Didn't these cars have an oil cooler(or transmission cooler) built into the rad that often leaked.

That was Toyota Landcruisers !

And MB's with Valeo radiators, from around 98 to 04 if my memory serves, coolant ends up in the auto box effectively destroying it, best course if a Valeo rad is fitted is to replace asap before this happens.

Not easy to spot it happening if you have a sealed for life box from that era (pause for guffaws of gallows laughter whilst pointing at whatever twerp came up with that gem) with no dipstick to check the gear oil and a sealed dipstick hole...by the way MB, and i'm sure all the others, quietly dropped that silly marketing gimmick a few years later when it became apparent that sealed for life meant a not long life in many cases...the specialist indies never believed that tripe anyway and continued servicing auto boxes despite MB's fashion statement of the time.