Thanks Paulwho,

I guess that is a solution. I'm pleased I managed to find the correct pump that did not need this mod, though. These cars have enough potential places for coolant to leak without adding more! Most repairs to my family's and my MBs involve the cooling system in one way or another. Water pumps, radiators, expansion reservoirs, thermostats, temperature switches, O-rings and fittings, hoses, heater valves and I guess head gaskets since it seems to be corrosion that affects them. Yes, I do use genuine MB coolant. It finds its way out everywhere! You cannot afford to have faulty cooling systems in the Aussie summer temperatures we have at the moment.

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.