The weird thing is, though, that if I shut off the car and start it back up (even just 5 minutes later), everything goes back to normal for a while.
But once I am driving for say 10 - 15 minutes or longer, it starts making noise on turns and gets heavy.
I recently changed the pump to another used pump. This is the 3rd pump I have replaced in the last 2 weeks, could this be another bad pump (even though it doesn't leak fluid, as far as I have seen, and it doesn't have air bubbles in the reservoir)?
What are other things that could be causing this? I was reading up other causes of the general whining noise and some were suggesting replacing the pump inlet fitting O-ring, but I am not sure if that is the case here.
Is there any easy test I can do to see if it really is the pump inlet fitting O-ring in my case or if there is something else going on?