Well here's the update. I replaced the coolant pipe. The car ran fine for a day and a half. I am now back to squae one. I am having the same problem all over again. I am going to dig in again tonight. Will keep you guys updated.
2002 BMW 745Li 102k
1991 Mercedes 300D 2.5 turbo 338k
1993 Mercedes 300E 2.6 192
1995 Mercedes E420 160k