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Garage => Mechanicals => Topic started by: adamb on 23 February 2020, 05:19 PM

Title: New 6.9 rear suspension spheres and other work
Post by: adamb on 23 February 2020, 05:19 PM
Today I replaced the rear suspension spheres on the 6.9. One had burst resulting in a very bouncy ride over the awful roads in London (and the UK in general). The last time I changed all spheres was back in 2006 or 2007. Many miles under the belt since. Interestingly the new ones don't come with red (front) or green/blue (rear) colour markings.

While I'm under there I will also be replacing the rubber donut between the propshaft and the diff. The spheres and donut with bolts are supplied by https://www.niemoeller.de/en. The diff back seal is leaking. I will need to to reseal the back cover and refresh the oil. When I rebuilt the diff back in 2002/3 I used Castrol B737 oil for ZF Limited Slip diffs. I still have a full can knocking about somewhere. It's so good to hoad :)

Also the fuel pump needs replacing and of course the filter, and any old half rotten fuel hoses. The pump works great in winter but in the summer when it gets hot the whine gets very loud. I'm afraid it'll fail on me one day soon so best act now.

Otherwise Mohan is in great shape. A joy to drive each time we go out. Not bad at all for a 43 year old.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: adamb on 23 February 2020, 05:20 PM
Here are some pictures of the donut, the fuel pump assembly (dirty!) and the diff (filthy and fuzzy!)

Title: Re: New 6.9 rear suspension spheres and other work
Post by: daantjie on 23 February 2020, 06:45 PM
Might want to take a look at the high pressure hoses on your struts as well.  If they are original to the car then for sure they need to be flipped out.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: rumb on 24 February 2020, 10:30 AM
Looks like great preparation for more driving later on. Note that the front and rear spheres are different whether marked or not.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: Punker on 24 February 2020, 03:50 PM
I did the same things on my 6.9. On the fuel package I think it is very important to replace all tubes; they were in a really bad shape on my 6.9, almost dangerous. Good work. Have fun.
Björn
Title: Re: New 6.9 rear suspension spheres and other work
Post by: adamb on 24 February 2020, 06:00 PM
Good point regarding replacement of hydraulic hoses. I'll look into it. I had the main hose from the pump to reservoir remade at a hydraulics shop for a mere £25. Saved a tidy amount over Mercedes prices. I'd imagine the same is possible with the high pressure hoses or is it worth replacing with originals?

For the propshaft bush or donut as I call it, can anybody please confirm the direction that bolts should go in? I alternated them in the way you see in the picture but not sure that was correct. I couldn't remember how they were prior to disassembly back in the day.

I expect to change all rubber fuel hoses. I imagine they are all 43 years old. Regarding the fuel pump - here saving money makes no sense as I expect the replacement to last well into the years that buying 95/98 octane petrol becomes a relative rarity.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: daantjie on 24 February 2020, 06:18 PM
For the flex disk, the nuts go at the diff/trans end from memory, however not 100% sure to be honest. Lots of posts online on other forums too, like W126 peachparts as well as Benzworld, as the methodology is the same across many models 116 126 107 etc. Make sure you place the washers correctly, there is only 1 right way to do this.  Wherever you have a "raised" section, you do not place a washer underneath the bolt head or nut.  Washers only go against the "flush" portion, if that makes sense.

For the hoses, these are pretty specifically specced hoses, and to my knowledge NLA from Benz. I think member "tcj" sells NOS ones.  As long as you match the inside diametre and pressure spec you "should" be fine to have these fabbed up, though they carry some pretty heavy pressure so you really need to be sure of what the hose can do.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: Jed on 24 February 2020, 07:24 PM
the hydraulic hoses are available as a rebuild kit from 'uncle kent' as well.
https://mercedessource.com/store/self-leveling-suspension-sls-high-pressure-hose-replacement-kit-w-instructions


Title: Re: New 6.9 rear suspension spheres and other work
Post by: gavin116 on 25 February 2020, 02:31 AM
Hi Adam
Great to see Mohan gets year round use. Pity Mrs White live 60 miles from me...


Attached I have a picture of my flex discs for reference.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: Randys01 on 25 February 2020, 03:39 AM
Wow!.   how clean is that under carriage?! Note the alloy trailing arms................cast steel on the 6.9 which defies the laws of sprung versus unsprung weight!!...curious as to the weight difference.
This issue arose in another debate/thread about converting 6.9 hydra to coil springs and shockers.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: daantjie on 25 February 2020, 11:23 AM
Indeed, a picture paints a thousands words, as they say, and it confirms what I said, just a lot better to see a pic ;)
Title: Re: New 6.9 rear suspension spheres and other work
Post by: revilla on 25 February 2020, 03:07 PM
Quote from: gavin116 on 25 February 2020, 02:31 AM
Hi Adam
Great to see Mohan gets year round use. Pity Mrs White live 60 miles from me...


