1990 Mercury Cougar power steering pump

It sound like a problem with your power steering pump I just fixed the same issue on my 92 cougar. Check you power steering fluid level. If its low, you may have a leak, have your hoses checked and maybe the pump itself. Easy way to figure out if yu have a leak. If the fluid is low, fill with fluid to the correct level, then put a piece of cardboard under the car. If there is red fluid on it the next morning your pump is leaking. Do not panic yet though, you may just need to replace the hoses. But get that done fast, so you do not end up ruining your pump.