For those models with the standard Mercedes rear trailing arm suspension there are numerous reports of the arm cracking and collapsing. If this should happen at highway speeds you could lose control of the car! This applies to the following chassis: 114, 115, 107, 116, 123 and 126.
Problem & Solution
Common among these chassis:
Failure is almost always due to rust caused by the car being driven on salted roads. The rust usually occurs from the inside and works out. It is very hard to see and will usually show up first as cracks around the lower rear shock mount. If your car has been exposed to road salt in the past or you find evidence of severe rusting under your car then you need to closely inspect your trailing arms and keep an eye on the in the future. If you are not sure what you are looking for then take your car to a good suspension shop for a thorough inspection.
The only solution is to replace the trailing arm with a good used one. Be sure to purchase one from an area that does not use road salt or where the climate never sees snow... :-) We do carry good used trailing arms for the 123 chassis and from time to time we get a few in for the 126. See related products below.
When changing out a trailing arm we recommend you replace the trailing arm bushings, the center differential rubber mount and the rear subrame mounts. In most cases it is also a good time to replace the emergency parking brake shoes.