Same problem . . .
Had same problem with '91 2.3 190E. My tech said that this is a common occurrence with that car. I believe MB had a recall for cars that were within 50K miles. Mine was beyond that.
Found a mobile welding service that came to my tech's garage and welded it. Crack was slightly visible from the top but wrapped around under the header. Had to be done on a hoist.
The welding worked perfectly. Cost about $75. I elected to do this because it was a 'quick' fix. Didn't know if it would hold but it did.
One suggestion: Remove the O2 sensor because mine died after that operation.
Regards . . . . JimF
'94 S500 Cpe
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