spartacus 68

Glow plug 4 is cylinder 4, so typically furthest from timing belt on 2.0TDI. Personally, I’d be changing them all. Think OE is Beru and uses either deep 8mm or 10mm socket. Spray penetrating release such as PlusGas on all plug seats a few days prior to work and only once car to operating temperature. Use 3/8” or 1/4” ratchet, and don’t over-leverage. If it snaps you’re in a world of pain. Use smear of ceramic grease on new threads. Ensure the cylinder bore is spotless, you might need a vacuum cleaner to suck up any debris first, then microfibre rag on a flat head after removing plug. If not confident, leave it to a garage.

Annual servicing all day long, but certainly every 10k miles.
Audi moved to long service regimes because they were shifting cars with finance and offered free servicing as an incentive. They also introduced it to seduce fleet dealers who hoped to reduce their running costs.
The whole thing is a fallacy. The reality is no synthetic oil can retain the lubrication properties to protect an engine after 18k miles. Down the line, an unsuspecting new owner will buy an ex-fleet or leased 3-4 year old car and discover premature engine wear and pick up the bill.
For all the costs of an oil filter and 5-6 litres of fresh oil, just change it. I personally do it every 5k miles, still use Castrol Edge 5w30 LL, but my 2017 plate 3.0 TDI Allroad will be my last diesel.

Good news. Swap out the sensor. Get genuine part, not an Ebay special. Shouldn't be that expensive.

I don’t know exactly how this works, so just pointing out a few of the pitfalls as I see them. Feel free to correct me if I’m wrong. Even if you’re not claiming against your own insurance, they need to be informed, or you’re in breach of contract, and insurers talk and share information. If it’s a cover thing and the terms of the policy wouldn’t pay out anyway, then that’s different. Again I suspect you’ve had that conversation already.
As mentioned, avoid main Audi dealer. This is not their area of expertise. Some main dealers will have affiliated body shops, or even their own body shops to help prepare or repair cars prior to sale. They also use a host of other businesses for everything from refurbishing alloys to paintless dent removal.
That said, you do get Audi approved bodyshops, ones where the franchise brand recognises the standard of workmanship and the business use OE parts, OE paint and observe certain repair processes. Details here: https://audiapprovedbodyshoprepair.co.uk/audi-approved-repairers/
For whatever reason this can’t be claimed against the insurance, then you’ll know it’s going to be expensive. On a 2025 S3 which probably retailed for around £40k, if you cut corners on the repair to reduce costs, then you’ll ultimately be hamstringed if or when you come to sell it.
Without seeing the damage, it’s impossible to say how much. Even paint on a couple of doors you’re looking at a £1-2k easily. With new doors, they need to be built up, electrics, trim, even if you’re swapping over. Certain trim pieces, the bodyshop will just buy new, they won’t strip off parts and refurbish.
Anyway, get a few quotes and build in a contingency budget. It’s often when work is underway you get a call because they’ve discovered something broken. Even things like alloy wheels could be bent and need replaced.

I’m on my second A4 Allroad and can recommend. They’re not that common, and are generally well built.
B8 cars were produced from (2008-2012), with B8.5 facelift (2013-2015), and B9 (2016-2024).
First things first, these cars have multi-link suspension, which is coil springs and alloy arms. If you want air suspension, then you’ll need to go down the A6 Allroad route. Generally suspension is fine until around 100k miles, but some are hydra-bushes, so check the servicing.
They do have increased ride height, and body cladding on arches, although I’ve seen models where the plastic panels are painted.
I used to have a 2012 B8 A4 Allroad with 2.0TDI (177PS) with 6-speed manual, that would have been Euro 5.
I now have a 3.0TDI (272PS), Euro 6 of course, plus it has bullet-proof Tiptronic 8-speed transmission. It’s very comfortable to drive, fast when you need to be, and because it can lay down 600Nm of torque with permanent 4x4, then it’s happy hauling a loaded trailer too.
The B8 was a good introduction, but if you’re going for diesel, then it will be Euro 6, which means it meets clean air zones in cities. To do this it has AdBlue, DPF, EGR and catalytic converters. If these go wrong it’s expensive. On every AdBlue top up, I add Forte anti-crystal to reduce likelihood of issues.
I think the B9 is reliable. I do my own servicing, so change the oil every 5k miles, but generally, no more than 10k miles.
On current 2.0 TDIs, I think they are 190PS, and will likely be paired with S Tronic 7 speed auto box. The transmission needs serviced every 38k miles religiously.
The 2.0 TFSI cars are rarer, but use Haldex system if I’m not mistaken (Quattro with ultra technology), so 4WD engages if it loses traction. That needs serviced every 20-30k miles. Power wise I think 252PS (up to 2021) with 2024 models achieving 261PS (badged as 45TFSI, plus it’s mild hybrid (something else to go wrong in my book).
Work out what extras you want. Audi went down pack or bundle routes years ago, but they can be tight.
Retro-fitting anything is expensive, so draw up a shortlist of things you can’t live without and go from there.
If your budget allows, then Vorsprung includes everything such as 360 degree cameras, matrix headlights, lane assist, but these cars will be £40k price bracket.
My advice, avoid any car on a long service regime (up to 18k miles between oil changes), or you’ll pick up the bill for engine issues down the line.
On 2.0 diesels, they will be cambelt, so 5 years or 60k miles, and renew water pump too. 3.0 litre diesels are chain driven.
 
