Magnvs

I've got an '07 S8 that had a coolant hose rupture. After having that fixed at the dealership, a power steering hose ruptured a week later. My mom has an '06 A8 that had the same issue with the coolant hose rupturing and now that it's been repaired, the power steering system appears to be losing fluid. It's not spilling onto the ground, but appears to be leaking within the system. We fill up the reservoir, but it's low again after a day or two. A tire fixing place told her that it was a bad O-ring in the system. Is it possible to fix this as a DIY? Any known issue between these two repairs, or is it just a coincidence. They were repaired at different dealerships.

MP4.2+6.0

If losing fluid, inspect carefully for leaks. Honestly, your BEST answer is you do find one and then fix it. The problem sometimes is fluid is in fact leaking out somewhere, but with the belly pan underneath it is landing on that pan and not yet finding its way to ground, or blowing off the cover and splashing onto the underbody as an oily mist when the air at speed blows it further back. I've seen both on Audis over many years. To evaluate carefully, if not obvious from above the belly pan should be removed to look for signs of the PS hydraulic oil spilled onto it, and/or any leaks visible from below.

The worse answer is the o ring comment. That is most likely shorthand code for a bad o ring in the steering rack, also known as a "blown rack." If you open the boots where the inner tie rods are (very hard to get a new clamp on, so may just want to leave it be if leaking is relatively minor) and find oil in there, it's blown. Requires a new or rebuilt rack, which costs $ but is also a pretty painful and expensive labor job. In this case of rack related leaks if minor leaking, like a small part of a can of fluid over a year, likely just live with it. If it is the can a week or a month type thing, it will make a huge mess fluid wise, that tie rod boot will eventually not be able to contain it, and it will get expensive as the cans add up. Really no choice then but to replace rack. BTDT too, on my dad's 5000T he bought used with a leaking rack.

Mister Bally

I swear on the old (C4?) Audi 5000's that when the car began to be built on the assembly line, a pair of forks stick up out of the chain drive in the floor of the Neckarsulm plant and the first thing placed on it was the steering rack. Then the rest of the car gets attached to the rack and the car is built around the steering rack.

What a royal pain in the *** to replace.

Yes, once I was up to a Liter can every two weeks, I replaced the rack.

03_AR_CO

I replaced the rack on my '84 5000 as well, honestly not all difficult. I don't think I am up to the task of replacing one on a D3. As for the PSF leak, or introduction of air. Check as many of the hoses that you can. My 04 had similar symptoms and I ended up finding two minor leaks. One was a loose clamp on the return side of the power steering pump, things got better but not entirely after I replaced that. Found an additional loose clamp behind the drivers side fog lamp cover, where the power steering lines pass into the radiator or cooler. Keep us posted on your findings.

Mister Bally

Mine was an '87. Turbo engine and Quattro. No room to work to disconnect hydraulic lines, tie rods or to get the rack unbolted and out through the side. For me anyway. No hoist, jackstands and ramps were what I have to work with.
On a different subject, since quattros back then were only available with sticks, when I had to replace the clutch, removing the transmission was another pita that required two floor jacks to remove the trans. once the three driveshafts and exhaust was removed.