First of all, this forum or me take no responsibility for any work you do on your own car. If you do not have the confidence to do this type of work or think it is beyond you, get a garage to do it. This is the braking system and is quite important. Everything below is for information only.
This concerns work I am carrying out on a year 2000 VW Bora. The brake pipes that run from the front to the rear needed replacing. The pipes themselves are in reasonable condition but the unions onto the hoses at the rear of the car were seized and would not undo without twisting the brake pipe. This weakened the pipes and even if I did consider re-connecting them up to new hoses, I would always have a nagging doubt about it. So I'm doing the best thing and replacing them complete.
Brake pipe type and size.
The size of the pipe is 4.75mm fitted to modern VW's. Always check though on older cars and vans.
When you try and buy some though you will almost always see 3/15th's imperial sized pipe. This is absolutely fine to use as 3/16th is 4.7625mm or as near as dammit the same and within the tolerance of the fittings. It is probably why 4.75mm was chosen as it is so close 3/16 where 3/16 had been used for years and years.
Brake pipe fitting and the 'Flare'
You will need to buy some new metric fittings to suit 3/16 or 4.75mm pipe, these are readily available. You will also need to use the correct flaring tool so as to produce the correct flared end on the pipe. Older imperial flares are called SAE mainly although there are others. What we are concerned with producing is a DIN or metric male flares. See pic below to see the differences.
Brake pipe type
The obvious choice of pipe for a DIY'er is copper. I've chosen to use a copper nickel alloy pipe as it is stronger and more resilient than copper. If you dig around online you will discover a lot of people don't like copper and in some countries it is banned for the use of brake pipes. I will let you do your own research and make up your own minds. I'm using copper nickel though this time. I have used copper myself in the past with no problems.
Doing the doo...
This is the kit I'm using;
10mm and 16mm ratchet spanners for the flaring tool, pipe cutter, flaring tool and flaring tool grease, a flat file for removing any burrs. Bag of new unions and ignore the old brake hose.
Cutting the pipe, do this slowly turning the tension by small amounts only on the cutter so as not to crush the pipe. Then clean the cut end up, de-burr it internally using the tool on the cutter and lightly file any burrs off externally.
Now the flaring tool. I've used this old kit before which works fine on copper pipes but after a few test flares on the copper nickel it wasn't up to the job. You also need to use it clamped in a bench vice.
The flaring tool I am NOT using below, I am using the cutter from it though.
The new tool I've just purchased is called a "Powerhand" and having researched it, it seems to be the best one available for a reasonable price. Best still you can easily use it on the car. It is also "Made in England" !!! There are videos online on how to use it.
"Powerhand 4.75mm DIN" dismantled
Where the tube sits
DON'T FORGET TO PUT THE FITTING ON THE LINE NOW BEFORE IT IS TOO LATE !
Roughly insert cut and prepared pipe, finger tighten the 10mm bolts on the tool
Screw the die in, the flat end. This sets the pipe to the correct depth in the tool.
Tighten up the 10mm bolts
Undo the die, turn it round so the forming end is going into the tool, dip the forming end in the special grease first. Them wind it down tight with the 16mm spanner. This operation forms the flare.
Undo everthing and remove pipe and behold, there is the flared end.
Job done, below are a couple of practice flares.
For reference, you can see where the flared end bears upon the female fitting, in this case it is the old brake hose
