Installing braided brake lines & master cylinder

[Casey]

The brakes on my car have never felt confidence inspiring. They work, but the feel is softish and there is a tendency for the pedal to move further down when held for a while, on coming to a long halt. I have checked the fluid and bled the brakes, but with no improvement. The brakes have passed 2 MOT’s, but I suspect the brake lines and/or the master cylinder to be the cause of the poor feel. There are no leaks and the car will brake in a straight line, locking the wheels evenly if enough pressure is applied. The servo appears to be holding a vacuum for over 2 weeks and the vacuum pipes are OK.

So, in the knowledge the flexi-hoses and the master cylinder are nearly 40 years old, I have decided to bite the bullet and replace all 5 brake hoses and the master cylinder.

This topic will cover the replacement of the hoses with braided lines. I’ll start a separate topic for the replacement of the master cylinder.
For those who have done this job many times and can make brake flares blindfolded, you can skip most/all of this topic, intended for those who, like me, don’t do this task very often. I thought a detailed write up might assist others who fancy taking on this very satisfying task.

I have bought the braided lines from HEL: https://auto.helperformance.com/hel-bra ... -1979-1985, price £125. I went for the black carbon fibre option, to keep an OEM look.

Why they only list one product, for the turbo version too (and covering the entire S1-2-3 manufacturing period), is a slight disconcerting. In my experience, Mazda just love to make subtle changes to parts between the different series, so I’ll find out shortly if there is any problem with fitting these. Initial visual checks of hose lengths and fittings is promising, although the front hoses do look to be about 5-10 cm longer than OEM on my S3. No problem, as long as that extra length doesn’t cause the hose to catch/rub anywhere.

I have started the task and, as predicted, rusty fixings are making the task more challenging!

I'll update this topic as and when I make progress over the next week.

[Casey]

First task was to crack the wheelnuts all round and get the car up safely on stands, then all the wheels off.

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[ian65]

do they give the same part number for all 3 series ... (S1-S3)? I think S1 and S2 brake hoses have a different thread pitch to the S3 hoses don't they?
Looking forward to following your progress Malcolm, there's something strangely satisfying about flaring your own brake lines

[Casey]

To stop the fluid leaking out too rapidly when removing the hoses, I placed some plastic under the master cylinder cap to create a vacuum.

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I went around cleaning around all the hose fixing areas to help prevent dirt from getting into the system later, then squirted penetrating oil on all the fixings and left this to soak in overnight.

The next day I applied another dose of penetrating fluid to all the fixings and then started on the front passenger side by removing the spring clip holding the centre hose support to the bracket on the suspension strut. The hose can then be freed by jiggling the hose support forward, then down through the notch in the bracket.

(Driver's side shown)

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The next step was to crack the flare nut on the bulkhead bracket and the hose into the caliper. Using a good quality flare spanner was essential, as the years of exposure to road grime had created quite a bond between the hose and the flare nut and they were reluctant to part. Once both had been cracked, I unscrewed the flare nut completely, capping the end with a bleed nipple cover, which successfully stopped it dripping. The spring clip can then be removed (tapping with a screwdriver and hammer needed!), and the hose fixing pulled out:

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The hose can then be unscrewed from the caliper end and removed.

[Casey]

I think S1 and S2 brake hoses have a different thread pitch to the S3 hoses don't they?

It would seem not. I tried the HEL lines into some spare S2 calipers and they fitted fine, as they do with the S3 calipers.

[Casey]

The HEL hoses look to be well made and are a close match in length the OEM hoses. The only perceptible difference is that the front hose are about 3-4cm longer, which shouldn't present an issue. I will carefully check for any possible rubbing or snagging after fitting. Here are 3 of the 5 hoses; front, rear and axle mount. Fresh copper washers are provided.

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The centre support on the HEL line is not fixed, but can slide along the hose. There are some plastic clips provided to attach both sides of the hose. When in position, these restrict movement. Instructions for positioning/fixing these "stops" this are provided with the hoses.

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[Casey]

One snag arose in fitting the front hose into the bulkhead mounted bracket - the HEL fitting was about 0.5mm larger than the hole in the bracket. This required the use of a Dremel grinder to take off a very small amount of metal. After that, the new hose was bolted with the new washer onto the caliper, the centre fixing fitted to the strut mounted bracket and the other end fitted with the spring clip into the slightly enlarged hole on the bulkhead bracket. The existing flare nut screwed easily into the new fitting, just requiring a bit of a careful clean up of the few ml of fluid that inevitably was lost in the process.

