Help wanted on refurbishing power steering box

[rutger kohler]

I am retro fitting a power steering unit off a W108.  i have been given all the repair parts kit with the unit and am now replacing parts with the kit.  One of the large teflon rings fits on the end of the power piston. I am not going to disassemble the end of the power piston as all the parts are ok and it require two or three specialist tools.

The supplementry manual I have suggests heating the teflon ring up to 80C before fitting and i imagine this means the teflon ring will expand sufficiently to slip over the end of the assembled power piston without disassembling it.

is this correct plse?

[tel76]

Yes, you heat up the Teflon ring in hot oil to the temperature you stated, the Teflon ring will then smoothly pass over the piston, the ring when fitted over the piston will seem to be very slack, when I did mine and before the Teflon ring had cooled I temporarily fitted the piston back into its housing, this allowed the ring to regain its natural size, after it had cooled I removed the piston and continued with the rebuild.
On the first box I overhauled I completely stripped the piston, on inspection of the parts I found no wear on any item, as a result of these findings each subsequent box I have overhauled I have not stripped the piston.
Eric

[rutger kohler]

Hi Eric, thanks for that, will continue with rebuild. This is what makes this club so great.

thanks again

Rutger K

[rutger kohler]

Eric, just wondering how you put the ball bearings back in. Again the supplementary manual is vague about this. I see the repair kit has a new lock tab for the little cage that redirects the ball bearings and I wondered if there was an advantaga in taking this off and feeding the ball bearings back in through it, after fitting the worm shaft back in?

[tel76]

Remove the cage, push the worm into the piston and feed the balls into the orifice, keep moving the worm until you have as many balls installed as you can get in (put them in dry, they slide in easier), you then put the remainder into the cage using grease to hold them in position, make sure you get the full amount into the worm/cage, I cannot remember if it is 30 or 31 that is required, you will find the answer if you check out using the search facility.

[rutger kohler]

Hi Thanks for that, have to ask the wife for an old pot to heat the teflon ring up, in oil.  I guess you use the power steering oil, is this ATF?

cheers

Ruitger Kohler

[tel76]

I did not ask the wife but I did borrow one of her shallow pans, I did clean it before I put it back on the shelf,  what the eye does not see the heart does not grieve.
As heat source I used a plumbers butane blow lamp and the oil I used was engine oil.
As a matter of interest when you have fitted the Teflon ring onto the piston you will be very disappointed with the fit, you will find it will seem to be very slack, as I indicated in my post above temporarily push the piston into the bore and let it cool before removing to continuing with the rebuild, you may find that you have to re- warm  the piston/Teflon ring to get the piston to easily slide into the bore.

[Dave H]

Make sure you get all the balls back in.
It's a bit of a fiddley job. If the balls don't
Run smooth down the hole clean all parts
And start again.
Fit the remaining balls into the cage.again this
Is fiddley work and retain them with a blob of
Grease. Don't expect to get it right first time
But you will get the hang of it after the 5 th go.
Just make sure you refit all of the balls you took out.

[Dave H]

Also to set the turning torque 1.4 to 1.6 ft/lb on the shaft this is a
Very low setting. A very accurate way to do this is to hang  1.5lb
At a foot length on a weightless balanced shaft. This is how torque
Wrenches are calibrated so you know it will be accurate.
I used 1.5 pints of water as a pint is roughly a pound.
It looks a bit Heath Robertson but its how Issac Newton would of done it.
Check out the tech manual for more info on setting the box up.

[Dave H]

Couple more pics..

[rutger kohler]

Just a quick note back to say thanks for all the help so far, amazingly the 31 balls went straight in, thanks to your tips.  I have made a newtonian balance as per provided photos but still have to put the power piston back into the main housing before i use it. Fitted the PFTE power piston ring, it might be worth noting that the PFTE ring does not instantly expand at 80C, it took 10 minutes and several attempts for me.

[Dave H]

Well done getting the balls in first time... I had a nightmare with mine !
Also the Teflon ( ptfe) ring can be heated in water  to 80 degrees.
It doesn't have to be oil.
It's only to make it a bit more pliable so it stretches over the piston.
Ptfe is unique in that it has" plastic memory" and returns to its original shape.

[George Des]

You can also coax that ring to shrink back in properly by getting a large metal band clamp and tightenin it around the ring and ten letting i sit fora few hours.  Just be sure you somehow protect the ring so the metal band does not nick the ring.

