I have an '86 240 that generally runs great but after I have been driving on the the highway for a bit the steering begins to "groan" when I comes back down to normal street speeds (20-40 MPH). The power steering fluid level is fine; the groan seems to get worse as you acclerate too. Has anyone else experienced this or heard of the problem at all? Could it be the pump?

 

Could be a bad steering pump.