Attached I have a picture of my flex discs for reference.

That's indeed a clean car... a pleasure to admire... looks rather a picture of a new car at the dealership in 70's... well done
Title: Re: New 6.9 rear suspension spheres and other work
Post by: rumb on 25 February 2020, 03:18 PM
Quote from: Randys01 on 25 February 2020, 03:39 AM
Wow!.   how clean is that under carriage?! Note the alloy trailing arms................cast steel on the 6.9 which defies the laws of sprung versus unsprung weight!!...curious as to the weight difference.
This issue arose in another debate/thread about converting 6.9 hydra to coil springs and shockers.


6.9 are Aluminum painted black.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: Randys01 on 25 February 2020, 05:58 PM
Well I'll be battered on both sides. :-[ I have been under the long held [mis] understanding that the 6.9 trailing arms were steel to handle the extra torque. I have read this more than once in my travels so it's not my fabrication.
I've not had need to work on the rear end [yet ] so never had the opportunity to corroborate this matter.
I will be under that car the moment I get it back from storage!

I've never had occasion to doubt there was a difference.  When we see other 6.9 bits beefed up but not necessarily well documented it sort of made sense that the arms were beefed up too. Classic example is the front suspension upper control link which is steel over alloy.
huh!

Title: Re: New 6.9 rear suspension spheres and other work
Post by: adamb on 25 February 2020, 06:25 PM
The trailing arms on Gavin's 450 look like the same kind as mine. Not sure if they are silver or not as the car does indeed get used in varied weather. I can't vouch for the metal they are made from but given the absence of corrosion I'd speculate aluminium.

Not sure I'd want to drive Gavin's car on dirty roads. The underside doesn't stay that pristine for long.

I'll be looking for parts in Europe and the UK.  Thanks for Mercedesource recommendation but it's too far out.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: rumb on 26 February 2020, 10:02 AM
Quote from: Randys01 on 25 February 2020, 05:58 PM
Classic example is the front suspension upper control link which is steel over alloy.
huh!

6.9 front upper control arm is also aluminum.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: daantjie on 26 February 2020, 12:11 PM
Quote from: rumb on 26 February 2020, 10:02 AM
Quote from: Randys01 on 25 February 2020, 05:58 PM
Classic example is the front suspension upper control link which is steel over alloy.
huh!

6.9 front upper control arm is also aluminum.

I think they were steel from the factory if my memory serves.  I replaced mine with some Lemforder ones, and I think you can now only find the alloy ones, though I stand to be corrected...Part number 123 330 4606/4707 for LHS/RHS
Title: Re: New 6.9 rear suspension spheres and other work
Post by: gavin116 on 26 February 2020, 01:24 PM
Sadly Adam, the underside no longer looks quite so pristine. I do use the car in all weather, and it has done two France trips since that suspension works were done. Those trailing arms were stripped and then repainted silver just to be a little different. Apparently if you bought replacements from Mercedes they were 'raw aluminium'. They were originally sprayed black from the factory.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: TJ 450 on 27 February 2020, 07:04 AM
The original 6.9 upper arms are cast iron although quite a few would have been replaced by alloy ones now (mine included). I have two sets of cast iron ones around.

The procedure for the rear trailing arms was to paint them prior to assembly/ fitment.

6.9 trailing arms are cast alloy like the 450SE/L and the upper end W126s. Lower spec cars had welded steel sheet metal arms.

Tim
Title: Re: New 6.9 rear suspension spheres and other work
Post by: Randys01 on 28 February 2020, 03:22 AM
The original 6.9 front upper control arm was steel. I bought the last one some years ago. Alloys were used on the lighter models..now very avail from anyone and everyone and doubtless finding their way onto 6.9's as the only viable option. Situations like this make me wonder where one stands in an Insurance Claim. 

Title: Re: New 6.9 rear suspension spheres and other work
Post by: adamb on 29 March 2020, 04:01 PM
The fuel pump replacement task is completed. Phew.

