You neglect the maintenance here and you WILL pay the price
To avoid trouble like you will see in this video be sure to change (flush) your cooling system at least every 3 years. And only the proper MB coolant please!!
Problem & Solution
Common among these chassis:
Classic Sedans
Ponton
R107
W108 W109
W110 W111 W112 Sedan
W111 W112 Coupe
W113
W114
W115
W116
W123
W124
W126
R129
W140
W201
W202
W208
W210
W211
W220