(Power)steering failure - turns out it's Crank Pulley failure.
 

Apologies...it's a little long.
On my way home tonight, I was doing a right-hand turn to merge out onto a dual carriageway, and as I turned to join the initial merging lane, I turned the steering wheel and the next thing the wheel wasn't turning and the car was going to go straight out into the traffic. I braked hard and luckily there was nobody behind me. My power steering was gone completely so with literally all my strength, I managed to turn the steering wheel to straighten the car up and roll it along the merging lane a bit towards the hard shoulder with my hazards on. I killed the ignition and started again but it was still the same. I wasn't far from home but as I started driving down the road all the windows suddenly fogged up as if something was going on with my AC.. On the way, any 90 degree corner I had to take I had to take it really wide, and even still would end up the far side of the road as I came around. Thankfully I got it home in the end and when I turned it off and got out, all the fans under the bonnet were going like billio. I went into the house and came back out 5 minutes later to do a scan. The battery had gone right down with 1 bar on the MMI screen gauge so I thought maybe the fans had depleted the battery. Anyhow, are fans any clue as to what's going on with my steering? When I was doing the scan I inadvertently started the engine, but when I saw it was charging the battery I decided to leave it run. Then I noticed there was a loud whirring sound coming from under the bonnet and when I lifted it, it sounded like a fan was rubbing off something, but as I shone my light in I could see the belt going around and everything looked OK except for the noise. Could it be a seized pulley or something? I'll try and have a better look tomorrow in daylight. Any ideas?

If you have lost all the power steering fluid, you don't want to run the pump without fluid. That would squeal without fluid and fail. I would start by checking the power steering fluid. If low or zero, then look for where the fluid might have leaked. Hopefully it is just a perished hose that you can splice and re-join. Perhaps on the bend behind the fog light position Quite common...

Check out the following thread. I've linked to a specific post in it which sounds exactly like the problem you have, but worth reading the entire thread after that as several other scenarios are mentioned. As you mention, it could be a seized pulley or tensioner has gone if the belt is still fine:

https://www.audiworld.com/forums/a8-.../#post24766237

It was very hard to see the fluid level so I poured in a little more to see, and it came to the brim almost immediately, so looks like there's no fluid shortage. With the battery having been depleted I took it out and charged it overnight and put it back in the car yesterday without ever switching the car on. I went out today when checking the fluid and turned on the ignition and the battery was again down to one bar? I'm at a loss as to what's draining my battery but does this point to a relay or something electrical?

If you charged the battery prior to putting it back in the car and never started it, and the MMI now shows just one bar, either the MMI is misleading or something is obviously draining it. That's usually some module that doesn't 'go to sleep' when the car is locked, so best thing is to scan the car and see if you can identify any potential causes (door handles are a prime candidate). Also check module 61 (battery regulator) for errors. Do you have a multi-meter to check the voltage on the battery?

I have a multimeter yes. I went out now to test the voltage on the battery and it's at 12.2V. I got into the car and turned on the ignition and now I see two bars on the MMI!. When I checked the fluid earlier I started the engine for no more than 30 seconds after I saw that the system did indeed have fluid and to check if I still had my PS issue (which I did). If the running engine charged the battery from one to two segments in that short time and now a couple of hours later the two segments (12.2V) are still in the battery then the battery drain must indeed be very slow.
The engine still turns and starts no problem with the battery at one bar on the MMI. but I'm thinking I can't have had this drain all along or my keyless would have stopped working long before now, so I'm al a loss where all of a sudden this battery drain has come from.

I'll need to charge up the battery again before a scan or I'll be getting errors all over the place.

Strange, so I charged my battery and it was 12.8V after letting it sitting disconnected from the charger overnight, but when I connected it back up to the car I had two bars on the MMI!!. I cleared all DTCs and did a scan and got...

-------------------------------------------------------------------------------
Address 01: Engine Labels: 059-907-401-ASB.clb
Part No SW: 4E0 910 402 E HW: 4E0 907 401 D
Component: 3.0L V6TDI G000AG 0020
Revision: --H05--- Serial number: AUX3Z0H1342405
Coding: 0011973
Shop #: WSC 02313 785 00200
VCID: 1E65DD6D3CB162BBF5F-804A
VINID: 9D196AAAA115188780042000249DC8F77E

1 Fault Found:



005715 - Please check DTC Memory of ABS Controller
P1653 - 002 -
Freeze Frame:
Fault Status: 01100010
Fault Priority: 0
Fault Frequency: 3
Reset counter: 255
Mileage: 237246 km
Time Indication: 0
Date: 2022.10.14
Time: 22:29:34

