stop these compression fitting leaking

[Chotu]

Originally Posted by deblen

You need a flaring tool set.
Cut off your leaking flare & re-do it per this video.
Pay particular attention to inspecting the fit of the flared tubing against the flare sealing surface per video.Look carefully for cracks in the flare,especially in old copper tubing,which tends to get brittle with age.

Practice on a scrap piece of tubing until you get it right.
No sealant or teflon tape should ever be used on a flare fitting. If it leaks,just tighten it another 1/8th turn or re-do the flare.
Never use compression (olive in UK) fittings on anything that may vibrate or move during use & never on propane,nat.gas or gasoline-(flammables).
Cheers/Len

Uh... It’s perfectly fine to use on propane.

Works like a charm and doesn’t leak.

[Jammer]

Originally Posted by hd002e

I have these compression fittings in my diesel fuel lines and they leak, it is not kuch but it is enough to make everything greasy and stinky. How do i compat the mess? Any tricks? Thank you!

Yes, those are flare fittings. I've made many flare fittings and repaired many that I did not make. There are a few key points that posters upthread have missed:
You should inspect the flared end of the pipe. You're looking for cracks anywhere, and for folds on the sealing face. If either are present then you have to cut the pipe and re-flare it.

• Sealant shouldn't be used with flare fittings. Sometimes you'll get lucky and it will help but generally it leads to more leaks and makes the fittings a mess to work with in the future. But the mating surface, the threads, and the back of the flare that contacts the nut should all be lightly lubricated with oil before assembly. I use a drop or two of motor oil. Doing so allows sufficient pressure for the metal-to-metal faces to seal.
• The flare nuts should be tightened down quite snug, with considerably more torque than is used for compression nuts.
• As pointed out upthread, copper is usually not recommended for diesel lines because it causes diesel to deteriorate, posing problems particularly when the engine has not been run for several months. Steel lines are inexpensive and readily available and are the preferred material.

[deblen]

Originally Posted by Chotu

Uh... It’s perfectly fine to use on propane.

Works like a charm and doesn’t leak.

https://www.plumbingsupply.com/plumb...ng-connections


Flare for higher pressure,multi disconnect,better leakproofing.


Compression (ferrule,olive,etc.) for low pressure(domestic water,air,etc) where a minor leak is not dangerous. Not allowed for gas in ABYC or North America.
Allowed for gas in EU.


https://www.plumbingsupply.com/plumb...ng-connections

[Bycrick]

Pre-made propane hoses come with flare fittings.

Compression (ferrule,olive,etc.) fittings. Once upon a time, I had these on the burners for a pressurized kerosene stove. Once loosened, they never stopped leaking when retightened. I ended up replacing all the tubing with flare fittings. Problem solved.

[Uncle Bob]

Originally Posted by Uncle Bob

They are not a compression fitting but a flare fitting, the section that screws into whatever needs to be sealed, usually with teflon tape and then the flare nut is screwed down tightly onto it. I have them on my fuel system and they are great.

Perhaps I was a little unclear re teflon tape, the only part that needs some sealant is the male thread which fits into whatever it is fitted to, not the flare or nut, which as others have said, must not be contaminated with anything, strictly metal to metal.

[Bent Bugle]

The guy on that video has got it pretty right, I've done hundreds of flared joints, gas, water & diesel, I'll add to make sure you hold back on the threaded fitting as you tighten the nut on the flare, sometimes the nut will spring back & you need to loosen off & do it again, if you practice you'll get a feel for it...

[Russ]

Agreed new flare made with flare tools, No tape but you are supposed use a Flare nut Wrench. Like an open end but NOT the same. Regular open end wrench will crush the flare. I have all copper on my Diesel engine with No problems in 20 years I do use a black diesel sealant on the threads only to prevent loosening in the engine room.
Yellow Teflon was a disaster never again

[j.g.evans]

Copper compression fittings on a diesel engine, and I think this is true for CU flare fittings, harden under compression. I never reuse the flat compression washer on my engine. Air conditioning supply houses sell cupped CU washers that can be used in the flare joint. This way you have soft CU between the tubing and the brass fitting. Try this if you don't have enough tubing to cut it off and have a fresh, soft CU, flare.

[motion30]

Originally Posted by Emmalina

nothing wrong with them but you shouldn't use copper pipe for diesel !

Why shouldn't you use copper pipe for diesel fuel?

[Squanderbucks]

Best to cut it off and make new flare. Try a little oil on tubing we’re the flare tool expands and produces the flare. Sometimes soft copper will Gaul with dry not do smooth old tool.
If can’t redo the flare try FlareSeal Leak Free from Amazon. It is a thin soft coated copper flared piece of copper. Snaps over the Male part when the joint is put back together. I’ve used them in a pinch with success. Need to purchase the correct size to match your flare.

[deblen]

Originally Posted by motion30

Why shouldn't you use copper pipe for diesel fuel?

https://www.practical-sailor.com/boa...ng-up-our-fuel

[vpbarkley]

There are these but I don't recommend them: https://www.flaretite.com/flaretite-seal

Are you sure the nuts aren't loosening under engine vibration? A dot of blue Loctite on the threads could prevent that eventuality.

[garyfdl]

Originally Posted by Uncle Bob

Perhaps I was a little unclear re teflon tape, the only part that needs some sealant is the male thread which fits into whatever it is fitted to, not the flare or nut, which as others have said, must not be contaminated with anything, strictly metal to metal.

You shouldn't need to seal the threads. If the fitting leaks without the tape, it's not flared/seated properly and you're just using a band-aid instead of fixing it correctly.

To the OP:

DIY flared copper is done on soft copper tubing. Soft copper work hardens with repeated use - so every time you make up the joint and compress the copper female flare against the bronze male it gets harder - over time, that makes it difficult to get a proper seal.

There is an easy fix. Unlike steel, which gets harder when heated up and quenched, copper will get softer. SAFELY heat up the copper flare until it gets red and quench it in some water. Then take some sandpaper (120 grit is good)or a really, really, really fine wire brush on a drill or Dremmel and clean off any scale. Wipe the fitting clean and reinstall.

[Niall leslie]

Flared copper fittings work very well and are required for gas joints.
No sealant should be used with the flare nut fitting itself.
If you are going to undertake doing your own work with reliability be prepared to spend quite a bit of money on good tools and a lot of time learning how to undertake the job to a high standard. Normally that is what apprenticeships are for.
Good luck.

[Uncle Bob]

Originally Posted by garyfdl

You shouldn't need to seal the threads. If the fitting leaks without the tape, it's not flared/seated properly and you're just using a band-aid instead of fixing it correctly.

To the OP:

DIY flared copper is done on soft copper tubing. Soft copper work hardens with repeated use - so every time you make up the joint and compress the copper female flare against the bronze male it gets harder - over time, that makes it difficult to get a proper seal.

There is an easy fix. Unlike steel, which gets harder when heated up and quenched, copper will get softer. SAFELY heat up the copper flare until it gets red and quench it in some water. Then take some sandpaper (120 grit is good)or a really, really, really fine wire brush on a drill or Dremmel and clean off any scale. Wipe the fitting clean and reinstall.

Ahh, I get it now, you are advising that no thread should ever require any sealing product regardless.
BTW the advice to seal the threads was NOT the flare portion of the fitting so your advice may not be appropriate.

If perchance you glance at the original photo you will see a fitting with TWO threaded ends, one is the thread for the flare nut, the other appears to be a standard gas thread, this is the thread that would require some sealant, IMHO.