[rutger kohler]

Hi, have got my power steering box back together and am starting to set the torque. Referring to the hand sketches and notes in the technical forum  by Dave H, in the first step an astericked note say "back off tension on adjustment screw before setting the front bearing torque"  Does this refer to the threaded rod with the 7mm A/F rod?

cheers

Rutger K

[Dave H]

Yes .. Turn the threaded rod clockwise a bit to remove any tension within
The box.
In step 1 all you are doing is setting the turning torque of the front bearing.
Hope this helps.

[rutger kohler]

Hi Dave, thanks for that, have done so.  The end of the threaded rod on my unit is mangled.  I understand that the end of the shaft is 7mm.  Is this just two flats or was it originally a hexagon plse? 

[Dave H]

2 flats... Picture might look a bit hex but its definately 2 flats.

[rutger kohler]

Hi Guys, have finally finished my overhaul on the power steering box but have found the output shaft torque is a bit too tight after checking with the measurements by Dave H.  Does this mean I should ease back on the big round nut more?

[Dave H]

Have you had the torque wrench on it? What did it move at ?
I thought mine was never going to move also.
This was until I secured the box firmly in a vice and it turned at about 22 ft/lb when centered.
The steering is supposed to free up a bit either side of central .
Got mine too about 16 ft/lb at near extreme right and left.
The big round (2 inch across nut) is only locked in place against the hex nut.
When you do this you should not alter, draw out or move the tension on the adjusting screw in any way.
By tightening the round nut against the hex nut you are making a lock nut to hold the position of the adjusting screw.
If you don't get near these figures back off the adjusting screw a touch and lock it again and then put the domed cover nut back on
Which protects the threads.
Hope this helps .
Dave

[alchemist]

There was a nice detailed article with pictures in the STAR Magazine several issues back (possibly 4-8 issues) explaining the building of steering boxes. I thought this helps.

[rutger kohler]

Guys, thanks for that. I got more than 26 ft-pounds however on reflection when I reassembled the box I didn't oil anything except put grease in between the two seals on both shafts as recommended.  Will drop a bit of ATF into the centre screw hole and work back and forth and reset the big round nut, however won't be for several days.

cheers

Rutger K

[Harry]

I am rebuilding my PS Box and had some questions for the forum, please.  This is a 1966 230SL, and the box has been leaking so I removed the assembly, removed the pitman arm and steering coupling, then began disassembling the unit itself.  I had looked across the forum and tech manual for guidance as I began the task, and printed off some relevant posts/articles.  I realized this evening that all of those pertained to manual steering.  I have removed the cover at the pitman arm, removed the shaft that it attaches to and began to remove the assembly that the steering shaft attaches to.  It appears that this assembly cannot be removed until the "valve assembly" is removed first because the outer diameter of the assembly won't clear the valve assembly.  So I removed the bolts securing the cap where the inlet and outlet lines connect but the cap still seems to be pretty tightly seated.  (See photo.)

I can see there is a gasket between this cap and the body of the box so it is clear it is removable but I am hesitant to pry it off until I checked with the forum.  I certainly don't want to muscle something that might still be attached in some manner.  At the opposite end of the body, there is a seat that a spring its over (see that photo as well) but it doesn't have any visible means to grasp or loosen (to remove the valve assembly from that end).

I would very much appreciate some advice from others who have performed this task.  Also, if there is a kit that I should get, that would be helpful as well.  (I have a kit that I ordered but I think it may be for manual steering.)

Thanks very much,
Harry

[Harry]

Rutger - I am rebuilding my 1966 230SL PS Box.  I am having mild difficulties getting the unit disassembled.  It appears that you have to remove the "valve assembly" before the main unit (that attaches to the steering column) can be removed.  There seems to be interference otherwise.  Can you offer some guidance?  Any photos would also be a great help. And - any in-progress photos would be super.  (I just posted some photos under this section.)

Thanks,
Harry

[rutger kohler]

Hi Harry, the power steering unit that I overhauled is off a W108  so although it will work on my 280SL it is not the same unit as a stock 230SL unit. There is a very good step by step post http://www.davidpetryk.net/Mercedes/Steering.htm which may well suit yours as it is not for the W108.

good luck

[Harry]

Thanks Rutger.  I have printed the Petry post and referred to it extensively.  Unfortunately, it pertains to a manual box and falls just short of the information that I need for the power unit.  I did find another post last evening that I will use to also help.  It is for a power unit and although it doesn't provide instructions, it does provide all of the parts for this type of unit laid out on a table.