Power steering?

It is either you belts, pulley tensioner, or your power steering pump. Good job on buying a great American made car. Cadillac is a luxury car. Good luck.

Sounds like your pump is siezing up (freezing), this will load the engine and make it idle oddly. If you have to add fluid where is it going?. Get it checked out by a competent mechanic right away!. If the pump quits suddenly that could be very dangerous indeed. Good luck!

Could be a power steering pump or a rack and pinion. If the noise is coming from the power steering pump or drive belt, you probably have a bad pump.

you have a leaking pump. the weird idle maybe caused by the pulley on the pump is worn thus leaking fluid. have it fixed ASP or when the belt breaks or the pump fails it will cost you more to fix later

your losing fluid someplace and causing your power steering pump to run low or dry and making it growl, you either have a broken hose or the rack itself is leaking, take it in and get it checked before you ruin your power steering pump.

sounds like your pump is going out. i have a 93 cadillac seville and it is doing the same thing. the pump (on mine at least) has decided its time to give out. having the pump replaced should clear that right up