W123 (300D) steering box - question about steering nut and working piston
 

G'day All,

I'm busy playing with my steering box at the moment and I've reached a bit of a problem.

The steering box is in bits and I'm looking through the FSM (chapter 46-220) particularly the bit about the working piston and the steering nut.

The steering nut is the bit that sticks out the side of this tubular bit (the working piston) that houses the 24 (count 'em!) recirculating balls.

http://www.peachparts.com/shopforum/...1&d=1304968932

Now - here's the problem - the FSM (page 29) states that the steering nut should move with a friction torque of 6 to 10 Ncm (that's Newton CENTIMETERS not meters)...

...mine just flops about flaccidly...


Has anyone ever taken a box to bits this far before and found a stiff one?

Oh yeah - to adjust it you need to tighten the lock nut and cover to 200 to 240Nm - eeek - that could make your eyes water!

Sorry for being childish...

But is there a potential problem here with these steering boxes if this comes too loose?

The steering nut will eventually go loose as there are some ball bearings (unknown quantity at the moment) at the opposite end of the unit from the two nuts on the front.

To tighten these nuts you are meant to use a special tool that allows you to hold the smaller nut (clearly visible in the picture above) whilst tightening the lock nut (a larger ring not that clearly in view) to 200 - 220 Nm. So there is a sort of hollow big socket that has space for a drive to hold the inner nut on the cap.

Links to the special tools:-

http://www.startekinfo.de/etools/content/tool.jsp?toolno=123%20589%2008%2009%2000

And

http://www.startekinfo.de/etools/content/tool.jsp?toolno=126%20589%2000%2016%2000

Oh dear =>

"here I go again on my own,
going down the only road I've ever know,
like drifter I was born to walk alone"

I resealed mine, but didn't fully disassemble so I can relate to the "how can I can make it like new" desire.

But some wear and slop is inevitable and you might be going too far with the 6 Ncm friction setting. What are you going to do when the worm gear and the piston don't meet the tolerance? I checked the FSM and it says they're matched at the factory for the best fit.

Maybe try tightening that if the tools aren't too pricey, but it may be a wild goose chase. I'd consider putting new bearings in (either 6 mm or 7 mm, if I recall) and that may tighten the steering a bit - quality steel, of course.

How's the wear on the Pitman shaft?

Hi Yak - I'm not alone - thanks!

The Pitmam shaft is fine - in fact everything seems fine - except for this floppynees...

I was just thinking that it might be one of those bits that gets installed correctly and then within 30 seconds of use it is out of limits as a result of the design. So I was kind of thinking that it might be a "don't worry about that" thing it isn't worth the hassle...

...but then again I see the challenge!

Update
 

The 60mm - 8 sided - lock nut on this part needs a socket that fits in a range of other special attachments... the socket alone costs nearly 170 euros

http://nl.mbspecialist.com/mercedes_webcatalog/item/123589080900/

Be warned however this is only good for 123 steering boxes there's another one for the 126 which has a 65mm 8 sided socket...

...I might not bother taking this bit to pieces...

Audaces fortuna juvat

-or maybe -

Discretion is the better part of valor.

Your choice, but I'd leave it alone.

Progress
 

Sorry Yak - I do respect your advice but it turns out I'm more inquisitive than I thought.

I've been messing about trying to make a socket to fit this big nut but I really really can't weld for toffee so this attempt failed. May be this idea is good for someone who can weld? Probably not though I can't see it holding 220Nm - the plan was to use a big spanner on the outer sides of the bent bit of metal...

http://www.peachparts.com/shopforum/...1&d=1308663278

So plan B has been to visit the CNC boys and get a new socket made.

This has almost worked out well. There was a bit of a problem with first and third angle projection and the meaning of dotted lines. Here's a picture of the bit I asked them to make. Unfortunately they ended up making something with two male ends instead of a female 8 sided socket with a male 6 sided end.

If anyone wants to use this drawing please feel free to do so at your own risk - I'm not a professional draughtsman and there was some confusion when I showed it to the (Dutch) CNC chaps here.

http://www.peachparts.com/shopforum/...1&d=1308663706
I'll post a picture of the modified part when the CNC chaps finish their work on it. It will end up being a bit shorter than the 60mm one I designed - it will probably be closer to 40mm and not as meaty - I hope it will be good enough for 200Nm. We'll have to wait and see.

(Happy days!)

I don't suppose the geometry on a 60 mm bi-hex would work? They're only 15 pounds.

Nope it doesn't fit the points on the 8 sided nut and there isn't all that much space in the recess to fit a big socket. It would probably have to be a thin walled big socket if anyone makes them...

Here it is - works a treat!
 

As I said in earlier posts there was a bit of confusion with the machine shop and they planned to modify the bit that had been made to suit my requirements... that didn't work out so they made a new one.

Here it is:-

http://www.peachparts.com/shopforum/...1&d=1310833734

http://www.peachparts.com/shopforum/...1&d=1310833773

It works a treat - the working piston is in bits.

Time to adjust my steering box to see if I can get that as new feel I'm looking for...

I thought you only had too much time on your hands in the winter...
We blamed it on ' cabin fever'... but now I am beginning to worry.... about your safety....

By safety do you mean sanity?

Speaking of sanity - I just got a price for a replacement working piston (it comes complete with the axle that goes down to the Pitman arm). Guess how much?







555.21 euros excluding taxes - still available though!


Boy am I glad I didn't break it.