I have about 166,000 mi. on the original power steering pump. Just recently, when first starting the car, and reversing, the steering response feels "heavy and sluggish" while turning the wheels. I did top off the fluid level last night, still the same problem. Heavy and sluggish, maybe it's more of, like having one or both of the front wheels with 15#'s of air in them while trying to turn the steering to either way.

There are no leaks, cap was on tight, no noise, belt tension seemed good.

Once the engine has warmed up (after 10 miles or more), it works fine, but after letting the engine cool down for more than several hours, it will exhibit that same problem again. Maybe the fluid needs to be drained out completely?

Rack and pinion? But no leaks anywhere?