 

Not asking why you’re going from bi-xenon to LED which seems retrograde step, but this should help. Should be in driver’s footwell where relays live on right-hand drive. https://www.lllparts.co.uk/catalogs/audi/RDW/A3/412/9/941/941025
 
On bi-xenon you’ll have headlight self levelling on passenger side front and rear suspension. Not sure if you disable this module you’ll disable headlight wash too?

If CNHA engine, it’s located on engine block cylinder head. Also known as hall sensor (14) on this link.
https://www.lllparts.co.uk/catalogs/audi/RDW/A6/717/1/103/103052
Crankshaft sensor here too (15) near bell housing: https://www.lllparts.co.uk/catalogs/audi/RDW/A6/717/1/103/103050

It's quite difficult to determine a wheel bearing on a quattro in my experience. I've rarely identified a wheel bearing based on holding the road wheel at 10 to 2 position or trying lateral movement. In addition I don't think it's the brakes. You can generally rule out the brakes and a sticky piston by driving for a few miles and coast to a stop. A sticky piston or contact on the pads and the disc and will heat up rapidly.
Normally I've had to strip down the brakes to get to the hub, then rotate. It's normally fairly obvious at that point. If you've already renewed the N/S/F, then chances are the O/S/F if it's original has gone. Pretty sure SFK and F.A.G. are the same plant. I tend to opt for F.A.G. given labour to replace.
Now the hard work - this can be done on a drive, but a word of warning - that bearing hub will be corroded to the strut housing with aluminium oxide. You'll need a air hammer or similar to shift it.  The front axle hub bolt will need be torqued up too, so make sure you have a 3/4" breaker bar. 1/2" will likely bend or break.
Dave Sterl does a cracking video to millustrate. 
 

Remove the existing switch and take a closer look. You need to quote the Audi part number. There will be one, trust me, somewhere.
Back to sunroofs - there are notorious for leaking at the drains or the actual tray cassette, so check the switch for corrosion on contacts. The motor or micro-switch can also fail. The fact it's still working means there's 12v current, so likely to be a contact issue rather than a failed motor.
https://www.lllparts.co.uk/catalogs/audi/RDW/A3/201/9/959/959000
In my experience if you remove the motor - you many need to go through a relearn sequence as there's probably pinch-protection on the roof.
The actual switch is part 4A on the LLL parts diagram. I checked parts for a year 2000 model and they are exactly the same, apart from colour code of interior. New one to me - called a Potentiometer (sounds like it should be used in the film Back to the Future!)
If it's standard grey - this work? https://www.newmiltonautoparts.com/4b0959613b--a-genuine-audi-a3-4-a6-a8-sunshine-roof-sunroof-switch-13549-p.asp

You're right, apparently started around 2007/2008 on B8 A4 model. With that in mind - just plug and play!
 

I think there's a little more than swapping like for like and suspect you'll need VCDS v OBD11. If the headlights are second-hand then there might be component protection on them, given units new are £2k for each headlight. If that's the case, then you're looking at dealer-level software such as ODIS to remove.
Starter for ten look at parts on LLL parts and compare LED with LED Matrix.
https://www.lllparts.co.uk/catalogs/audi/RDW/A3RS3/596/9
Also search Kufatec, they supply additional wiring or complete headlight kits.
https://kufatec.com/en/led-matrix-headlights-with-led-drl-and-dynamic-blinker-for-audi-a3-8y/49200
You could take the hassle out of this and simply go to an Audi retro-fitter.

Speak to Adam at AV Adaptions (Aberdeen).

Suspect the plastic lever is on the underside of that electrical connector, normally press the tab and pull the plug at the same time. You can use a flathead screwdriver against the side of the expansion tank and the sensor and tease it out. Don’t use force.
 
More details here. 
 

Go to a professional body shop. Had a similar issue with an old 2012 A4 Allroad. It’s classed as Platinum Grey 1RR, however will no doubt vary across models. When I spoke to Audi main dealer, it didn't even show up as a code.
Phoned a few body shops and ones that are Audi and Porsche approved and they said it can’t be blended. Entire panel would need to be painted. As it’s matt/satin effect, it’s notoriously difficult to achieve consistent effect with rattle cans. Hope that helps.

