Exact same thing happened to me last week, tried reinforcing it with a copper pipe on the interior, tight fitting, with JB Weld, held for a few days then started crumbling in other places. The small hose to the reservoir cracked off two days later. It was just self destructing. Best place to buy a radiator is
www.radiators.com. For my car '91 560 SEL price was $199, no tax, no shipping, lifetime warranty, ordered 2:00 P.M. Monday arrived 11:00 A.M. Tuesday, no charge for shipping or next day delivery! NISSENS brand made in Denmark.
'91 560 SEL 88,000
'94 SL500 22,000
'86 300SDL 202,000 fire wreck