I have a 1993 Saturn SC 2 door Coupe. Just a few days ago i began to notice a rattling noise that is constantly on no matter the gear or speed. It is not extremley loud but it is noticable. What could it be / how much will it cost to repair ?

Also i have had to add engine coolant about three times over the last week and a half. Is it a leak as i suspect or could it be something else?