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6.9 suspension repairs - progress on trusty rusty

Started by s class, 21 October 2007, 07:26 AM

s class

Indeed, very sensible John.  The only reason I am going to these lengths on the suspension is that all the old lines were corroded and spewing out dirt and cotaminants. I was not willing to connect them to new struts and spheres. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

bronzy935

Hello Ryan, It was good to meet you in South Africa earlier this month and I thank you for your advice.
I managed to get rebuilt height adjusters from Star Motors in Endicott, New York USA. starmotors@stny.rr.com or call 1 607 786 3918 and talk with Conrad. Cost USD 650 plus USD 70 core exchange. Warranted for 12 months or 12,000 miles

I guess all you experts know this company but in case not their website www.starmotorsny.com has lots of useful info.
Kind regards
Neville
 

s class

#77
Right, a final set of photos to close off this thread now. 

I have discovered that in the 70's and since, Mercedes did NOT use cadmium plating, they used yellow and silver zinc plating.  Cad plating is no longer permissible in the auto trade due to environmental concerns.  Cad plating services are still available because its still permissible in the aviation industry.  I immediatley cancelled plans to have stuff cad plated after I heard this and I have switched to zinc.  Those little mounting brackets are now being redone in zinc. 

Anyway, in the interests of showing 'how its done', I thought I'd post these :

Every line was blown out with compressed air first.  Every line was blanked off at both ends before installing into the car to prevent dirt ingress.  As I assembled the system, all disconnected fittings were blanked off untill just before connecting.  Here's some ideas on how to do this :





Here's a practical example.  In this photo all the main steel lines have been installed and interconnected.  There is a blank inserted where the line to the right front sphere will connect.  The right front sphere has just been installed, also with its fititngs blanked.  The next step is to remove the blanks and install the little 'u' shaped line linking the sphere to the 'F' line from the levelling valve. 



[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

s class

The distribution valve from trusty rusty was no longer useable due to prior butchering.  I borrowed the one from the red car but serviced it before installing :

This device has three needle valves, each with a ball above and below it.  If you want to disassemble such a unit for cleaning, be VERY careful as the balls are not all the same size.  I would recommend disassembly in an orderly fashion, noting each ball and needle and where it belongs.  Also note that if you loose one of these balls you are stuffed as its not a standard size and not easy to replace. 

This is the bottom view of the unit.  The needles (removed before this photo was taken) run in the three bores you see.  Inside the bores are minute seals around the needle bores that cannot be removed, so do not soak this unit in solvent to clean it as you will ruin it. 




The next photo again shows the underside of the unit.  The three lower balls have been reinstalled in their correct location, and I've started closing off the apertures with the short bolts and new copper washers. 



The next step is to turn the unit over and from the top insert the three needles in their correct bores, the right way up.  The needles are very flimsy and easily bent so be careful. 

Then insert the three top balls in their correct locations :

In this photo you can also see the new top PTFE seal ring.  This is not available from Mercedes and its not a standard size.  I had some custom made by a specialist hydraulics seal company. 



I reinstalled the top disc unit, and finished off with a new rubber o-ring on the side of the unit.  This is the O-ring that seals the unit up against the pressure regulator.  This seal is available from Mercedes and its cheap. 



[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

s class

I also serviced the pressure regulator, with a complete stripdown which in hindsight was not necessary and probably not recommended anyway. 

I will show this photo :

The screw unit you see removed mounts into the face of the regulator that points to the rear of the car, right next to the steel line that sends regualted pressure to the 5th sphere.  The screw unit has a rubber o ring which I replaced (available cheaply at Mercedes), and it retains the little metallic gold coloured filter you see.  The filters are around $20 new, alternatively I soaked my little filter in petrol overnight.  I then blew it out thoroughly and made sure all the solvent had evaporated before reinstalling it.  The filter tends to pack up with rubber debris from the deterioration of the strut flex lines.  Blockages in this filter will result in the system taking longer (or even failing) to achieve proper pressure. 



[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

nathan

ryan, i know that after new spheres alone, my silver 6.9 drove like a million dollars - no exageration, it really was the nicest ride i recall...your car must now ride at least like a million and five dollars! :D
1979 116 6.9 #6436
2018 213 e63
2011 212 e63
2011 463 g55
2007 211 e500 wagen
1995 124 e320 cabriolet
1983 460 300gd
1981 123 280te

s class

Nathan, I'll say this.  My red car is a pretty well looked after example with 195 000km.  Struts and valves appear original.  I fitted new Febi spheres to it and I was impressed.  Now trusty rusty got a similar set of Febi spheres, plus the new struts and recon valves.  The difference between the cars is substantial now I'm sorry to tell you.  The red car feels loose and underdamped with its old struts. Trusty rusty feels super positive and sure footed, very precise, yet at the same time supple - you know magic carpet and all that. 

