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  #1  
Old 10-27-2018, 06:00 PM
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URGENT help needed! Steering box gone wrong

I bought a remanufactured steering box because the original in my '81 300SD was leaking. Installed today and now it doesn't want to turn to the left! Turning right is just as smooth as the old box, but turning left requires WAY more effort. Only happens with the wheels on the ground - in the air is easy either direction, engine on or off. Drove it around the parking lot thinking system just needed to be bled, but after 10 minutes of driving around turning the wheel back and forth, no change. Tried adjusting the box by turning the allen bolt on the top clockwise, no change.

Looking under the car, nothing appears to be binding. Steering was great with the old box, just was leaking like a sieve. Did I get a bad one?

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  #2  
Old 10-27-2018, 09:35 PM
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I don't think this is the issue but there is a Bolt at the bottom of the Steering Box close to shaft where the steering arm attaches. It will have an aluminum or copper cursh washer.

With the Wheels Pointed forward (engine off) when you remove the Bolt/plug (some Oil will drip out) look past the threaded area and you should be able to see a hole. That hole is where a special taperd check bolt goes to center the Steering Box. However, you are just looking to see if you can see it.

If you cannot see it then have someone turn the steering wheel slowly (enging off) until that inside hole lines up with the threaded bolt hole. When it does look at the wheels. If the wells are not straight forward that means the arm is mounted in the wrong position (I don't know if that is possible).
Keep the Stering box with that hole lined up with the threaded hole and pull of the Arm and straighten the front wheels and re-install the arm so that the wheels are straight. Then everthing should be centered.

Note that when everthing is centered you steering wheel also should be centered.

Member Marturo has that he rebuilds steering boxes. You could also ask him for info.
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  #3  
Old 10-27-2018, 11:49 PM
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I understand that the purpose of the hole is to get the steering centered. There is a rod tool one can insert to lock the box there (not req.). Then when you adjust the steering links on L & R (per an alignment machine) you should wind up w/ the wheel centered when driving down the road. I have never done that. I just try to get the links showing the same # threads on each side, at proper toe-in. Then, drive a bit and if the steering wheel is not centered, adjust accordingly. I generally have to tweak the toe-in after driving anyway as things settle so usually no extra work to get the wheel straight. Anyway, the only way this would affect your issue is because the box is tighter at the center, so if that point shifted to the left you might feel more binding as it sweeps thru the actual box center there. Would also mean you have the sector shaft adjustment too tight (bolt w/ locknut on top).

I expect the Pitman arm splines are keyed, as they are on my Chrysler boxes. If so, it only goes on one way so don't try to clock it per post #2. The other thing that could translate from Chrysler boxes (don't know GM & Ford) is that those have a spool valve adjustment. You loosen 2 bolts and tap the valve housing back & forth until centered so the front wheels don't self-steer (engine running, wheels off ground). I expect M-B uses a similar spool valve which has an adjustment but never been there with my 300D's.
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  #4  
Old 10-28-2018, 09:37 AM
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Count the number of turns lock to lock and find out whether you are getting full range of motion out of the box.
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  #5  
Old 10-28-2018, 10:06 AM
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Thanks for the replies.

The box is centered and the steering wheel straight, so no problem there. I tried driving some more, thinking it could just be a stubborn air pocket in the box, but it's still the same. Feels fine turning to the right, but turning to the left (even to get back to center after turning to the right) feels like there's no power assist at all. I even checked the feel with the engine off and on and they feel the same turning left.
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  #6  
Old 10-28-2018, 11:31 AM
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While I know it will be a PITA, can you put the old box back in to confirm it works fine with the old one and bad with the new? That would also rule out asssembling it wrong causing the issue. Just my .02
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  #7  
Old 10-28-2018, 03:52 PM
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Quote:
Originally Posted by psaboic View Post
While I know it will be a PITA, can you put the old box back in to confirm it works fine with the old one and bad with the new? That would also rule out asssembling it wrong causing the issue. Just my .02
When the front wheels are off the ground, the steering is super smooth in both directions, engine on or off. If something was binding up, I think I'd notice it under these conditions.
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  #8  
Old 10-28-2018, 05:19 PM
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You say "with the wheels on the ground", are you lifting the car using the cross member?

Try supporting the car with jack stands under the control arms. This will more closely simulate the actual conditions. It might assist you in locating a "bind" if there is one.

Have you done anything else to the steering? Tie rod ends, idler bushings, etc.?
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  #9  
Old 10-28-2018, 06:03 PM
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Disconnect the pitman arm and determine whether everything from the steering wheel through the box moves freely. Do this with and without the engine running. Next, disconnect the steering knuckles at the tie rod and make sure they turn freely.
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  #10  
Old 10-28-2018, 09:24 PM
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Quote:
Originally Posted by Mike D View Post
You say "with the wheels on the ground", are you lifting the car using the cross member?

Try supporting the car with jack stands under the control arms. This will more closely simulate the actual conditions. It might assist you in locating a "bind" if there is one.

Have you done anything else to the steering? Tie rod ends, idler bushings, etc.?
Good tip on the stands under the control arms. I'll try that.

