[MBZ] Pwr Steering Groaning

[Rich Thomas]

The last couple of weeks the PS on the 79 TD has been groaning a bit on 
turns.  I changed fluid/filter 6-8 months ago, no problem then.  Fluid 
level OK, no leaks I can see.

It has been a bit cooler here (like 40s low a couple nights, but 70s-80s 
in the day) but it does not seem to be temp dependent -- does it when 
the car is warm in the daytime.

What might be causing this?

--R