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Replacing spheres on a 6.9

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One of my early winter projects has been the replacement of the spheres on my 6.9.  The Classic Center hooked me up with new spheres in original Mercedes packaging.

I hadn't replaced the spheres in over 10 years, and it showed.  Car was riding like a harsh pogo stick.  I got the car in the air, and as the fluid flowed out of the old spheres, it was light brown and finely aerated, practically effervescent. Good thing is the fluid was fairly clean.  I got the central accumulator out, and it must have been at least 20 years old.  It was full of fluid.

I'm waiting to replace the lines to the struts until I secure some new crush washers, but I am having a problem getting a supply line hooked into the left front sphere.  It appears that the threads on the hard line may be a bit damaged, and it is not threading on to the new sphere. How may I go about cleaning up those threads, and failing that, can I use appropriately sized steel brake line as a replacement?

Indeed yes, I have had to resort to these measures too as that area is super prone to rust seeing as it is in the wheel well, so on an older swap out (spheres not changed for many years) you invariably end up with a wrench dance.  I have used the metric bubble flare lines with great success, you can usually find them in various lengths, the ones I got even had the nice olive green coating on it so it looks quite nice installed.  You do need good flare wrenches for this job and counterhold as much as you can.  Usually some localized heat with a propane torch goes a long way as well.

john erbe:
I had same problem back in the day, cross threading and difficult to line-up into accumulator when you're lying on floor with car up on blocks. My solution was to  replace that last stretch of rigid line with braided stainless high pressure hydraulic hose from a local shop and take it one step further by having them put a swivel at the end both giving ease of installation. Cost was relatively inexpensive.

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.


To my knowledge there is a t connection at the bleeder valve (if fitted) under the battery tray so you can tap in there.  The lines run along the bottom of the rad support where you will also see the cooling loop for the hydro fluid. There should be no t connection under the radiator from memory.


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