Steering hard around any small corner

I have a Toyota highlander 04 that's having trouble steering, it's really hard to move the wheel. I've checked the steering fluid and it's full, a family friend mechanic also looked at it, and replaced the power steering pump thinking that was the problem. But it was not, it went on and off steering hard around corners, extra hard when you first turn it on, and even after a second replacement pump it still remained to do so. But now it's hard 24/7 not just half the time.