The down side to all this is that I'm lusting after new front struts for the red car as well now  :o


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

nathan

even though my beloved old silver mohican is over 300,000km (not sure if new struts, would have to check records), the new spheres made it an awesome drive.   i cant imagine how bluey goes with all that new stuff you put on!
please dont buy all the struts left at benz, the rest of us will want some when we win lotto!!
regards
1979 116 6.9 #6436
2018 213 e63
2011 212 e63
2011 463 g55
2007 211 e500 wagen
1995 124 e320 cabriolet
1983 460 300gd
1981 123 280te

koan


s class, that's excellent info on the distribution valve and regulator. I would be interested to know what the valve feels like when installed. Mine is quite free when there is no pressure but very stiff to move when at operating pressure.

Just been looking through the gallery pictures and saw the colour of your fluid (suspension) you talked about earlier.

About 12 months ago I replaced front struts and cleaned out the tank. I flushed out the old fluid by operating the height control levers with fresh fluid in the tank and collecting the return fluid at the fitting on top of the regulator that normally returns it to the tank.

Now, in the middle of replacing spheres the fluid is again dark, though probably not as bad as yours was. I can only put it down to foam rubber in the spheres decaying.

I'm considering reusing the fluid after filtering as I think it is just dicoloured rather than contaminated.

Any thoughts on that?

koan
Boogity, Boogity, Boogity, Amen!

s class

Hi Koan,

My distribution valve is smooth and easy to operate when there is no pressure.  When the system is in normal operating condition, the valve is smooth yet quite stiff to rotate.  It engages the various detents very positively. 

koan there are two reasons it seems for the fluid going dark - sphere degradation and degradation of the rubber strut hoses. 

I replaced the strut hoses but they are quite expensive - around AUS$85 each. 

If you want to reuse the fluid, just make super sure there are no particulates in it.  I wouldn't do it myself, but then again I pay around AUS$12 per litre for the fluid, which as I understand is somewhat cheaper than what you guys pay. 

The other possibility is that perhaps your flush of the system 12 months ago was not as thorough as you thought - the struts hold a lot of fluid.  When I changed spheres on the red car I flushed the system,and this included compressing each strut to eject the old fluid from it.  Basically, the car was on stands, and at each wheel I disconnected the sphere, then raised the relevant wheel hub to compress the strut, then lowered it again (drawing in air), and connected the new sphere. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

WGB

Wonderful information Ryan and the photos make for excellent clarity.

I think you are very brave but thank you for being a trailblazer.

I too will be in the market for new front struts some time as my 6.9 has a similar feel to my 126 before I replaced the front shocks- please leave us some left in the world. ;D

I notice that the article from Star Motors NY http://www.starmotorsny.com/pdf/HydroSuspGuide.pdf treats the system and particularly the struts as a disposable whole to be replaced at 10 year 100,000 miles intervals.

They also state the struts are rebuildable and certainly this will likely become necessary in the future.

What I find less commonly discussed is the effect of deterioration in the bushes and strut ball joints which I would believe occurs long before the hydraulics start to fail.

Bill

s class

Thanks Bill, I'm familiar with that star motors guide.  What I do find surpsising is the rather offhand statement that the strusts are rebuildable.  I guess they could well be, but generally this seems not to be easily done.  I know GrantV, after replacing his front struts, sacrificed one of the old ones in the name of research, but came up against dead ends at hydraulics places.  Styria has managed to open struts and install new seals I believe, but he is cautious about them as they are not yet tested. 

I accept that the seals in the struts probably can be successfully replaced, but I understand there are also some baffle plates in there that control the fluid flow rate.  If the orifices in the places have been enlarged of the the years by erosion, they will feel underdamped.  Perhaps someone like styria or GrantV who have seen inside these things can comment.  The other concern is that the struts are very tightly assembled, and considerable brute force seems necessary to open them, carrying with it the danger of distorting the tubes out of round.  Trusty rusty's old front struts appear to have suffered from this at a prior overhaul attempt. 

And you dont need to worry about me buying more struts any time soon for the other car - financial constraints will prevent that for some time to come. 

Agreed, the upper and lower strut mounts are important and liable to deterioration - its just a little disappointing that they are so expensive. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

koan


"s class", the description you give of your valve sounds much the same as mine.

Not sure about reusing the fluid either... I have to remove a front hose to fix a seepage, I'll give it an internal probe and if it appears to be decaying I'll get new hoses made up using the old fittings and start again with clean fluid.

Your flushing method probably expelled more old fluid than my approach.

koan
Boogity, Boogity, Boogity, Amen!