Servotronic Steering Rack Service.

[Nj]

nuts to that mate. I'll wait until something tells me I have to do it before worrying about it.

[4WheelDrifter]

As I suspected 'N' and 'P' are sleaves for re-fitting the seal in the end of the rack.

Thanks to Pirvu Eugen for his reassurance on pulling the pinion out. It was as simple as holding the steering spindle in a vice and tapping the rack body away from it.

So here the steering rack is, completely dismantled showing the rack and pinion.



Now I just have to make sure it is completely clean and reassemble it.

[4WheelDrifter]

Here's the main pinion bearing. If you fancy changing that one it is made by SKF, P/N 61906 ETN9+.



If you want to change the small bearing at the tip of the pinion shaft you are on your own, I'm not digging that one out.

[s2driveruk]

excellent stuff, glad you have it out in pieces ok. Looking fwd to seeing what you reckon once the car is up and running again!

[Pirvu Eugen]

Hope that everithing will be OK!
All the best!
Eugen

[4WheelDrifter]

I reassembled the steering rack last night with no problems.

Here is the bare housing after I cleaned it up and gave it a coat of paint….



…and here it is back in one piece.



I realised in my previous posts I didn’t show where o-ring ‘K’ went. That goes under the preload adjustment bolt.




Now I just need to order a new boot and retainer for the end of the rack to complete the overhaul.
Part numbers for those are:
861 419 845 A - Hose clip.
811 419 831 B – Boot.
893 422 837 A - Retaining ring.

[4WheelDrifter]

Overall I found the job pretty easy once I knew what pulls out where and how. The bulk of the time seemed to be taken up by thoroughly cleaning all the parts and tools used before the reassembly.

Tools used:

6 mm allen key – for pinion housing.
10 and 13mm spanners – for preload adjuster.
17mm Hex key. – for rack end cap.
Suitable drifts * – for removing/replacing seals.
Mallet – for removing pinion.
Internal circlip pliers – for rack end seal.
T10 and T15 Torx bits. – for Servotronic controller.
A needle – for hooking out o-rings.

A vice is useful too, but not essential.
I also had a bottle of G002000 handy, to coat all the internal parts, seal and o-rings before refitting.

– * The back of a 24mm socket and an extension bar worked well. I also used a long brass bar for gently teasing out the rack end seal ‘M’.


The most nerve-wracking part was pushing the rack rod out through the end seal. You use the plastic fitting sleeves, parts N and P for that, but it still took a bit of a push to get the rack through.

Here are some more pictures in case it helps:

New end seal pushed in and circlip installed.


Fitting sleeve is then placed inside.


Part N is then dropped out the other end of the steering rack housing, leaving part P behind.


Steering rack rod is then carefully threaded through the fitting sleeve, then pushed through the seal.


The pinion spindle seal is pushed out from the top.


Then pushed back in through the bottom.


The rest is plain sailing really, just replacing all the o-rings.

[4WheelDrifter]

I also scanned these diagrams that may be useful in the future. They are for a Coupé quattro from chassis 8B MA002645 onwards, non Servotronic but the same idea.

[s2_bo]

I wish all guides on here were as detailed as this.

20/10 for the write up Stu!!

There's definitely no excuse for me not to do mine now...

[4WheelDrifter]

I wish all guides on here were as detailed as this.

20/10 for the write up Stu!!

There's definitely no excuse for me not to do mine now...

Cheers Bo. I was thinking I might have overdone it.
Yeah. Crack on with it Bo. There maybe some details I missed.

[Nuvo]

That's an excellent write up Stu with some really detailed pics to go with it. I be coming back to this when I get the chance to give my rack an overhaul.

Definitely a worthy contender for being made a sticky.

[s2driveruk]

Got to echo Bo and Nuvo's comments, this is exactly what we need on here. Had i seen all this whilst I was doing mine, I might have attempted to do it myself

Would be great to create basically an online Haynes style manual for the S2 made up of nicely detailed and photographed how to guides like this

Then there would be no excuse for the A2 guys to win the technical award next year

Well done Stu...looks as good as new.

[mcandmar]

Can somebody please explain how the servotronic part works? Does it regulate fluid pressure?

[4WheelDrifter]

Here are the final few parts I got to finish of the rack.



861 419 845 A - Hose clip.
811 419 831 B – Boot.
893 422 837 A - Retaining ring.




8A2 425 021 - Steering damper.

[RAOUL]

Excellent write up! Has anybody tried sourcing these parts recently? My rack is weeping (think i will be when i have to take it out!), so it could do with a overhaul i think.