Bad head gasket or cracked head. If you continue to drive it you will cause serious damage to internal engine parts.
The 1999 Saturn engine uses dexcool type coolant. This coolant is different form other types and cannot me mixed with another type.
Engine Coolant Temperature Sensor.
need to change more often
Yes; it's on the coolant reservoir. The entire coolant reservoir on the Saturns is pressurized.
1993-2000 ide go with 1994-1999 somewhere in there would work nicest
usually 2 gallons of 50/50 does it
On my 97 SC1, the vent is a tube between battery and firewall. Not sure if the same on the SC2.
Dextron III fluid is the only requirement
Saturn is a good car except for seat belts are designed improperly. They can choke you, if you don't adjust them.
1.9 liter dual voerhead cam 16 valve
Have it scanned to determine problem
The PCM is inside the dashboard, to the right of the glove box.