Audi A6 Allroad, C7 or C8?

[ChrisP]

Some advice please, guys n gals,

I have owned a 2015 C7 AUDI A6 3.0TDI 215bhp Allroad since 2018, and have taken it from 40 K to 130K initially with main dealer servicing, and latterly the village garage (-who had previously looked after a couple of my BMW 525iX's very well).  Things started going downhill, since when it has felt that the car has owned me, just over a year ago when the Audi 'threw' a diesel injector. Both that injector, and another found leaking on inspection, were cleaned and reseated, and their stripped retaining bolts' sockets heli-coiled back into the cylinder head (-and new bolts used at my insistence, given the torque-tech issue). The same problem had occurred with another injector two years before -an unsettling, but in the event, a durable repair. 

However, on the latter occasion, a smell of diesel persisted, about which the garage said they weren't surprised and reassured me, citing heavy prior cylinder head diesel contamination. MPG was satisfactory on a 140-mile test drive, to Bristol and back, and I set out on a trip from Worcestershire to Scotland to see a newborn granddaughter. 

Just short of Tebay, the steering suddenly became oddly uncertain, traffic density was thankfully low and, in drizzle at dusk, I slowed to 40mph without braking on a serendipitous stretch of uphill gradient, and gently eased the vehicle into the nearside lane, whereupon it suddenly spun anticlockwise thro 180º and then, pointing south, slammed its offside into a nearside crash-barrier along the hard shoulder, incurring modest damage to front and rear offside wings. 

No other vehicle was involved. Highways Agency recovered me to some nearby off M-way services, the police remarking on a strong smell of diesel, as well as noticing diesel on the road under the car. The Highways Agency recovery man complained that the diesel transferred to the soles of his boots lubricated them on the rubber pedals of his truck. 

I called the AA, to diagnose the source of my diesel leak, my hoping that were this identified and fixed, then I might be able to drive the vehicle home, safely. The insurers' flatbed truck was otherwise going to take 48-72hours. The AA identified a loose (ie completely detached) low-pressure diesel return pipe as the source, then left the scene saying they shouldn't have attended a vehicle involved in an RTA. Left to my own devices, I reattached the diesel return, using a cable tie to secure it. After testing the steering on a few circuits of the now deserted services' parking lot, tyres dry and diesel dissipated, I gingerly headed back down an empty M6 at a sedate 50mph, my arriving uneventfully home at daybreak. A new OEM diesel return system was duly fitted and the bodywork repaired by the insurers. And then another injector reseated.

The body-shop remarked upon an engine oil leak, for which a cracked offside rocker-cover was blamed and replaced. However, the oil leak persisted, and the garage fingered a leaking front crankshaft seal. They stripped off the front of the car for access, removed the pulley, replaced the seal and then put everything back together again. About 50 miles later, the Audi invited me to top-up the engine with a litre of oil... Pulling off the M5, I could see the front crankshaft seal dripping again. Reading about the subject, I noted that a £75 Audi special tool was recommended for the seal replacement job, as well as the use of some high-temperature superglue at £40/tube. I sourced a Victor Reinz OEM seal, which was handily supplied with a bespoke plastic disposable fixing tool in the box, and ordered the expensive special glue. The Seal was replaced a second time by the village garage and, at my instigation, the rocker cover CCV apparatus on the nearside bank checked for blockages.

Before I could replace the car, an AdBlue System Fault advisory appeared on the instrument console with '650miles to no restart'. Diagnostics indicated an intermittent NOx sensor fault. Replacement corrected the NOx sensor diagnosis, but the AdBlue System Fault notice persisted, along with an illuminated orange engine light, further diagnostics indicating an ostensibly new 'low reductant pump pressure' fault. The AdBlue injector nozzle appeared 'as clean as a whistle'.

Time for a visit to the main dealer. They confirmed the 'low reductant pressure' error, and whilst discovering that the Adblue pump is physically working, with measurable output, they suspect a defective pressure sensor, an integral part of the pump and have recommended pump replacement (£800 + Labour @ £169/hr + VAT). Inspection also leads them to suspect an ongoing oil leak, as well as a mysterious coolant leak (-pink liquid was identified in the engine 'V' as well as dripping beneath the car, where admixed with oil, it besmirched their workshop floor). Coolant level in the expansion/top-up tank was satisfactory. Another injector was leaking, btw. Divers other sundry issues were identified. They appeared quite shocked; I was sad. 

When I have had the AdBlue pump replaced, the ECU reset, the question of the oil and coolant leaks sorted, and the injector reseated, it will be time to dispose of the vehicle and buy a younger model. For various reasons, I genuinely need an A6 Allroad, so the choice lies between another slightly later (eg 2018) low mileage (eg 30K) C7, or a somewhat higher mileage C8, my planning to spend £25-30K. Fortunately, I do not need to sell the good sense of this to a significant other.

So here's the question: how much of this tale of woe is down to recognised age-related C7-specific problems which I might avoid with a C8? Or might a leap into an even more technologically complex' C8, whilst avoiding groundhog-day, be a frying pan-fire job?  Either way, I'm thinking entry-level, not biturbo.

Obviously enough, I'm posting this in both the C7 and C8 forums.

I look forward to folks' opinions and considered advice.

Thank you,

Chris Poole

[Steve Q]

Sorry to hear of your situation. I don't blame you for wanting to change the c7 I'd say drive a c8 and see what you think. The fact it's newer would help improve reliability.