What are the symptoms of the main bearing going out?

[Phil Payne]

> My 91 200 20V has a knocking coming from the oil pan. Actually sounds 
like something is hitting it from the inside.  The sound has a patter of 
three quick knocks followed by a second or two of no knocking, then 
repeated again. Is this a sign of the bearing spinning?

Oil pickup pipe has come loose?

I'd advise dropping the sump pan IMMEDIATELY.  If that thing really comes 
loose, it can snap conrods and puncture the block and sump.