This doesn't make any sense. Welds are coated just as the rest of the part is, so it isn't an issue of bare metal. And welds are stronger than the material surrounding it.

Metal fails NEAR the weld, as it did in this situation.

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Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

Agreed, I wasn't saying the weld fails, I was saying the metal near it fails. Apparently im not good with expressing my thoughts.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Metal oxidizes when welding starting rust.

Paint usually does not flow so well into the groove between the metal and weld bead.

Welds are often rougher than sheet steel so paint does not cover so well.

17 year old car in a snow / salt area. Don't blame the manufacturer, things wear out.

The problem IS with the design. But not just the W210, but also other modern cars, have had everything lightened up. On the W210 (we own one) the poor spring perch is a well known fault. Another is the beam that runs across under and near front of the engine. It is very lightweight and formed out of sheet metal. The plastic undercovers trap water and the beam sits in it. I had corrosion on that beam. Under their Goodwill program, MBCanada had the beam replaced for me (Several thousand $$ job)

Those control arms with corrosion on inside, likely look perfectly OK on outside. Ours (and the rest of the car) get annual external rust treatment. But inside, metal may be getting thinner and thinner. Eventually you hit a bump and it fails. When designing mechanical parts, designers should provide metal thickness required by design+safety factor+corrosion allowance. Perhaps they didn't think the metal would corrode from inside where it is not exposed to environment?

We have discussed W123 rear control arms before. I have one that is partly corroded. I drilled a few holes near top and sprayed in Fluid Film and then installed removable plugs in holes. Still OK but always a concern.

Sounds like our E320 control arms may need same internal attention?

On the positive side, after 17 years, we haven't had a failure on W210 suspension. Fingers crossed!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5