Just turn the wheel one way about a full turn of the steering wheel and remove the drain plug. The steering box won't drain in the center position, but you don't need to go far to get to an open position on the working piston.

Please get another person to fill it back up. You want to fill the reservoir as high as you can (engine will jostle it a bit and might spill), then have someone sit at the wheel and start the engine. The wheel needs to be turned from lock to lock moderately slow while someone else fills the reservoir back up. You don't want the pump to run dry.

Lock to lock twice should be more than enough to bleed the system.

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Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

I’ve always performed this procedure engine off, but you know these boxes well.
I’m curious why you suggest doing this with the engine running?

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1981 240D 4sp manual. Ivory White.

You want to fill the reservoir with the engine off. You turn the engine on to have the pump fill/bleed the system. With the engine off there's no fluid circulating around the lines or the box.

__________________
Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

Isn't this achieved by turning the wheel from side to side? manually articulating the gears?

When I do this, I turn the wheel, fluid drops, turn again, and repeat (usually three complete turns) until the fluid no longer drops. Top off, fin.

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1981 240D 4sp manual. Ivory White.

Sure, you'll get a good amount of fluid in, but you aren't priming the pump or forcing fluid into all the passages in the box. Its like an oil change without running the engine after filling, or a coolant change and not running the engine.

__________________
Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

Remember to replace the PS filter. Never had much difficulty bleeding those PS systems. Put the wheels in the air and turn side to side slowly.

Removing the drain plug at the box is interesting, learned something...thanks!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Gotcha -thanks for the explanation

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1981 240D 4sp manual. Ivory White.

You do not really have to jack the wheels off the ground but it is certainly easier on the rubber. Either way it will prime if you go lock to lock a few times and keep the reservoir topped up. (Yep, I ended the sentence with a preposition. But I am reading an excellent book called Carpe Diem, Put A Little Latin In Your Life by Harry Mount and am getting more comfortable flaunting tradition.)