[urq] Red or Green? (revisited)

[SpotatAshleys]

Well the job is done and all seems fine. The reconditioned rack is in and the system converted to the green mineral based fluid. Many thanks to all who replied. I checked out all the various forums available to quattro sufferers and it's amazing the variety of opinions just on this subject. This of course left me still not sure.  
Anyway, I checked out the SJMAutotechnik website but this didn't quite answer the question. Next I emailed SJM and Scott kindly replied as follows:

"I have spoken with the folks at ZF in the USA regarding their rebuilt steering racks for the Audis and which fluid should be used. They said the seals are compatible with most automotive oil, engine oil, red ATF, pentosin etc, but that most manufacturers specify thier own particular oil so the steering will work well under the specified range of ambient air temperatures. The reality is you could run either red ATF of the Pentosin, but I would remove, and/or flush out the existing ATF if you plan to switch over to Pentosin"

Many thanks to Scott for this.

So that's what I did. To flush it out I disconnected the three returns to the reservoir from the rack, bomb and servo blocked up the reservoir intakes. The return pipes were extended with other pipes just slipped over them so that they reached a bowl on the ground below the engine. Then adding green fluid to the reservoir and running the engine for a few seconds at a time I kept checking until green fluid came out in to the bowl. Working the rack from side to side purged and bled the rack. By depressurising the bomb after each run of the engine the servo eventually expelled the red fluid. All done with the minimum of spillage. I bought 4 litres of the green fluid (at £9.00 per litre!) and used 1.5 in the flushing, about another 1.5 in filling and just a bit from the last one to top up.

The steering feels great and suggests to me now that the rack was really badly worn before.

One final point: The rack I had reconditioned was the actual rack off the car (as far as I know this was the rack it left Ingolstadt with in 1986/87 - at least none of the paperwork I hold suggests it was ever changed) The Audi part number is: 857 422 065A and the ZF Part number 7881 955 122. The Coupe quattro (1985/86) rack I had in briefly was 812 422 065C and the ZF number 7881 955 119. There is no difference between these racks as far as I can see. They are the same in all respects (dimentions, ratio etc) except for the pipes feeding and returning the fluid and these simply un-bolt. Both racks run on the same kind of pump and the same pressure rating (75 bar).

So there we are.
Many thanks to all of you once again. I hope this helps as far as the Red or Green debate goes. If I do encounter any problems though, be sure I will post them here but the smart money says all should be fine now..

All the best

Keith 

'87 WR (Those of you Stateside, don't forget that the part numbers above relate to RHD but I guess the same will apply to LHD urqs and LHD Coupes/Coupe quattros)