powersteering pump wine

[ConstantFix]

owner of a 87 SR5 4cyl. 380,000km original p-steering pump. it now wines like a little B**CH but has plenty of fluid and doesnt leak any. could it have possible become clogged? or the impeller worn out?

 

[Stick Figure]

I don't have much experience with the earlier gen 4runners (check in 1st gen area for that), but I've had other Toyota's of the same era that had the screen in the bottom of the reservoir become clogged over time and cause issues. I would probably start by pulling the reservoir and cleaning it out.