Author Topic: Replacing spheres on a 6.9  (Read 1377 times)

raftel

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Replacing spheres on a 6.9
« on: 14 December 2020, 10:51 AM »
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?

daantjie

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Re: Replacing spheres on a 6.9
« Reply #1 on: 14 December 2020, 11:22 AM »
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.
Daniel
1977 450 SEL 6.9 - Astralsilber

john erbe

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Re: Replacing spheres on a 6.9
« Reply #2 on: 17 December 2020, 02:51 PM »
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.

raftel

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Re: Replacing spheres on a 6.9
« Reply #3 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

daantjie

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Re: Replacing spheres on a 6.9
« Reply #4 on: 19 December 2020, 11:59 PM »
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.
Daniel
1977 450 SEL 6.9 - Astralsilber

raueda1

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Re: Replacing spheres on a 6.9
« Reply #5 on: 21 December 2020, 04:51 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
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,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

ptashek

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Re: Replacing spheres on a 6.9
« Reply #6 on: 23 December 2020, 06:10 AM »
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.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

raftel

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Re: Replacing spheres on a 6.9
« Reply #7 on: 23 December 2020, 01:34 PM »
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.

ptashek

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Re: Replacing spheres on a 6.9
« Reply #8 on: 24 December 2020, 02:10 AM »
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.
« Last Edit: 24 December 2020, 02:29 AM by ptashek »
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)

raftel

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Re: Replacing spheres on a 6.9
« Reply #9 on: 27 December 2020, 04:44 PM »
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.

daantjie

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Re: Replacing spheres on a 6.9
« Reply #10 on: 27 December 2020, 09:01 PM »
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.

Indeed it's a game of inches.  Steering coupler, idler arm bushing, subframe and control arm will need a hard look in addition to ball joints and sway bar bushings.
Daniel
1977 450 SEL 6.9 - Astralsilber

BCK1963

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Re: Replacing spheres on a 6.9
« Reply #11 on: 02 June 2021, 06:16 AM »
Lucas,
are you sure you used 6 mm OD fittings?  The hydraulic lines on my car have the diameter of brake lines: 4.75 mm.
Bernd

1976 Merc 6.9  since 2013
1974 Caddy CdV   since 1992  (for sale)

Rolo

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Re: Replacing spheres on a 6.9
« Reply #12 on: 15 June 2021, 02:32 PM »
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?

I replaced mine after strut rebuilds on Martin's recommendation, but to be honest, the shop and I couldn't tell much of a difference  What has changed is the fluid.  After flushing the entire system and washing out the tank, the oil is now clear.  I only have one piece of OEM rubber on the system and it's the front return hose which I can't figure out how to remove without major work.

ptashek

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Re: Replacing spheres on a 6.9
« Reply #13 on: 16 June 2021, 12:17 AM »
Lucas,
are you sure you used 6 mm OD fittings?  The hydraulic lines on my car have the diameter of brake lines: 4.75 mm.

On the W124 estate they are 6mm, which is where I was using the swageloks :)
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE (history, resto)