Thanks for all of the suggestions. I am going to California to visit her and I will have a chance to check it out for myself. I guess I'll take a stethescope with me to see if I can figure out where the knocking noise is coming from. Are there any other ways I can tell if it is definately a rod knock without disassembling much?

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1987 300SDL 167k
1992 Volvo 740 140k
1990 Volvo 740 250k
1989 Volvo 240 269k

Anyone want to trade an old Volvo for an '87 300sdl?