Fuel leak at firewall

[FlyingMonkey]

Interestingly, I found the following in the FAQs when pricing out teflon hoses...sounds like it buys you 3 years, not a lifetime:

My mechanic told me that Teflon hoses are lifetime, is that true?

No, regardless of hose type, it is recommended to replace the hose after 8 years or at overhaul of the engine.

[John Vance]

Teflon hoses have their issues as well, and don’t have infinite life.  This Australian Airworthiness Bulletin explains some of the tradeoffs (see paragraph 3.5).  I started down the path of obtaining an MRA forTeflon hoses last year,  but ultimately decided against it , at least until I know more.

 

awb_02-006_issue_2_-_flexible_hose_assemblies_-_maintenance_practices.pdf

[Madhatter]

Just remember the lawyers are involved. Most certified teflon with integrated firesleeve hoses are considered good till engine tbo. When you use these hoses inside a cabin I think they will outlast us. They also will survive intact in an accident. They are infinitely better than automotive hoses and do not depend on barbed fittings and clamps. I have never seen barbed fuel line fittings on any aircraft ever.

[FlyingMonkey]

How would you get teflon hose on the fittings out of the A pillars and similar locations?  Would you hack off the barbs and tap the stubs for new fittings?  How would you handle the coolant hoses?  Just trying to get my head around how all this would work and the expense.  It sounds like a $3k or more project without labor.

[Madhatter]

Only fuel and oil lines, the barbed fittings can be changed to AN fittings same with oil line fittings.  I've done some already.  You could even use areoquip AE 701 hose and the fittings are reusable. A "hose to AN fitting" can be used where the aluminum fuel line exits the cabin. I have been looking at this for over a year and I don't see any issues (so far). I'm wrapped up in a CT exhaust project right now, it keeps me out of the street .

[Anticept]

2 hours ago, FlyingMonkey said:

How does that work with things like barb fittings?  Do you need new connection methods, or some kind of end cap on the hose to prevent damage before going over the barb?

The teflon is easily cut. Barbs and worm drive clamps will actually shred it. That's why the fittings on the hoses to the carbs are the way they are. Crimp on connectors are a good bet, but there might be other solutions out there, the hose manufacturers will have recommendations.

Teflon hoses do have a very, very long life, but I should mention: they become hard over time. They're still functional even when hard, but they also become brittle and will break if you bend them too much after that.

[Madhatter]

Never seen it. I make up AE 701steel braided teflon hoses with Eaton fittings that are designed for it and I pressurize them to 1000psi. Never ever seen a failure on teflon hoses. I have teflon silicone firesleeved hoses on my carbs with AN fittings. I've been dealing with these hoses for a long time and there is nothing better.

[Anticept]

5 hours ago, Madhatter said:

Never seen it. I make up AE 701steel braided teflon hoses with Eaton fittings that are designed for it and I pressurize them to 1000psi. Never ever seen a failure on teflon hoses. I have teflon silicone firesleeved hoses on my carbs with AN fittings. I've been dealing with these hoses for a long time and there is nothing better.

Wholly agree, but I have myself run into very old teflon. Still strong, but stiff.

Barbed fittings + clamps is what I mean when I say avoid. Barbed fittings aren't supposed to be used with clamps, that's what beaded fittings are meant to be used with.

When you say AN fitting, are you referring to the compression type that uses an internal tool to lock the insert during the first part of installation? Or some variation of that? Those are fantastic, but yowza they are expensive!