1999 cadillac sedan deville and it keeps showing temperature of 200 plus but car is running smooth!! this temp reading scares me what could be the cause!!

Some thing too check:

Make sure coolant level is up to line and clean (not dirty, may need to be flushed out).

Make sure air flow through the out side of radiator is clear (dirt, leaves, ect..) .

Make sure electric fan is working properly (not running slow).

Check radiator cap, (no gasket tears).

Could be thermostat going bad ?

Could be coolant temperature sensor/switch (from computer) going bad?

Check radiator hose(s) (too soft, may collapse)?

ECT.............Hope tis was some help??.