What a feeling it will be! A properly adjusted W123 / W116 / W126 power steering box

[Stretch]

Here's what I did recently to try and regain that fresh out of the box feel for my W123 power steering.


The power steering pump had long been resealed and cleaned out (see W123 Vickers type 24 power steering pump questions) but as I was busy cleaning up the engine bay during an engine rebuild I thought I'd have a go at doing the steering box as well. I mean why not? I obviously didn't have enough to do...


I was influenced by this DIY (see http://www.davidpetryk.net/Mercedes/Steering.htm) that has been talked about quite a bit on Peach Parts. I like this DIY but I think the adjustments can be done a bit better.


When I looked at the FSM I found that the chapter is split into two PDF files on the CD. Reading through this chapter you could be mistaken for thinking that adjusting and resealing a W123 power steering box is really complicated – a bloody nightmare in fact – but I now think otherwise.


Performing ALL of the adjustments specified in the FSM does take time and you need to be patient but I think it is a straight forward DIY job with the exception of one bit => tightening the working piston. This does need a difficult to replicate special tool – but I've got a solution for that too; but it isn't a quick, easy or a really cheap one.

[Stretch]

Whilst I'll be covering most of the information in the chapters for resealing and adjusting the steering box in the FSM I encourage you to read through the chapters as well. Especially if:-

1. You have a W126 steering box
2. You are building one box from many others => Many parts are NOT interchangeable
3. You are replace parts (other than seals) within the box with new ones

There are subtle differences in these steering boxes, such as steering stops, no steering stops, self centring, no self centring etc. There is a whole chapter about this – chapter 46-010 and loads of information in chapter 46-220.


In the W123 FSM there are two chapters that are concerned with measuring the friction in the steering system. One is covered in the refurbishment of the steering box chapter 46-220 (which is the subject of this thread) and the other for measurement of the steering system fitted to the car with the wheels on the ground: This is chapter 46-120 which can be briefly summarised as wheels on ground, engine at idle => force required to turn steering on steering wheel nut should not exceed 5-7 Nm.


Please note chapter 46-120 is a check. It is only a check – not a method of adjustment. From comments on this forum I understand that adjusting the steering box play in accordance with the check procedure in 46-120 or just nipping up the adjustment screw is quite commonly done. Fair enough – but – before you do that please have a look at the final adjustment procedure at the end of this DIY... I have some extra information and a warning for you!


For the record my steering box has the following identification marks next to the “drain” bolt (which is actually a cover for a hole where a special tool pin is used to locate the centre of the steering):-

YY

This means that I have a second version steering box with an internal stop. It just so happens that it does not have the automatic compensation for play. The part number for the main casting is 116 461 04 01. This might seem like trivial information but it might help some of you out there.

[Stretch]

I'd like to be able to give a definitive list of the tools that you'll need. Unfortunately there are many different variants of this steering box depending on whether it was meant for the W123 or the W126 or whether it was an early or a late version.

• 65mm open ended spanner => for most W123 steering boxes ONLY – W126 is different and so are some of the earlier steering boxes!
• 6mm Allen key
• Special tool – to remove and tighten the nut on the working piston
• Pin spanner with 4mm pins
• Self made special tool to measure friction => Strong but light bits of wood, 2 wood screws, some wire and some 'heavy things'!
• Kitchen scales that measure in intervals of 1 gram
• Instead of the wood and kitchen scales listed above you could alternatively get a fancy torque wrench and expensive special tool attachments that fit on splined shafts... or any of the other special tools listed in the FSM...
• Circlip pliers
• A vice / method of holding the steering box (so that you don't damage it)
• A set of old fashioned hanging scales if you decided to tighten the steering nut

[Stretch]

I've set the names of the parts of the steering box in the following photographs.

[Stretch]

First drain the steering fluid. Turn the steering wheel all the way to the left...



...and undo the little screw on the steering box...



Catch the oil as it pours out.

Disconnect the supply and return hoses from the power steering pump.


Disconnect the centre steering stay ball joint from the Pitman arm.


Centre the steering wheel if you wish and then disconnect the rubber flex joint between the steering box and the steering wheel shaft.


