Mixing the new red antifreeze with the green can cause it to look rusty and will form a sludge. If someone is topping off your antifreeze recovery tank during oil changes with the wrong product could be one cause.
Intake manifold gaskets are leaking, intake manifold is warped.
Your intake manifold probably has a crack in the water jacket.
Heater hose or heater core.
locate blend door actuator for 1997 pontiac bonneville se
According to the 1997 Lincoln Town Car Owner Guide : ( it came from the factory with antifreeze that meets Ford specification ESE-M97B44-A ) * that would be green color antifreeze *
How much antifreeze is in a 1997 Honda crv
A 1997 Jeep uses the regular green antifreeze.
According to the 1997 Ford F-150 owners manual : It would have come with green colored antifreeze from the factory ( meeting Ford specification ESE-M97B44-A )
The Autolite website lists a gap size of .060 the 1997 Pontiac Bonneville.
The generator or the alternator
The gas gauge sending unit would be located in the fuel tank.