Don’t skimp on budget is my advice. I understand you’re looking at B&O, but that needs to dovetail with car model, engine and gearbox and even colour.
B&O was expensive feature, so it’s not likely to be found on poverty spec car. If you find B&O, then it’s bound to have leather, folding mirrors, possibly virtual cockpit would be my experience. Retrofitting anything is expensive, and usually you need VCDS to remove codes, even if plug and play.
I know this is on an Allroad brochure (2017), but it elaborates on the comfort and sound packs. https://autocatalogarchive.com/wp-content/uploads/2017/09/Audi-A4-Allroad-2017-UK.pdf
 
Trim level aside, you want history and lots of it. On cars that have been on long service intervals, personally I’d give them a wide berth. No oil should be in the car for 18k miles.
Be prepared to travel too, once you’ve done your due diligence checks. Additional checks such as Car Vertical which you pay for are useful.

Pretty sure you'll need to undo drive shaft bolt and remove lower balljoint so you can withdraw driveshaft and CV from hub to see. A wobble impact triple square is handy. See videos for Dave Sterl on YouTube. He's done A4, so can't see A3 being different. You'll need a new driveshaft bolt, and torque with wheel off the ground. Bearing wise, F.A.G. every time. Make sure hub face is spotless before fitting. Wire brush attachment on a drill, that sort of thing.

Check exhaust clamps, and flexi (if one is fitted) these can corrode and what you’re smelling is fumes from engine bay. Also auxilliary drive belt, a seized clutch drive pulley, etc.

Speak to Tomas at VAG Technic. Oxfordshire to Dudley is about 1hr 30mins away. They drop performance engines all the time and know their way around S4. I’m sure there’s logical explanation.

Yours will be 2.0 litre 252bhp version if Quattro. Its a chain. Technically speaking there’s three.
If it’s been on long service intervals, get off of that and into oil changes every 8-10k miles.

Laser make conical locking wheel nut extraction sockets. Find one that fits over it, hammer on (needs to be tight) with lump hammer, and extract. Better with extension breaker bar than a power tool. If you’re not confident, just take it to a garage.

It is cam chain. No reason to replace unless you have rattle at start up. Regular oil and filter changes will help keep the engine in good condition, ideally around 8k miles. Ignore long life service regimes, that’s what kills engines.
If for arguments sake it needed replacement chains, guides, sprockets and tensioners, it’s an engine out job. Check out VAG Technic on YouTube. On performance Audi RS and S models, they are constantly stripping them down due to premature fault with rocker arms and needle bearings. 
In terms of maintenance then pretty sure this is 218 is S Tronic 7-speed box. Needs gear oil and filter change every 40k miles. Fuel filter every 20k miles. Once you get to 100k miles, treat rear diff to a fluid change.
Worth investing in VCDS even if you’re not spanner handy, as will pinpoint fault codes, and useful for things like coding battery, etc.
Gave up on main dealers years ago due to ludicrous costs. Find a trusted garage that knows these cars inside out. It’s got air suspension which is pretty robust.

80Nm + 90 degrees for the bearing and carrier triple square bolts. Personally only fit a quality bearing, such as F.A.G. or similar, that will be OE. Make sure the hub face is spotless before torquing up the new bearing and carrier flange. There will be aluminium oxide when the old one is removed, but a wire brush assembly on a drill is perfect.
For the driveshaft bolt, it’s 200Nm plus 180 degrees. Importantly, the axle cannot be on the weight of the vehicle. More details here. 
 
 

To be honest there’s zero value in it. It’s worth more to you than what’s it’s physically worth. I used to have B5 2.5TDI Quattro Sport Avant, and took it to 175k miles. The B5 shape is attractive, especially in avant form. I still search for mine on UK MOT check and sadly its MOT was never renewed after Jan 2024 at 222k miles.
You do see these cars from time to time, especially in southern Europe where they haven’t been ravaged by our winter road salt. The V6 diesel version is fairly bullet proof. 
If it were me, and depending on budget, it would be an interesting project car to completely strip and rebuild. There was something on a different forum with a B5 in Hibiscus Red. However if you’re not spanner savvy, then costs will run away with you. VCDS software is very useful too.
Subframe front and rear would probably need to be dropped, new bushes and powder coated. New Meyle HD multi link suspension all round, probably new dampers, brakes overhauled. Interior wise, should be easier. The matrix dash used to be problematic but can be fixed, plus unsightly scratched interior controls where the rubberised paint has worn off.
Then there’s the small matter of a new paint job. Madness, probably, but if it’s part of the family, keep it.