I started the work on changing the propshaft coupling, i.e. the rubber donut connecting the prop to the diff. But sadly I've had to give up. The last time I had the coupling off was a long time ago when I took out the diff. I tried disconnecting the diff from the suspension assembly today but got stuck. The diff body is mounted under the rear suspension assembly with 4 nuts. I could not undo one of the back ones. I just can't get enough force onto the spanner while lying under the car. It's very tight under there. I wonder if I did it up too much when I was reinstalling the diff... Anyway, I'm going to have to give this job to professional mechanics. As a matter of interest, I assume that it's possible to replace this coupling by lowering the prop. Is that right?

Title: Re: New 6.9 rear suspension spheres and other work
Post by: daantjie on 29 March 2020, 04:47 PM
To remove the flex disk you must of course remove large bolts connecting the prop shaft to the diff, then you need to pry it off with a long lever.  The prop shaft telescopes and by undoing the large collar nut you can make the shaft collapse into itself which gives more room.  Doing this on the ground is very hard, and you pretty much do need a lift for this job.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: ptashek on 30 March 2020, 12:18 PM
Quote from: adamb on 25 February 2020, 06:25 PM
Not sure I'd want to drive Gavin's car on dirty roads. The underside doesn't stay that pristine for long.


It's not that bad actually. Goldie still looks pretty clean despite now nearly four years and 16k all-weather non-winter miles on the road post-resto.
The semi-transparent wax it's coated with all-over underneath does slowly, but surely, accumulate stone chips which I patch up once a year, and road grime on the surface so it'll get manky with years for sure. Doesn't matter as long as it keeps rust away :)



Title: Re: New 6.9 rear suspension spheres and other work
Post by: rumb on 30 March 2020, 12:31 PM
I suppose a factor in bottom side cleanliness is how wet or dry the roads are where you live.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: adamb on 30 March 2020, 04:45 PM
Quote from: daantjie on 24 February 2020, 06:18 PM
For the flex disk, the nuts go at the diff/trans end from memory, however not 100% sure to be honest. Lots of posts online on other forums too, like W126 peachparts as well as Benzworld, as the methodology is the same across many models 116 126 107 etc. Make sure you place the washers correctly, there is only 1 right way to do this.  Wherever you have a "raised" section, you do not place a washer underneath the bolt head or nut.  Washers only go against the "flush" portion, if that makes sense.


My replacement flex disc has this handy picture showing the direction of the bolts. I no longer recall how they were fitted back when I first had the diff out so I fitted them the same as in this pic.

Title: Re: New 6.9 rear suspension spheres and other work
Post by: adamb on 30 March 2020, 04:59 PM
One more task while the back of the car is in the air is to change or top up the diff oil. The drain bolt on mine is seized. No amount of hammering would move it. The only way to drain would have been to remove the rear diff plate. The oil was changed only 18K miles ago and the oil still looked very fresh. So I decided not to bother draining.

Top up was achieved with this handy purchase from a local motoring store.. This cheap hand pump refills your diff with oil in a few minutes.


Title: Re: New 6.9 rear suspension spheres and other work
Post by: rumb on 30 March 2020, 05:02 PM
o I recently found that an impact wrench made quick work of removing drain and fill plugs.
Title: Re: New 6.9 rear suspension spheres and other work
Post by: ptashek on 30 March 2020, 07:45 PM
My trick is to wind some PTFE (plumbers) tape on the plug threads, minimising the chance of seizing, and leaks too. Never had any issues with it.

Adam, what's the name for that pump? Might check my local Halfords if they have one.
I did it the hard way a couple weeks back, won't ever bother again :D
Title: Re: New 6.9 rear suspension spheres and other work
Post by: daantjie on 30 March 2020, 08:26 PM
I also had a major wrench dance with the drain plug.  Had to resort to drilling and easy out.  It was nasty but I got my man ;D
Title: Re: New 6.9 rear suspension spheres and other work
Post by: adamb on 31 March 2020, 06:27 AM
Quote from: ptashek on 30 March 2020, 07:45 PM
My trick is to wind some PTFE (plumbers) tape on the plug threads, minimising the chance of seizing, and leaks too. Never had any issues with it.

Adam, what's the name for that pump? Might check my local Halfords if they have one.
I did it the hard way a couple weeks back, won't ever bother again :D

I have an impact wrench but not with me at the time. I used the old fashioned technique of a spanner and a large hammer. It still wouldn't budge.

I also uses boss tape white for threads. It's a smart move. Stops leaks too!

This is the pump I bought : https://www.halfords.com/tools/hand-tools/automotive-tools/laser-multi-purpose-mini-pump-121841.html