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6.9 repair underway - by east london hairy bloke.

Started by pal, 24 December 2011, 03:14 AM


Hi Guys,
I was expecting the engine to be out over Christmas but my mechanic ran out of time and left for sunny Jamaica (lucky for some). Since then I've been prepping up for some rustproofing and repairs around the engine bay and I've noticed that the area that I wanted welded once the engine was out is fairly accessible from the outside. Would it be better to cut and weld from the outside or take the engine out then weld up/repair the rust? My concern is that this bar is load bearing and perhaps should be replaced - is welding it a bad idea?

An engine in/out is £325 (no engine hoist
:( ) including stripping it - but excluding any repairs. Apart from these two areas, everwhere else is accessible. There is an leg/arm from the suspension that is bolted into this bar - both sides of the engine show that the bar that the bolt is tightened through is rusted up and has signs of previous bodgywork. Looking from above:
These bars are hollow and only a single layer, they are split three ways at the base and sit on the same part of the chassis. Looking from the sides behind the wheels:  So I thought I'd ask you guys which was the better route. I'm tempted to remove and refresh/restore the components behind the wheel anyway as they look a little corroded.I am keeping the car as long as I can so it needs to be a decent repair, my ten year old son got very upset when I mentioned it might be better to sell it! He said he wants to drive it :)
Thanks for any advice and seasons greetings to all!

TJ 450

That rust is a little bit nasty, I would try and get that whole section off a donor chassis if you can. The only problem is that the alignment will have to be dead on.

That is load bearing indeed.

At the very least, I would remove the control arms and determine the full extent of the rust.

1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500




Yeah, it is scary :o , I've been lying in bed at night thinking what I will do next or whether the £1500 spent on the rest of the welding by Goodmayes Autos was a waste..... I'll get the control arms off and the manifolds too. I have a small angle grinder I'll try to clean up with, once the surface sealer and grime comes off I should know how bad it really is.

My donor car is also rusted in the same area but not as bad, because the donor engine is smaller there is plenty of room to fashion a new section, I'm hoping to find an expert panel welder who can do a good job. So far I've had two that said they were coming but they didn't show up - I guess its Crimbo and only sad blokes are working on their cars - ha.

It has to be right so if anyone knows a good welder in east london please get them to call me on 07899793744, cheers all.


I removed the wheel and the control arm from one side, cleaned up to investigate and..... the area has been repaired previously from the outside. Welding looks a little rough but seams are strong and straight. The mess on the engine bay side turned out to be a botched cosmetic repair job filled over with sealer and paint.

So I showed it to my father who has several decades of metalwork experience and after some hammering and checking it is fine to clean up and treat/paint - apparently not a fine job but adequate and safe. The car did drive right beforehand so hopefully its good.

I intend to grind the engine bay sides of the bar to reveal the metal, treat it and then fill/paint - same on the wheel side. I've already started stripping the bay - some other horrid areas found but easy to weld up or fix.

Here are some pics, all opinions/advice welcomed - this is a new adventure for me.

s class

Well done with your progress.  Those new areas of rust you have identified are all standard W116 issues. 

[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


Ah you people in warm countries are soooo lucky! London is cold wet and miserable :-) Managed to get a tent up so its dry, even if it is still cold! :-)  I've been cleaning up and preparing for the welding work.

The rubber boot on this joint is broken and furthermore there is some sort of rubber washer/ring that was loose and broken.

Would it be ok to undo the ball joint and fit a new washer or does this mean that a part of the strut will need replacing?

Also as I have been cleaning up to search for rust I have found that dirt and grime/possibly some sealer have fallen off - should this be exposed? Or is it advisable to put rustproofer and sealer on it? It seems parts of it have been sealed in the past.

As always thank you for your guidance in advance, Cheers.


Impressive work. You are certainly very brave to tackle this job. Braver than me!
1977 450SE [Brilliant Red]
2006 B200


Thanks Mforcer, my friends/family & neighbours think I'm mad. But the car is just tooo good, I think its about as close as I've come to a relationship with something mechanical  ;D
Its great to have all the posts from the experts on this forum - you learn so much. My greatest fear is bodging it, but having no money slows me down and I have no choice but to take my time.

TJ 450

Nice work.

As far as I know the balljoints might not be available any longer, but it would be worth checking with the Classic Centre.

It might also be worth finding out from other car enthusiasts in your area who might be able to recondition ball joints such as these if they're NLA.

To remove the ball joint, you need to hold the "cup" of the strut somehow, and modify a 22mm spanner so that it fits the flats at the top of the ball joint (it screws into the shaft of the strut with the cup acting as a washer).

The whole process can be done, but is rather difficult and may damage the cup in the process. There's not a whole lot else that can be done though.

When I was assisting MT with the struts on his car, we just fitted a boot to the old ball joint after flushing it out as best we could.

The struts are simply NLA, but they are long lasting so it's not much of a problem IMO.

I see a 350SEL next to the tent... Very nice.

1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500


Thanks for the tips Tim, I've been in touch with a (Citroen) Specialist called Pleiades. I used them a few years ago to repair some hydraulic leaks I had. I've got some other Merc avenues to try but failing that it will be a case of flushing it and making good/seeing what else fits.

In case any UK boys are interested Pleiades don't have a site but there is a pdf floating around the net
They are based in Sawtry in Cambs - old school and very fair on pricing, before I went to them my 6.9 used to sag one way or the other.

Looking forward to the weekend.



Yeah that 350 SEL is a bit of an odd one, I didn't think there was any such thing as a 350SEL, I'd only ever seen SEs  ??? - maybe its an import? I bought if off a guy years ago for 700 quid. It had a broken manifold seal and perished exhaust but was otherwise ok.

TJ 450

The 350SEL is a very rare car, as only a small number were produced.

The Citroen specialist would be ideal.

1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500


In Australia it is possible to get those ball joints reconditioned but I think they are the same as the ball joint on the bottom of SLS struts so there should be a plentiful supply of usable ones available if that is so.

Congratulations on the work and yes I agree it is very worthwhile as there will not be many 6.9's in the UK soon.

The rust you have is standard W116 stuff as S-class says but we don't usually see this level of rust in Australia due to teh climate.

The upper suspension mount is often considered the final structural rust point and is the reason many cars are scrapped but it is actually stronger than it looks and your repairs should be quite adequate.

I think you are very brave doing it all in a tent in those temperatures but perservere and the rest of the journey should be easier.



Hi pal,

Good luck with your repairs. They are worth doing and are not as bad. Our Australian and American cousins can't appreciate how much welding we tend to do to keep cars going in the UK. My 6.9 has to have boot floor sections replaced last year as part of the reconditioning. Moreover it looked fine before they started stripping rust away. My 450SEL parts car also looked fine but it is actually rotten as hell. You should bring your 350 to the meet (see my other post).