450SEL Power Steering Pump Squeal (like a ...)
 

1980 450SEL with 158k miles. Doing the 75k majors and more.

Using a stethoscope with a probe I'm 90% certain I've isolated a moderately loud squeal to the power steering pump (manufactured 12/79 by ZF). Since I've not changed on the V-belts yet, I plan to remove the pump's belts to see if the noise goes away. I also have a leak somewhere in the pump area. Not a lot...yet, but it's getting messy.

I've done a search for this and found the instructions for changing out the fluid and to not use ATF but use power steering fluid (Thanks Larry Bible and MB Doc). I did probe gently looking for sign of a filter, but found none (manual is not clear if one exists for this pump or not, or how to change it). Did find about 1/32 to 1/16" of crud on the bottom. Left well enough alone.

Need thoughts on options:
- Swap out the fluid AND try and locate the filter.
- Pull the pump and replace the seals and clean it up
- Buy a pump from a dismantler (Potomac German is just down the road)
- Knuckle under and buy a rebuilt ZF

What else is there worth trying?
Can anyone tell me if there is a filter?

I'll probably be driving this car for at least 5-10 more years.