Ghost Rider 549.

Just installed a "remanufactured" OE steering rack. After bleeding the system, and using Pentosin fliud, both main seals failed as the car was backed out of the garage.
Needless to say, my mechanic was really pissed after all that work to R&R the steering rack.
I'm would like to ask if anyone can advise me as to what (besides poor workmanship) might cause an infantile failure on the 2001 Allroad steering rack? It was as though the system suffered a major overpressure that blew the seals in the reman rack. However, I am not aware of anything in the steering system design that could cause such a major overpressure within the rack. The PS pump should not be capable of developing that much pressure. The advice I received concerning PS fluids indicated I could use the Pentosin fluid in this system with no problems. Therefore, before I replace the rack again, I'd like to track down the issue(s) and correct them first.
Thanks in advance for any help with this problem.

03gti18t

bump.
need this info

Ghost Rider 549.

?

silverd2

The power steering pump produces WAY MORE pressure than the steering gear needs, but if all is well with the pump, it bleeds off most of what it produces through it's internal relief valve.

The pump's minimum test pressure (all hoses blocked) at idle is 120 bar...that's 1740 psi at idle !! ...higher as rpms increase, regulated only by that relief valve.

Relief valves on most cars fail in the other direction...they stay open, killing boost to the steering gear.

I can't find a reference to how much pressure is used by your steering gear and don't have a solution to your problem. But I wouldn't completely rule out the pump's ability to blow seals, if completely unregulated...no personal knowledge though...just theory.

Ghost Rider 549.

Thanks for the response.
So, it is possible for the pump to blow out the seals if it's relief valve is stuck closed. I imagine this is most likely what occurred in my case.
I think it will be best to simply replace the pump along with the reman rack, just to be safe. These parts are not cheap, and the manhours needed to complete the R&R work, and the level of disassembly involved, dictate replacing both units, to ensure there is no repeat of the overpressure situation.
It will probably also be a good idea to thoroughly inspect the high pressure line(s) and banjo fittings before reusing them.
Thanks again for your input. I know hydraulic systems generically but, I'm not that familiar with the Audi PS systems, so I wasn't aware of the pressure relief valve issue in these pumps. You've helped me a lot.

silverd2

I don't know if Audi's in particular have "issues" with the ps pump valves...just that all (most?) modern mechanical ps pumps have these internal valves, including our cars. The pressure relief, when working, just reroutes the excess fluid/pressure back around to the intake side of the pump internally...not serviceable, from what I've read.

Also worth considering (just speculation, though...no experience): The banjo bolt fitting on the pressure line (coiled pipe) connected to the steering gear contains a non-return check valve.
The banjo bolt fitting on the return hose connected to the steering gear does not...it's just a regular open banjo fitting. Without looking, I don't know if these 2 are the same size and/or could be switched by mistake. They "look" the same in Bentley & ETKA drawings.

Old_School_Audi

Those banjo bolts are different sizes. Manufactoring lines do this as a quality measure to prevent incorrect assembly. FWIW: this is called "Poka-Yoke"

Ghost Rider 549.

This is just a follow up to my original post to report on what was found and how the repair has effected my 2001 Allroad.
The PS pump does appear to have been the problem. It was replaced along with the 2nd reman rack. All went well and, after a 4 wheel alignment, the car was back on the road.
The Allroad runs better than ever. In addition, the steering is much lighter and more positive. The most interesting improvement is that I have picked up about 3 MPG (21.5 MPG) on average, according to the trip computer. The old pump and rack must have been putting one hell of a drag on the engine for quite some time, cause the car had averaged 18.4 MPG from the day we brought it home (two years). Anyway, I'm totally satisfied with the repair and the resulting improvement in performance and mileage.
If you encounter Allroad steering problems, it may be advisable to replace both the PS pump and the rack. The reman PS pump was not expensive and, if you have everything apart anyway, put in a new one. Believe me when I tell you, you DO NOT want to do this job twice.

Old_School_Audi

I appreciate hearing the results from your repair. I was wondering just how they determined that the pump was mal-functioning. Did they test the output pressure on the old pump before replacing it?

Ghost Rider 549.

Basically we decided it was the pump when it immediately blew the seals on the newly installed remanufactured rack assembly. No, we did not test the output pressure.
The system really only contains the pump, the rack, the fluid tank, and the lines. The only component capable of producing an over pressure in the system is the pump. Once I was informed that the pressure relief valve is located in the pump, and that they can stick closed, it was fairly obvious that the pump had to be the problem. We did blow out the lines, inspect the check valve, and flush the system, before installing the new components.
All in all a costly lesson, based on replacing the rack twice and the pump once. Although, the reman OE rack was only a little over $200, and the reman OE pump was just over $100.
I reported the results here so others could learn from my experiences.