engine overheated does the engine need to be replaced?

way i see you don,t have replace motor unless got front end knock sounds to me might be something else doesn,t sound to serouis nothing i and got a problem with

Check and see if the two fans are coming on when the car reaches temp around 225. These fans are in front of the radiator. Check on line and see what the correct temp is .

If the coolant level keeps going down but can't find any leaks it may be a bad head gasket due to threads in cylinder block giving out. This a common problem with the 97 deville 4.6L. I have one and had to remove the engine and repair the threads in the block just after I bought it. It is no fun taking the engine out, but since I did the job it has run great (about 40,000 miles) with no more overheating.