Garage > Mechanicals

Replacing spheres on a 6.9

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--- Quote from: raftel on 19 December 2020, 03:33 PM ---Thank you for your responses!  Apparently I am not alone in this. Thought I would provide an update.

The right front accumulator was also giving me the same trouble.  I ended up undoing the fitting that connected it into the bleeder, and once I got that little U shaped tube free, I got it threaded in to the accumulator just fine. So I returned to the left front accumulator.

I had broken a short brake line on the left rear caliper, and I used the new line that I had purchased to repair that to chase the threads in the accumulator.  Went in just fine.  Then I took a new rubber brake line that I had not yet installed and used it to chase the threads on the hard line.  Also no issue.  Then I used a razor blade to chase the thread on the hard line, and removed a small bit of mashed thread.  It still won't go on - it threads a bit, has resistance, then pops loose.

Looking at the shop manual, the line goes to a T fitting somewhere (I lost track as the line went under the radiator, I'd love for someone to tell me where the T is) - how hard would it be to just replace that section of line?  Since it is essentially 3/16" brake line, can I get away with using a cupro-nickel alloy line as a replacement, as they are easier to bend and flare? I'm not sure about using flexible stainless line, as I would still have to cut back the existing steel line and flare it properly for the repair to work.

As always, appreciate the help.  v/r,  Robert

--- End quote ---
I used the Cu/Ni tubing on my brakes without difficulty and seems to work fine.  The pressure specs for brake lines far exceeds the working pressure of the suspension system, so if I were in your shoes I'd just go ahead and use it.  In fact, I'll probably be using it myself in the future - gonna rebuild struts and do some other suspension work.  Good luck!  Cheers,

I have used Cu/Ni/Fe ("kunifer", as we call it in Europe) lines with great success to replace sections of the SLS pipework on one of my W124s. The W116 system is more complex, but works on the same principle. The lines are 6mm on both I think.

On the W124 I've mated the the original steel lines with kunifer patches using stainless steel compression fittings from Swagelok. The system runs at ~130bar, and the 6mm kunifer lines are rated for continues working pressure of 150bar. The Swagelok fittings are rated for continues working pressure of ~350bar. Haven't had an issue with it since.

Thank you all for your responses on the use of copper-nickel alloy lines.  I'm especially interested to hear that Swagelok fittings will work - I used them extensively in grad school, but never at these pressures, and I had thought that swaged fittings were a no-no for brake systems.  That said, Swagelok has a lot more strength than most swaged fittings.

I'd like to report a tentative success.  I ended up buying a M10-1.0 die, and I ran it along the threads to clean them up.  I also loosened the 13mm nuts holding the accumulator in place, as well as the 19mm line to the strut.  This gave me some room to wiggle, which I used to get things threaded.  It all came together.

I started the car up, and after a few minutes, the car raised up.  I put it in the high position, and looked at all the connections.  Everything seemed tight.  My plan is to walk away from the car for a few days and see if it stays up.

Just for reference, the exact fittings I've used on the W124 SLS pipework were SS-6M0-6 "Stainless Steel Swagelok Tube Fitting, Union, 6 mm Tube OD".
From what I was able to find, standard 6mm steel tube with 0.8mm wall is rated to ~290bar working pressure, so even in this case there's plenty of margin.

Finally had a chance to drive the car with the new spheres.  I would almost say its transformed, but I know I have more work to do on the steering and front end components.  That said, I now have a better sense of that the intent of this system was, and the car better combines the ability to float over surface imperfections while handling well.


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