How to clean brake lines

[pflaming]

What is recommended for cleaning old brake lines before putting new brake fluid in? I may replace them, but my truck is a dry climate truck so I'm debating doing that. I know the arguments for new lines.

[Rusty O'Toole]

You could blow them out with compressed air.

In the old days they used to flush with alcohol but you have to get all of it out or it could cause brake fade.

Better to just blow out the lines, refill the system, and bleed out fluid until it runs clean.

If the lines are real bad, replace them.

[oldmopar]

I use a product all brake kleen I think its made by crc

[TodFitch]

if there's rust on the outside surface, eventually that rust will form a pinhole somewhere...new tubing is cheap insurance on these brake systems

Actually the problem is that traditional brake fluid is hygroscopic. That is it absorbs water from the air. Over the years, even in a dry climate, you get water inside the lines so they can rust from the inside out. Unfortunately you can't see the rust inside the tubing so you don't know you have a problem until the tubing is so rusted that it fails on brake application. Most likely on heavy brake application when you need it the most.

For safety factory brake lines on vehicles as old as we are dealing with should be replaced regardless of how good they look on the outside.

[JBNeal]

internal corrosion is implied if external corrosion is present. Steel tubing is subjected to harsh corrosive effects of humidity, salt spray, road chemical wash, etc. Brake fluid absorbs moisture over time, so the thin walls of the tubing are being attacked on two fronts. By the time the tubing outer surface begins to corrode, the internal surface has already begun to corrode. Much like stinky exhaust is indicative of a poorly performing engine that has sky-high carbon monoxide & NOx emissions (which are odorless), a rusty lookin' brake line is a corroded brake tube.