Author Topic: Rebuilding 6.9 struts  (Read 1491 times)

daantjie

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Re: Rebuilding 6.9 struts
« Reply #15 on: 26 February 2021, 05:08 PM »
Nice work Dave ;)
Daniel
1977 450 SEL 6.9 - Astralsilber

raueda1

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Re: Rebuilding 6.9 struts
« Reply #16 on: 26 February 2021, 05:17 PM »
Nice work Dave ;)
Thanks, but don't get too carried away quite yet.  Today I went 1 or 2 steps backwards.   >:(  The issues:

1.  Disassembly of first front strut went very smoothly.  I paid for that today.  Today's cup was in much worse shape, clogged with an enormous amount of dirt and very rusted.  Long story short, I had to cut it off, destroying completely.  :o  No loss, as it was terrible anyway.  Still, now I need another cup.  So, if anybody has a front strut cup just laying around I'd be very grateful for it.  I can probably get you a replacement when I get the struts off the car, though that wouldn't be for a couple months.  Anyway, please PM me if you can help.

2.  I just noticed that one of the rear struts has a weird part number.  One is 116 320 3613, as it should be.  The other is 116 320 2813.  They look identical.  Can anybody shed any light?

Thanks greatly for any help anybody can offer.  The adventure continues.......   Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

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Re: Rebuilding 6.9 struts
« Reply #17 on: 26 February 2021, 06:35 PM »
Dave, Martin/Thomas sell the new cups, I bought a set from them not too long ago,  top notch quality.
Daniel
1977 450 SEL 6.9 - Astralsilber

raueda1

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Re: Rebuilding 6.9 struts
« Reply #18 on: 26 February 2021, 07:16 PM »
Dave, Martin/Thomas sell the new cups, I bought a set from them not too long ago,  top notch quality.
Sweet!  I reached out to Thomas.  I'm saved!
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

tcj

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Re: Rebuilding 6.9 struts
« Reply #19 on: 26 February 2021, 11:28 PM »
regarding 2813 and 3613: 3613 replaces 2813, some internal changes/improvements. Both match your car.
112.021
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116.036

raueda1

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Re: Rebuilding 6.9 struts
« Reply #20 on: 27 September 2021, 08:10 AM »
Case closed, and with a very happy ending.  I thought it would be illuminating to share it.  I'm recently back from the long road trip that I feared - ~6500 miles from Utah to New England, NY etc and back again, about 5 weeks.  I may report on that elsewhere, this is about the struts.  Conclusion:  the rebuild resulted in a vast improvement!  Here are the details.

To hone or not to hone? As rumb noted, the topic seems to be controversial.  Following the advice of the hydraulic shop I used a small ball hone and managed to get a decent 45 deg crosshatching.  Cleanliness is everything, so after wiping clean I used an ultrasonic cleaner followed by progressive solvent rinses (water --> isopropanol --> carburetor cleaner).  The cylinders were VERY clean). 

Leaking:   I just had car on the lift for oil change and general inspection.  There's not the slightest trace of suspension fluid leaking, dripping or anything else.  That includes the hose fittings (all of which were rebuilt as described elsewhere).

Spheres:  The front and central spheres were replaced last summer with Febi units (if I remember right).  Rear units were replaced with MB units during this job.

Ride and handling:  This is really quite fascinating to me.  Before the rebuild the ride seemed great, though notably soft.  VERY soft in fact, truly the magic carpet ride, maybe too much so.  The car had a lot of body roll when cornering at moderate speed (e.g., highway ramps).  It could be disconcerting because the front had a tendency to dive and oversteer and rear somehow not quite coordinated.  Hard to describe.   But if somebody else was driving the car I'd warn them that hard cornering was a bit weird and not to do it.   The change after the rebuild was profound.  Ride became significantly firmer, still relatively soft but much more like what we'd think of as a "modern" feel.  Yet the isolation and softness over bumps, road expansion joints etc was still superb.  Amazingly cornering was greatly improved - less body roll, and cornering was just far better controlled somehow.  No more weird dive or transitioning to oversteer. 
      Could the spheres be contributing?  Well, the "wallowyness" was present when I got the car.  Changing the front and central spheres last summer didn't change it.  Would new rear spheres do something?  The old ones seemed to work fine, so I don't see how.  I can only conclude, maybe, that wear or maybe an earlier strut replacement on one of the axles caused the front and rear struts to have different properties somehow, and now they're all the same.

The bottom line:  I undertook this job mostly to get rid of the leaks and not worry about the struts again.  I never thought that struts could become tired over time.  I just figured that they'd work the same afterwards.  Well, apparently they DO become tired.  The new ones did NOT work the same, they worked a lot better.  If you have a nagging suspicion that your ride and handling aren't quite what they should be, I'd highy recommend this job, even if your suspension seems to be "working fine." 

Now off to rack up another 1500 miles on yet another road trip - Palm Springs California, Las Vegas (again!) Zion Nat'l Park.   What great cars these are!  Happy motoring and cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Eyeman

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Re: Rebuilding 6.9 struts
« Reply #21 on: 29 September 2021, 09:58 PM »
Glad your suspension work as successful.  I finally got my car back from an over year long suspension overhaul.  Seems back to how my car always handled.  The only problem is the car now sits around two inches higher than before.  Is there some way to set our cars to have a certain ride height and my mechanic just set things high?  Or do you think my car will "settle" somewhat in time?

daantjie

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Re: Rebuilding 6.9 struts
« Reply #22 on: 29 September 2021, 10:11 PM »
Check if the H setting has not been activated (dash knob all the way out).  With knob fully pushed in this is the N (normal driving) position with selector disk on the height control valve fully against the stop.  Your arms on the leveling valves need to be level in this position, between "L" and "F".
Daniel
1977 450 SEL 6.9 - Astralsilber

rumb

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Re: Rebuilding 6.9 struts
« Reply #23 on: 30 September 2021, 07:06 AM »
There are adjusters on the leveling units.  Somewhere buried in forum is how high a 6.9 is suppose to be.  The official MB method used location points on the chassis and tools that dont exist.  Some ppl have come up with an actual measurement of wheel well heights.  Maybe someone can find this info.

Here is the first I found:
https://forum.w116.org/mechanicals/6-9-ride-height-7295/msg77911/#msg77911
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

rumb

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Re: Rebuilding 6.9 struts
« Reply #24 on: 30 September 2021, 07:41 AM »
Here it is:
https://www.m-100.co/content.aspx?page_id=2155&club_id=406485&item_id=828332&message_id=2113650&fs=1&sp=ride%20height&#req

One measure is from center of roof: Overall vehicle height (constant) is given as 55.5 inches

fender well to ground seems to be:Front 26" and Rear 25"
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Eyeman

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Re: Rebuilding 6.9 struts
« Reply #25 on: 30 September 2021, 07:45 AM »
Thanks for the info that there are adjusters.  For sure my car is sitting too high.  This mechanic is weird, but it's getting hard to find anyone to even work on this type suspension anymore.