Freeze Frame:
RPM: 945 /min
Torque: 132.6 Nm
Speed: 0.0 km/h
Duty Cycle: 1.0 %
Voltage: 11.25 V
Bin. Bits: 00101011
Torque: 284.7 Nm

Readiness: 1 2 0 0 0

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 4E0-910-517.lbl
Part No SW: 4E0 910 517 J HW: 4E0 614 517 BQ
Component: ESP 5.7 allrad H49 0540
Coding: 0008357
Shop #: WSC 02313 000 00000
VCID: 2A0D01BD70F99E1B997-807E

1 Fault Found:
01826 - Sensor for Steering Angle (G85); Supply Voltage Terminal 30
000 - -

-------------------------------------------------------------------------------
Address 09: Cent. Elect. Labels: 4E0-910-279.clb
Part No SW: 4E0 910 279 S HW: 4E0 907 279 S
Component: ILM Fahrer H16 0240
Coding: 0143122
Shop #: WSC 02313 785 00200
VCID: 38292BF5BE553C8B1F3-806C

Subsystem 1 - Part No: 4E2 910 113 C
Component: Wischer WWS D3 H60 0440
Coding: 00000036
Shop #: WSC 02313

Subsystem 2 - Part No: 8K0 910 557 Labels: 8K0-955-559.CLB
Component: REGENLICHTSENSORH04 0002
Coding: 00139548
Shop #: WSC 02313

1 Fault Found:
00908 - Control Module for Wiper Motor
004 - No Signal/Communication - Intermittent
Freeze Frame:
Fault Status: 00100100
Fault Priority: 1
Fault Frequency: 2
Reset counter: 182
Mileage: 0 km
Time Indication: 0


----------------------------------------------------------------------Address 61: Battery Regul. Labels: 4E0-910-181.lbl
Part No SW: 4E0 910 181 C HW: 4E0 915 181 C
Component: J0644 BEM H12 0550
Revision: 00000000 Serial number: 00000000002093
Shop #: WSC 02313 785 00200
VCID: 2019E39506C5544BC73-8074

Subsystem 1 - Part No: 4E0 915 105 A
Component: von VA0 2802010529
Coding: 344530393135313035412056413032383032303130353239
Shop #: WSC 11111 111 45725

1 Fault Found:
00992 - Consumption Cut-Off Active
000 - -
Freeze Frame:
Fault Status: 01100000
Fault Priority: 7
Fault Frequency: 1
Reset counter: 255
Mileage: 237246 km
Time Indication: 0
Date: 2022.10.15
Time: 00:09:58


----------------------------------------------------------------------

The error code in Address 01 is because of the error in Address 03. The error code in Address 03 is because the battery has been disconnected. Once you drive the car for a short distance the code won't register anymore, but you will still have to go in afterwards and clear this DTC.

The error code in Address 61 may be caused by a faulty alternator. Check out the following page and in particular to the Service part, number 2. Not saying this is the cause, but worth at least investigating if only to eliminate it. I was wondering that since you initially lost A/C and power steering, both of which are driven by the serpentine belt and that also drives the alternator, it may be the alternator, assuming of course that there are no seized pulley or broken tensioner.

https://workshop-manuals.com/audi/a6...ulator/270606/

With the error code on Address 09, because it's intermittent, difficult to say what it could be. I'd focus on the other things first, clear the codes, and see if Adress 09 throws the same error again.

Mechanic has come back to me saying I need to replace my rack. Does anyone know if it's a definite engine out on a 3.0 TDI for steering rack replacement?

Having a quick read through the following PDF, it appears that engine removal is not required. Start from page 315:

39-Service Manual Running gear front-wheel drive and four-wheel drive.pdf

For future reference, you can find a host of PDFs at the following page (D3 Tech Dump):

http://forum.a8parts.co.uk/showthread.php?t=9347

The following post also mentions not having to remove the engine, although it may result in a lot of swearing:

http://forum.a8parts.co.uk/showpost....8&postcount=15

Thanks yes, I'd read that post before but couldn't remember was it here or Audiworld with the petrol engines. I have that PDF but as often is the way, sometimes a job can be done easier when not following the manual to the letter so I hadn't even consulted it. Thanks for the help.

OK, so my issue is getting curiouser and curiouser...mechanic tells me the PS pump is gone and rack is OK, but I now also have a battery not getting charged issue along with either the fanbelt or one of the pulleys fouling something where the mechanic is wondering if the engine mount(s) have allowed the engine to move forward slightly?? I'm really wondering how all these issues came about at the same time but mechanic tells me there's nothing wrong with the belt and no pulley is seized. I'm going to replace the PS pump to start with...