The last step was to fit the spring clip into the centre mount and check the hose position by turning the steering wheel to both extremes before affixing the two plastic "stops". I'll need to re-check for clearance when the suspension is compressed later.

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No further issues were discovered in fitting the front driver side hose, just the same need for a bit of Dremelling.

[Casey]

Removing the rear brake hoses was pretty much the same process as for the front EXCEPT the position of the hard line flare nut is such it has had full exposure to the elements for nearly 40 years, so the hard line had "fused" onto the flare nut. So, although the nut (surprisingly) was relatively easy to free from the thread in the hose, the hard line twisted with it

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This was the same for both sides. Also, the 5th hose would not come free from the T splitter on the axle - the other end is in a shielded position and looked like new and easy to remove. I therefore decided the best option was to cut the two rear hard brake lines and re-make them.

The new rear hose went on easily.

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[Casey]

Freeing the 3 fixings into the very rusty "T" splitter mounted on the axle was not easy. I was about to resort to heat but tried one final time with the T firmly in a vice and a 6 point 17mm long spanner on the hose nut when gentle persuasion of a lump hammer finally freed the connection. Penetrant had been soaking in there for days with little effect it would seem.

Just for reference (handy when you find yourself on the floor with the wrong tool to hand ) the caliper end fixing nut on the OEM hoses is 17mm and the HEL ones are 14mm!

The other two flare nuts in the T were also reluctant to free their grasp, so I cut the pipes close to the nuts so I could put on a 6 point 10mm socket. They surrendered fairly easily when faced with this attack

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Defeated!

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T splitter de-rusted and sprayed before re-installing, together with replacement s/steel 6mm bolt.

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[gt_james]

Nice write up Casey. Just thought I'd add to this some thoughts having done brake lines recently. You might well know all this yourself, but anyone else reading this in future might want to know.

I believe either series 1 or series 2 is a different thread pitch for the brake unions, so unlikely these HEL ones fit all models, but I've only ever fitted HEL and goodridge hoses to a Series 3 brake set up.

Agree on using a proper brake pipe spanner, definitely worth buying one. Expect though when fitting braided lines on an old car, you're likely to find the unions rusted up, and undoing them will often damage the hardline which will need remaking.

For brake hardlines do not use regular copper pipe, it work hardens and becomes brittle, and can often shear off at the union, leaking all the fluid out and leaving you with no brakes. In many countries it's illegal to use copper for this reason. The stuff you want to use is copper nickel, also called cupro nickel or kunifer. It's still soft enough to bend by hand and easy to flare, doesn't really cost much more, and miles safer. You don't need a bending tool, you can bend kunifer brake lines by hand, go stead and if you kink the pipe, start again. The size for the RX7s is 3/16th.

Unions and flaring, firstly buy the right unions and flare tool for the type of flare your car uses. There are differences and I found this out the hard way recently doing the brake pipes on my race car. The 84-85 S3 RX7s at least use the SAE double inverted flare, so get a flare tool that does this type of flare. The unions you need to buy are M10x1 thread, fully threaded to the end, and with the correct seat for the inverted flare, with a 45degree inside cone. Must fit the 3/16" pipe. The mushroom flare type unions with no inside cone or an outside tapered end won't work. Ask me how I know! Then remember to put the two unions on the pipe before you get carried away flaring and bending.

A quick note on the HEL braided lines, they are supposedly compatible with the inverted flare and the mushroom flare. Bit of an oddity but work fine, I've never had an issue. Like you mentioned, they use a different size spanner to the stock ones on the ends, and goodrich use different again. Minor inconvenience for me as I have goodrich on the rear axle and HEL everywhere else. Also a minor inconvenience whilst changing from stock to braided.



For the master cylinder, before you put the new one on the car, make up a copper brake pipe (a good time to practice flaring and bending!) that goes from the outlets straight back into the reservoir and bench bleed the master, will save a lot of time doing it dry on the car.

Series 2 and 3 use different size masters. Can't remember what sizes off the top of my head but I can get the sizes if needed.