Found a weird trick for stuck AN fittings on a Cessna 172's fuel line

I was working on a 1978 Cessna 172's fuel selector valve in our hangar last week, and the lower AN fitting was seized solid. Instead of cranking on it with a wrench and risking damage, I tried something my old instructor mentioned once: a 50/50 mix of automatic transmission fluid and acetone. Brushed it on, let it sit for about 20 minutes, and it broke free with way less effort. Anyone else have a go-to penetrant for old, corroded fittings on general aviation birds?

3 comments

3 Comments

casey_henderson24d ago

You used acetone on an airplane fuel line?

emma30324d ago

It's wild how many people will use a harsh chemical because it's handy, without checking if it's safe for the material. You see it all the time with cleaning products too, where something strong enough to eat through a finish gets used on a surface it'll ruin. It seems like a general habit of grabbing the quick fix without a second thought. That kind of shortcut can get really expensive, or worse, when you're dealing with something as critical as an aircraft part.

gray_roberts1h ago

What, you've never used nail polish remover for a little impromptu aircraft maintenance? Look, it was right there and the label said 'removes stuff'.