Reader Question: Splicing Brake Lines?

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Here’s the latest reader question, along with my reply! 

Rob asks: I’ve read it’s not safe to section together two piece of brake line that have been cut (as to remove a damaged section). What are your thoughts on this?

My reply: I think the risk of that joined section not being able to hold the line pressure is not worth whatever you save by not buying a replacement line. I’m about as far from being a saaaaaaaaaaaaafety freak as anyone I know – but this is something I would not gerry-rig. Note that factory brake systems never have such splices – unless they are at a threaded block fitting with the flared ends of the lines being secured by a nut, etc.

PS: You can save some money by bending/flaring your own replacement lines. It’s not difficult but it does require patience.

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  1. The splicing brake lines being ‘bad’ thing comes from the people who think that an extra fitting in the line somehow poses a danger. It doesn’t. I’ve never ever ever seen a brake line fitting fail. It’s always the line or hose. Some cars even have union fittings in a brake line from the factory, probably due to assembly steps and subassemblies.

    Anyway I’ve cut out bad sections of line and replaced them by adding a fitting, flaring the line on the car and using a union to connect to the new line segment many times without issue. That’s how it’s done properly. Using the proper flares and fittings. Eastwood has an on car flaring tool that makes this process much easier. Regular flaring tools are too large and often make flaring the end of the line that is still on the car a bigger pain than it needs to be.

    The wrong way to do it is compression fittings. Compression fittings are not rated for brake line pressures. However they have lots of margin for typical port fuel injection and carburetor fuel line pressures.

    The one thing to do is make sure to remove the entire rotted section. What can happen is that the remaining old line can still be rusted and fail at later date. Of course this doesn’t make a proper splice unsafe, it just means replace everything that’s bad in one go to save yourself time and effort.

    • Yep, Brent!

      A properly done (Flared ends into a threaded union) will be stronger than, and out-last the rest of the brake line. The taboo about sectioning brake lines comes from the ones that have been done with Scotty Kilmer style compression fittings (Which is illegal in most states, and if one lives in an inspection state, will cause the vehicle to fail inspection if caught).

      Hehe….years ago, I fabricated a section of brake line on a tow truck that I was selling- The piece with the coiled section in it that runs from the master cylinder to the proportioning valve. I lauagh because it wasn’t pretty (The coils came out pretty lop-sided, despite several attempts, using various items as a ‘mold’ to try and make tidy symmetrical coils)- but it worked just fine.


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