When I got my first W115 (a '75 230) an experienced mechanic examined the car and said the radiator should be grounded. He said Mercedes had issued a bulletin that showed a wire from the drivers side on the upper corner of the radiator to the engine block, this supposedly prevents electrolysis. I made one up asap.
I don't know if this applies to the later Behr radiators, which are aluminum not copper and brass like the earlier rads.
I had a failure in a 300D (W123) when the rad neck cracked on a trip. I simply left the cap off and the engine didn't overheat (I watched the gauge like a hawk!) fortunately not a lot of uphill driving, and I didn't use the A/C.
I saw someone try to repair this kind of failure using epoxy, but it was futile. Iwas willing to pay say $300 for an all aluminum radiator for the W124 diesel but never found one. A specialty radiator shop wanted $650 to make one up (hey that's half the cost of a new head! I think I'll continue gambling with the stock Behr - reminds me~ HGV where are you? I need that Radiator!
DDH

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!