Whilst supporting the steering box remove the four bolts that hold it onto the side of the engine bay. The heads for these bolts are in the wheel well. Warning:- the steering box is heavy and awkward – mine weighs 14kg.


If you struggle with these stages, stop and ask yourself if you really want to continue. Adjusting a steering box does get a bit harder than this! (Please note I've given you a bit more information than that presented in http://www.davidpetryk.net/Mercedes/Steering.htm, but I do agree with the “If you can’t figure how to get the gearbox off the car you don’t need to be taking it apart” comment)


Clean the outside of the steering box if necessary with your favourite engine degreaser.


Remove the Pitman arm.


For removal of the Pitman arm there is a special tool / puller for it – but chatting with the chief mechanic at the dealer he said that you usually have to resort to using heat (and lots of it). I tried with a Butane blow torch but it didn't work – shame of shame I got the mechanic to remove it for me. I don't think he bothered with the special tool.

[Stretch]

Not really rocket science this bit.

There is a control valve at the back of the steering box, where it attaches to the inside of the engine bay. The sealing cap on mine was pretty rusty. After removal of the circlip it took a lot of persuasion and penetrating oil to remove the sealing cap.



Inside you'll find two springs on either side of a shuttle valve. The FSM says you are NOT to dismantle this part any further. I didn't.



Next remove the bolts that hold the output shaft cap in place. This is the part from where the Pitman arm shaft / output shaft emerges.

Remove the little O ring on the back of this cap. Remove the large seal on the outer surface of the cap after removing the circlip.

Next remove the lock nut on the adjusting screw which is positioned at the other end of the shaft that holds the Pitman arm (see photo below). You will probably need to hold the screw thread still with a 6mm Allen key. Next screw this thread all the way into the steering box with the 6mm Allen key. The whole shaft will come out.

[bonebreaker]

i see is an old post!! do you remember if is a spring inside the control valve of the steering box?
thank you a lot!!

Originally Posted by Stretch

I've set the names of the parts of the steering box in the following photographs.

[AfricaXJ6]

HI There,

I tried to remove the control valve as first step. after I open the cover.

Cannot pull the control valve out. am I missing a step ?

I am assuming nothing else must be removed before the dontrol valve is taken out as per post #6

please guide me on removing the control valve-

thanks
c

[rs899]

Wow! I am impressed. Thanks for this. Too bad you are on the other side of the pond. You could probably do quite a business in rebuilding these from forum members.

[Stretch]

Originally Posted by rs899

Wow! I am impressed. Thanks for this. Too bad you are on the other side of the pond. You could probably do quite a business in rebuilding these from forum members.

Thanks - however, now that you know how to do it you can do the east coast, someone else could do the west and I'll stick with little old Europe.

[layback40]

The question is Army;
When will you have it all back together & road test?
Sorry if i sound like the grief you are probably getting at home !!

[Stretch]

Originally Posted by layback40

The question is Army;
When will you have it all back together & road test?
Sorry if i sound like the grief you are probably getting at home !!

Yeah good one...

I'm half way through my paint job. I'm stuck painting outside which is less than ideal in a summer with more rain than we had in the winter. I'm getting to the stage where I'll be off to the technical college just round the corner to see if I can hire a spray booth.

As for the transmission - that's back together so in principle I could fit that and the engine and get it running. Virtually everything else has been done.

I have a bit of rust to repair on the floor pan - that's what I'm doing today between the showers from the heavens. And whilst I've got the interior out I guess I should check the condition of the heater matrix...

...you see even for an idiot like myself who insists on taking everything to bits a car is eventually a finite thing. There won't be anything else left to "fix" soon.

[rs899]

a car is eventually a finite thing. There won't be anything else left to "fix" soon.

You know that's not true, especially if , like me, you move at a glacial pace.

When the first thing you did was years ago, its time to re-fix it.

[boneheaddoctor]

Fantastic writeup. Thanks.

[dieseldan44]

Amazing writeup Army. Thanks for walking us through this.

I dont know if I'll have time to do such a task, but its interesting to see how it's done.

I am dying to know how it works compared to before! I have no idea what a 'new' steering box felt like. Supposedly they did have a center 'dead' spot even when new.