-fad.. what MB dealership told you is correct. mine is '87 200 with 450000 km on the odometer. for the last 100000 kms i suffered those squeaks from both A-pillars. there are two sections welded to each other and they might lose their rigidity related to rough surface driving, consistent potholes, etc.. i had them welded (windshield not removed) and squeaks are gone. many W124 owners suffered that around here so it's pretty common fix.

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2001 E200 Kompressor Avantgarde
1987 300E 5-speed
1976 450SLC
1975 280S (sold)
1973 230.6 (sold)