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How to make a brake pipe/use a flaring tool

Les Henson

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The following is how to replace a corroded brake pipe and make a duplicate - using a brake pipe flaring tool.

Brake pipes are usually quite fragile by the time they have to be replaced - the ends are quite often seized, and a spanner just rounds them off - requiring mole grips or other drastic measure to remove them. Bleed nipples snap off, and then the cylinder has to be replaced as well, so quite a bit of care is required to do this job.

The vehicle is an early 90, and has failed the MOT. Some MOT stations just list the failed item on a failure sheet, and some mark the fail with chalk/crayon (usually yellow), as in this picture.


This is the drivers side rear brake pipe - it runs from a T-piece that's bolted to a bracket on one of the diff housing bolts.

Runs across the back of the axle tube, where there's one pipe clamp, and then to the rear of the brake backplate to the wheel cylinder.


Special tools required are a flaring tool - they are not very expensive to buy, and although there are many different types - they all basically do the same thing. This is my portable one - it does just the two different ends for 3/16" copper or steel brake pipe - single flare (the end looks like a trumpet), and double flare (the end looks like the head of a mushroom). You must always make up the same end as the old pipe to avoid leaks/possible brake failure.


This tip makes the single flare (or trumpet)


Double flare (or mushroom)


A packet of brake pipe -25 feet of it usually.


Place a clamp on the flexi pipe to prevent the system from emptying when the pipe is removed. You can buy a proper pipe clamp that exerts just enough pressure to close the pipe without damaging it. Careful use of mole grips is just as good.


Pipe ends are usually 11mm, so an open ended spanner that's a good fit. It the spanner feels like it's going to slip, then stop and resort to a pair of mole grips. If that doesn't work either - cut the pipe where it enters the fitting and use a socket.

The single pipe support clamp normally shears off when you try to udno it. If this happens you will have to use cable ties to secure the new pipe.


The bracket on the diff casing that supports the T-peice is easily bent, so support it with a pair of mole grips while undoing the pipe end.


If you're lucky, the pipe will come off in one piece.


Carefully measure the length of the old pipe - add a small amount to be on the safe side.

Make sure you have the right pipe fittings (these are 10mm male). Copy the shape of the old pipe, taking care when making bends to not kink the pipe (I use a 12mm socket to do this). Put a new pipe end on before making the end up.


New pipe all finished and compared to the old one.


Place new pipe in position - make sure the pipe ends are lined up in their respective holes - the thread is fine and can easily be stripped. Don't over-tighten the ends either the copper pipe is soft and will seal with ease.


Bleed the system as normal (both sides at the rear) press and maintain heavy pressure on the brake pedal for about a minute, and then check for leaks - tighten any joint a small amount more if necessary and re-check.

Few things to remember:-

Make sure you make the same pipe end as the old pipe.

3/8" and 10mm pipe ends have a very similar thread, so make sure you have the correct ones - you can use the old ones at a pinch - providing they are not damaged.

Take care not to kink the brake pipe.

Make sure the new pipe doesn't rub or vibrate against any other part of the vehicle - it could cause a leak at a later date.

Les. :)

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Also bear in mind metric and imperial flares are different, and the cheapo flaring tool sold by Machine Mart is only recommended for soft copper and aluminum !!!! pipe, NOT cupro-nickel Also the tool is carp, it can produce lop-sided flares if you're not careful.

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Guest diesel_jim
Also bear in mind metric and imperial flares are different, and the cheapo flaring tool sold by Machine Mart is only recommended for soft copper and aluminum !!!! pipe, NOT cupro-nickel Also the tool is carp, it can produce lop-sided flares if you're not careful.

Yeah, and it doesn't grip the pipe very well, meaning the pipe slips through leaving huge great gouges in the pipe....

How do i know? :rolleyes: i bought one! :lol:

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  • 9 years later...

Be aware that copper rather the cunifer is susceptible to fatigue failure through either being loaded (particually when poorly supported) or through hydraulic pressure cycling and the hoop strains this induces. It is banned for use in many (most?) places other than here.

Stainless Steel and Steel are other options and while corroded pipes look bad there is a margin of safety in the wall size of the steel pipes that mean regular inspection should spot a corrosion issue before the pipe fails. A pending fatigue failure crack can be hidden internally right up to the point of instant and complete fail of that circuit.

Edit: Here = UK

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I think this is the standard listed on the label of the piping:


It had been superceded by a few years at the time of the photo and the standard (by that pages description, not buying it!) doesn't directly refer to braking systems or mention fatigue testing.

Edit: Also could have been bs 2871-3, which is also superceded and refers to piping for heat exchangers. Shouldn't give any confidence in its suitability for use in braking systems.

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Always worth having a look at the BS website to see what you are being quoted.

This site:


...quotes 2 standards. Both about production and testing of copper tubing, But niether current and the second actually supeceded the first standard! We're a good time from the 1930s when it was used in production cars. Are there any examples of using copper brake pipes (rather than copper-nickle-iron alloys) in current production cars?

Edit: Apologies, three posts on the trot look like I'm having a rant! :-D I should explain I'm away on work, bored, and reading up on brake lines as it's another job I need to do. It has been over 10 years since I did it on my beetle and remember throwing a flairing tool out in frustration and buying a pre cut set! I wasn't aware of the concerns about copper until coming across it in relation to some getting rejected at IVA testing and the bans in other countries.

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