seal it with proper parts.
But this is Alaska, it's cold and furnace drains battery.
Headed to Antarctica next month, I'll check down in Argentina for parts.

Thanks for the thoughts
Safari64

[69 Silverback]

Safari64,

Sounds like you are describing the exact same connections as on most foreign auto fuel injection systems. We allways replaced the aluminum or copper (crush) washers every time the connection was touched. I would think any auto parts house should be able to fit you up .

You being in Alaska , I don't know how easy it is to find an auto parts supplier. The washers should be a standard stock item.

Best of luck,
Loren

[overlander63]

While at your favorite auto parts emporium, take one of the offending washers with you, and ask if they have any copper gaskets in that size. If not, they also make fiber washers that would probably do better at sealing the leak. I would also have to strongly advise against using sealers or other chemicals on the fittings. Propane does have other things in it that may not interact well with chemical sealants.

[Safari64]

Thank you for the input. I think replacing the crush washers might do it. They are metric but something has to be close. Good ideas, I'll try auto parts store next time I get anywhere near one (40+ miles). Or perhaps the mail order place I get British bike parts from.
Will fiber washers hold up to propane?

I agree, even though the sealant did seal and shows no sign of leakage, it's not a warm fuzzy feeling knowing it could explode any moment. I have no idea how it holds up to propane exposure. I want it fixed correctly.

Thank you
Safari64

Alaska:
The last foreign country still friendly to Americans

[overlander63]

Originally Posted by Safari64

Thank you for the input. I think replacing the crush washers might do it. They are metric but something has to be close. Good ideas, I'll try auto parts store next time I get anywhere near one (40+ miles). Or perhaps the mail order place I get British bike parts from.
Will fiber washers hold up to propane?

I agree, even though the sealant did seal and shows no sign of leakage, it's not a warm fuzzy feeling knowing it could explode any moment. I have no idea how it holds up to propane exposure. I want it fixed correctly.

Thank you
Safari64

Alaska:
The last foreign country still friendly to Americans

Metric oil pan washers are available in 12mm and 14mm sizes. I am not sure if the fiber washers would hold up, but I would be more confident in using them, than using sealers on the existing washers.