It could be multiple problems. check your coolant level, it could also be your Lower intake gasket or even a head gasket.
The cost to replace a head gasket in a 1997 Buick Park Avenue ranges from $20 to $180+. This varies based on brand, store and labor costs.
Procedure to change 1988 Buick regal head gasket
Replacing the head gasket on any vehicle is a long and complicated process, however if you wish to see basic step-by-step instructions go to the related question on the right side of the page "How do you replace a head gasket?"
take off the head, replace gasket. reinstall head
The head has to be removed on the 1993 Roadmaster to get to the gasket. You will need to remove the intake, exhaust manifold, and valve cover then unbolt the head to remove it. Check the head for warpage while it is removed.
some general causes: leak in cooling system (including possible blown head gasket) resulting in loss of coolant; defective thermostat
replace head gasket
Remove head change gasket and replace head, pretty simple.
What is the cost to replace the head gasket on a Mazda MPV?
cost to replace a head gasket
The 1994 Buick Century 4 cylinder head gasket will have to be removed and replaced. The head has to be removed, along with anything that is physically in the way of removal, before the head gasket can be removed.