Nothing at all was done to the steering except disconnecting the tie rod and drag link from the pitman arm. All are in good shape and the steering was great with my old leaky box.
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  #11  
Old 10-28-2018, 10:09 PM
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I'll own up. This is a box I rebuilt and sold to him.

Nothing was wrong with the box, not considerably worn and pretty clean on the inside when I first broke it down. I'm digging into my manuals tonight before bed a bit further, but I'm at a loss. I've never heard of this problem before, nor have I experienced it.
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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]
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  #12  
Old 10-29-2018, 09:15 AM
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Found this today

http://www.peachparts.com/shopforum/vintage-mercedes-forum/341386-w123-power-steering-only-one-direction.html
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  #13  
Old 10-29-2018, 11:43 AM
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Quote:
Originally Posted by martureo View Post
I'll own up. This is a box I rebuilt and sold to him.

Nothing was wrong with the box, not considerably worn and pretty clean on the inside when I first broke it down. I'm digging into my manuals tonight before bed a bit further, but I'm at a loss. I've never heard of this problem before, nor have I experienced it.


Spool valve or whatever Mercedes calls it is probably the issue. Directs flow of the hydralic fluid. To power assist the steering in the desired direction..
I never remember myself or any friend having a failure of one on any car. Yet if man makes it can fail.
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Old 10-29-2018, 11:03 PM
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Reading Stretch's write-up (again, forgot about it) that was linked above (http://www.peachparts.com/shopforum/diesel-discussion/303379-what-feeling-will-properly-adjusted-w123-w116-w126-power-steering-box-2.html), M-B calls the spool valve a "control valve". The FSM says to not open it and mentions no adjustments. It appears there are 2 springs to center it in the bore at a neutral position where the box won't want to self-steer either direction. I expect that those 2 springs are the adjustment and were probably hand-selected at the factory. Perhaps they were swapped during the rebuild (possible?) or springs from another box used.

Besides getting different springs, you might be able to shim one side or the other with washers, similar to what we do in the injectors. Problem is that would take much trial and error, losing a lot of fluid and even worse you must remove the p.s. gear from the inner frame each time to get at the port. Maybe only once. I would have the box in the air (Pitman arm off) w/ hoses connected and idle the engine to get hydraulic pressure. After a few passes, you could probably get the right shims. M-B probably had a hydraulic test bench and measured the off-center force so they could pick the right springs on one pass. You can find the Chrysler FSM (1960-70's) online to see how those gear-boxes adjust the spool valve (in-car, easy to get to on top), and perhaps other manufacturers are similar. martureo might even do enough refurb's to make rigging up a tuning bench practical.
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  #15  
Old 10-30-2018, 11:41 AM
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Quote:
Originally Posted by BillGrissom View Post
Reading Stretch's write-up (again, forgot about it) that was linked above (http://www.peachparts.com/shopforum/diesel-discussion/303379-what-feeling-will-properly-adjusted-w123-w116-w126-power-steering-box-2.html), M-B calls the spool valve a "control valve". The FSM says to not open it and mentions no adjustments. It appears there are 2 springs to center it in the bore at a neutral position where the box won't want to self-steer either direction. I expect that those 2 springs are the adjustment and were probably hand-selected at the factory. Perhaps they were swapped during the rebuild (possible?) or springs from another box used.
I never mix springs or disassemble the valve further. I clean the springs and then put them back where they belong. I've heard that others have seen broken springs, but I've only encountered two boxes in which the springs were so compressed they didn't look like they would be effective. I did not rebuild/resell those boxes and used them for parts.


I've reconditioned over 100 boxes at this point, so there's the reference for frequency of problems.
Quote:
Besides getting different springs, you might be able to shim one side or the other with washers, similar to what we do in the injectors. Problem is that would take much trial and error, losing a lot of fluid and even worse you must remove the p.s. gear from the inner frame each time to get at the port. Maybe only once. I would have the box in the air (Pitman arm off) w/ hoses connected and idle the engine to get hydraulic pressure. After a few passes, you could probably get the right shims. M-B probably had a hydraulic test bench and measured the off-center force so they could pick the right springs on one pass. You can find the Chrysler FSM (1960-70's) online to see how those gear-boxes adjust the spool valve (in-car, easy to get to on top), and perhaps other manufacturers are similar. martureo might even do enough refurb's to make rigging up a tuning bench practical.
I haven't encountered this issue until this box, so a test rig was just money wasted. I think I might just get a measurement on the next few boxes I do to see what the difference in springs are. I know Chris at C&M has been putting new springs in each box, and this might be something I'll explore in the future.

Keep in mind that the valve is in the guts of the box and requires you disassemble at least 75% of the box to get to it. That's a bit of time and energy just to swap out some springs. I can do a box in 3 hours if it isn't giving me any trouble, including cleaning and adjusting it. But that's ideal conditions, no interrruptions, no stuck bolts, no wear issues, the box has been maintained and I'm working quickly. A recently rebuilt box is quicker, as is a box that I'm just swapping things in and out, but even doing these regularly its a pain in the a55 to do.

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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]
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