One problem related to wiper has been reported for the 1999 Buick Century. The most recently reported issues are listed below.
I had to replace the head gasket twice. Mechanic indicated the first time that the coolant might be the cause for the gasket deterioration. When replaced the second time, the gasket was (I believe) a metal rather than plastic or rubber and the coolant was green. So far, so good. Both replacements cost $1000+. Recently had brakes replaced and was told the intake manifold gasket needs to be replaced at a cost of $1100. The car runs well, but has serious rust on the rail below the doors. Not sure I should spend that much on a 16 yr old car. I've also had to have a motor on the driver's side window repaired. That seems to be a frequent problem with this model, too.