Hi folks. I'm replacing the high and low pressure hoses for the power steering on my 83 300D tomorrow. Obviously I am going to have to remove the fluid. My question is, after refilling, is there a specific way to remove any air in the system, or should I just jack up the front end and turn the wheels lock to lock a few times?

Thanks for any help

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

That’s what I do.

Alternatively, couple pieces of cardboard under your front tires and skip the jack.

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1981 240D 4sp manual. Ivory White.

I suggest lifting the front end so the tires are off the ground

Remove the drain plug and turn the wheel stop to stop to get all the fluid out

When you refill for the first time, fill it to the top and replace lid and crank/run it for a second or so. You should about empty the reservoir. It will look frothy. Let it sit for a bit. Add fluid as needed then. It will work the air out but you need to let the frothy settle down to see where you are with the fluid level

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.

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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]

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.

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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]

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.)

Thanks all for the tips and suggestions. Hoses are replaced, system is bled and it looks like we are good to go. Not a difficult job, just a little on the messy side.

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

On a Dodge Cummins, the steeringbox rebuilder won't warranty the box unless you unweight the front wheels. Apparently that truck is too heavy and will damage the box with full weight on the box and no heelsassist.

For that reason, I always unweight the wheels regardless of what vehicle I'm working on. It's a case of better safe than sorry.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Glad it all came out okay .

I hope you removed the filter and cleaned all the old black sludge out of the lower reservoir .In any case do not be dismayed if the new ATF turns dark in 500 miles, just drain and refill it again .

Turning the steering of any vehicle with out moving the wheels or raising them off the ground is very bad practice .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

That's what I do. I suck the stuff out of the reservoir with a turkey basting or similar device, remove the filter and try to wipe the reservoir clean, then disconnect the return hose and aim it into a bucket or something to catch the stuff. Then I fill the reservoir with new fluid. With the front up or the wheels on pieces of plastic or, as someone noted cardboard will likely work as well, start the car with the steering all the way one way. Then I have my wife or son in the old days, turn the wheel slowly back and forth while I add fluid to the reservoir until the stuff coming out the line aimed into a container comes out clean. I let the level get a bit low in the reservoir and put the new filter in. Then I figure it is all new fluid in there and put the return hose back on the reservoir and run the engine again while topping the reservoir off, and close it up with a new gasket. Newer cars are a bit different but I think the process is pretty similar.

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)