Buying a G? Things to watch out for: Rear Shock Perches (All models)
Summary:
Corroded rear shock mounts are common on earlier (80s) W460s and will likely become a more frequently encountered problem on later 463s as time goes on because the design has remained substantially the same. Worse on UK vehicles that are subject to road salt.
Corrosion starts with the forward 'cup' (top of the damper bolts into), progressing through the front mount (70mm tube) and onto the top spring mount. NS rot is most common, but if its there then DS is likely to also need doing.
Its usually easy to spot, though bodges involving MIG filler, a covering of chassis paint (and mud!) can cover a multitude of sins.
Unless it has failed you probably won't experience symptoms when driving (though they can creak just before failure!).
If the front cups are in any way corroded then you should carefully clean off the tube and upper spring mount to see the extent. If there is any corrosion at all of the upper spring mount expect to replace it. Beware that it also often corrodes around the backside rather than the outward facing front and water gets inside it to corrode it from the inside-out - see pics!
What is the bad news?
It can be (extremely) expensive to fix. Caught in time, a procedure to cut out and replace the chassis mount points can be done in around 6 hours without removing the body (lifted on loosened off bolts). Best case involves replacing (cutting out and re-welding) the front cups (about £150-£200 @2012 MBUK prices). TIP: Be very careful doing anything involving heat, spark or flame so close to the fuel tank!
If left too long though, the mount often experiences catestrophic failure, typically tearing some or all of the front chassis support tube off.
To fix this properly is a body-off, many hours task on the ramp involving cut back and re-fabrication of the 70mm front support tubes (tip: upgrade to 5mm wall seamless while you are at it!) and replacement of the cups and upper spring mount. Around £350-£500 in parts and materials (2012 prices), but its the labour involved that is the deal-breaker. Once done, its good for 30+ more years.
When should I walk away? Any substantial rot on the perches and you should negotiate a heavy discount (000s) and be prepared to sort it or walk away. Remember that unless you are up to doing this work yourself (a decent 200A Mig will be required) then labour is the killer (and you'll need an engineering shop that is up to the prep and welding.. don't count on your ususal 'parts-swappers' to take this one on!).
And, unlike most body work rot -if this fails, the vehicle is off the road!
Thought I'd investigate a hole in the N/S spring seat after reading this and found that it will need replacing rather than repairing, it certainly won't go through the next MOT. I gave the shock perches and tubes a good clean up and they appear to be sound as does the offside mountings.
Does the body have to be removed altogether to replace the spring seat or can enough clearance be gained by slackening the bolts and jacking it up a bit? The body already has a 2 inch lift. I guess it would also be safer to remove the fuel tank before starting?
Trying to weigh whether to attempt this myself or to get it done by a garage. I have a friend with an engineering shop and who is very handy with a welder.
Going the other route, does anyone know of a garage in the north of Scotland that they'd recommend to carry this out? J R Weir in Inverness have been bought by Arnold Clarke and no longer have a comprehensive bodyshop.
Great guide by the way!
Cheers
Dougie
you couldnt send those photos to me in the original format and high res could you ?
Two weeks after I bought mine I discovered this rather noisily As I had an RAC report done before I bought it and they missed it, they paid the replacement costs
Ouch - that's a 463 too - I know I shouldn't ask a lady her age, but what year?
It does illustrate the problem though - beneath the crud and muck (and even below an outwardly OK looking top surface) it can be difficult to spot which is why you need to clean them off when buying a G of this age - if the seller isn't happy to do this....
My photos? sure - what did you want to do with them?
It is 1993. Trouble is, they are real mudtraps and don't clear out unless you do it manually. I have since been told they are a realy weak spot on them so your post is a very good one.
The seller was happy to let the RAC man do whatever he wanted- he even had to go and collect him from the main road as he said that Health and Safety concerns wouldn't let him come down lanes like that in the snow in his van!! I honestly don't think he knew about them either as he pointed out all the faults he know of.
You are right - I think if they are cleaned there isn't too much of a problem (when they are re-done though, stripping off MB black zinc coating and respraying with POR15 or similar is a good move though I think).
I'll be in your neck of the woods this weekend by the way - some land in Liss with a Roe problem to look at on Sunday - I'll wave if I see you :-)
I did spring mounts top and bottom at the rear by lifting body in place the required 3". A plasma cutter would be nice but did it with 4.5" and 9" angle grinder (really only the small one is required). The top shock mount was actually OK but not perfect.. the spring mounts have unprotected paint wise surfaces that just rot from the inside.
Axle stand + 9" blocks for chassis, dropping axle (but not taking off swing arms, jacking body up but resting on wood wedges between body and chassis is not real pretty and you need to be a bit careful but it can be done DIY on a nice flat (and preferably covered) hard surface..
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If the structure of the chassis (being the perch mounts i.e. tubes) is not in question then my guess - having done the work shown in my post myself I think is that it is something you could do do a fair job on with the body jacked up.
That said, clearance will be a challenge if you want it to look good (I think it would be difficult to get the MIG angle for the topside weld) even with a 2" lift (which is what I also have on my vehicle). Not impossible, just more challenging. If you know someone who can weld then I'd get them to do it (professional MIG is the way to go) as you don't want to be second guessing weld penetration and quality on this as you go.
This is supported by some of the posts I have seen elsewhere where this technique has been used. Plasma cutter is the way to go to remove the old mount by the way.
Structurally it would be OK (providing the welder gets the penetration right), then as they say 'would be good enough for farm work' ;-)
Re. Fuel tank - your call. Diesel and I'd wing it (my old diesel tank was upgraded to plastic at the same time, so I just emptied it and thta was that. Petrol though is another matter.
Plastic tanks melt/ get cut through in a second, metal tanks rust and weep. I suppose that there is an argument to say that if you do it with petrol, then a full tank is less likely to go bang than one full of vapours!