I never seen PS pump fail in such a way. Usually they either become noisy or start leaking. You have several issues that all point to belt drive. You say belt is still in place so maybe it is slipping. Have you or mechanic checked crankshaft pulley? It's 2 parts steel connected by rubber for vibration dampening. It's common failure point not just for Audi but many diesel cars, happened to missis Q7 3.0TDI and also friends A6 3.0TDI. Usually the rubber splits or becomes detached from steel and outer part just falls off but I suppose it might be possible that it stays in place just slips around. When there is little load, low rpm it might be turning belt but as load increases it just slips.

Maybe get another mechanic for second opinion.

I have attached the pictures of failed pulley from Q7. 1 both parts together and then separated

Thanks for the input. Yes indeed, the belt would tie all my issues together and although I haven't seen exactly what the mechanic is talking about as regards the fanbelt getting fouled, a crankshaft pulley failure like you describe may be causing the issue. As regards the PS pump itself - It had been 'moaning' intermittently over the past year or so, so I wasn't sure if it was the rack or the pump. I'll go back to the mechanic and try and get a proper look at what he's describing. He's adamant the pump is not working as he sees no fluid disturbance at the reservoir when he activates the pump.

Great call.
Had a look with the mechanic today and it's the crank pulley that's going in and out and fouling a metal pipe that runs behind the radiator. The belt and all pulleys spin away no problem until the steering wheel is turned and then the belt stops dead.
With these pulleys known for failing, does anyone know of any improved upgrade on the original?

Don't know of any aftermarket improved versions, but according to the parts catalogue, yours should be part number 059105251AD. It has been superseded several times, but it depends on specific PR codes, all relating to 'vehicle class'.

PR codes: 0HP,7JV
Most recent (2016) part # 059105251DJ

PR codes: 0CS,0HV,1CH,1CN,1CR,1CW,1CX,7JL,7JM,7JU,7JW,7KJ
Most recent (2018) part # 059105251DL

Yes they are known for failing.

There are revised versions, not sure if they are any better. I do not remember which one I had on Q7 but it was newer version than what it would have had from new but not the latest, genuine Audi item and still failed. I don't know how long it was replaced before. I think they are about £350 from Audi and aftermarket start from £60 if you are ordering from abroad and prepared to wait and can go up to the same £350 for aftermarket as well.

I got Febi aftermarket on eBay from UK for £100 as I did not want to wait for shipping from abroad. Also did not want to pay £350 for OEM as they are known to fail anyway and plenty of space on Q7 so pretty easy to change if it does not last as long as OEM and I need to change it again. A lot less space and harder to change on A6, not sure what it's like on A8 but if it's fouling a pipe and not falling off the I guess not as easy as on Q7

Thanks for the info Steamship. Yes I got that same part number from an online catalog and although I've not seen the actual part on the car, I've no reason to think it's incorrect. When I entered it in the search at https://www.oemvwshop.com/059105251dj-flywheel-p502770/
it came back with the same DJ suffixed updated part number that you quoted above, although I'm a little concerned as I only see Audi A8 up to 2007 mentioned. Then I also see that 059105251DL is listed for post 2010 cars only. Strange that the FL D3 is omitted from both lists.

Yes, I'm looking to go with genuine if there's no other upgraded part available, as it's front off to change it, so no small job. I'm going to replace the belt also and see if there's anything else I can do as well while I'm in there. Just in time for Christmas!!... :rolleyes:

From the official parts catalogue:
AD was available on the A8 from '04-'10

I was a bit vague with the DJ and DL ones in that the dates I gave is when they became available i.e. superseding older parts, but they won't necessarily show up in online searches as being suitable for an older vehicle.

Yes, I'd imagine the 059105251DJ part number applies to the end of the D3 run.
When I originally rang Audi with the AD number the guy told me that the part number had been superseded but wouldn't tell me the new part number!

I've just seen now on that OEMVWSHOP site that the AD original part number is listed under the OEM Part Numbers for the 059105251DJ part so I think happy days. Do you know if any bolts etc need to be replaced when putting the car front into the service position? Actually I'll have a look through the instruction PDFs.

Not very helpful as the official price is £283, so about the same as the one you linked to.

Sorry, never done any engine work on a D3.

Apologies for never wrapping this up - issue was indeed knackered crank pulley and car was back to normal after I replaced it with part I posted above.