How much fluid should be put in the resovoir?

Mine has a little gauge with a min-max level on the
center stem. At the max, the resovoir is about
1/3 full.

Is there any problem with filling it to the top?

Also, if I have ATF in the resovoir and I suck it
out can I put the MB fluid in eventhough there may
be ATF further down in the system?

93 300SD -165,000 miles

Thanks.

Does your owner's manual say to use MB specific fluid. Mine says to use regular ATF. Now granted our cars are 13 years apart, but I would think it would still be the same. Is this MB fluid you are putting in, is it MB ATF?

Mine says to use MB Power Steering Fluid.
Fluid should be between the min and max.
As for mixing, I don't think there would be a problem, but I'm not 100% sure.

I'd try draining out the ATF. Take off the return hose and let it puke into a drain pan after starting the car, then reconnect and fill and bleed with the correct fluid. I don't know what harm would come by overfilling the reservoir. As a general rule, I'd put it where it belongs, no higher than MAX. Is it losing fluid THAT fast?....Gilly

I am not losing fluid other than, possibly, a little
sweating down below. I used to use a little fluid but
nothing in the last six months or so.

The reason for the fluid question was that I had
a steering problem twice - both times when the
ambient temperature was in the low to mid 90's.

The problem was that I would get a little noise
and vibration when turning right (the second
occaison it was left and right) as though something
was slipping or binding. It would do it when the
car was still and at low speeds. At highway speeds
it was fine. These incidents were about 3 days
apart and has not occurred in a week.

I am concerned about the pump but I checked and I
have no fluid loss.

Most of the postings have advised checking and changing
the PS fluid.

BTW, how do you bleed the PS pump?

-Ralph

Check your hoses. They do get old. If they are "wet", replace them. You may also check all the hose connections. I replaced my return line and I did use ATF, although my car is older than yours...it has been a couple of years, no problems.

Ralph: If there is no fluid loss, why is this even a concern. If it has ATF in it, how'd it get in there if there is no fluid loss? What model is this? The 300SD and 93 make it sound like the 350SDL, with the 605(?) Diesel in it. At any rate, the earlier year V8 140 chassis did have a big leaking problem. There is a hose that connects the reservoir to the pump itself, those connector hoses were a big problem, still get one once in a while. I don't know if your engine has this arrangement or not. I know I may be off on my model designator, it may say 300SD on the decklid, it was hard to keep up on model designations in the early 90's, seems like there was a new designation for the same vehicle every year!.......Gilly

The car is a 1993 300SD, which is the 3.5 liter 603.971
diesel engine.

What brought the fluid issue was that fact that twice,
at 902+ degree ambient temperature, I had a problem
steering at low speed or when the vehicle was stopped.
The steering wheel had some vibration coming through
it and a sound like something rubbing, etc. ( the
sound is hard to explain).

Most of the postings and advice have suggested
checking the PS fluid, which is between the min
and max in the resovoir. However, the resovior
is only about 1/3 full.

On the level, I believe there are 2 "steps" at the bottom of the plastic piece that is on the stud in the reservoir, there are temp markings on each step. If the fluid is above the low step and below the high step, you are fine. Is the steering gear box leaking at all?
Gilly