Recurrent oil leaks in a 2015 C7 A6 Allroad, 3.0L TDi 218hp

[ChrisP]

Hi Y'All,

I initially posted this yesterday as a follow-up to my original Adblue issues, whereas the help I need relates to a different problem, namely recurrent oil and coolant leaks. I've therefore belatedly reposted it here. Apologies.

Since 2018, I've had a 2015 post-facelift A6 C7 3.0L TDI V6 Allroad which I've taken from 40K to 130K miles, initially with main dealer support, and latterly that of the village garage.

Having just had had some Adblue system faults expensively fixed (-new NOx sensor in the villlage, and then a Adblue pump new pump and ECU reflash by a main dealer), I'd now quite like to unload it, However, it has some very obvious oil and coolant leaks, presently unsorted, for which I'll naturally take a hit price-wise. These include leaks from around the sump's retaining bolts, ongoing leakage from the front crankshaft seal (-replaced x2 this last year), as well as oil and coolant into the 'V' from the cylinder head gaskets.

Having had these issues looked at by an independent 'Audi Specialist', they feel sure that problems of this extent speak to underlying raised crank-case pressure as a cause. The specialist was also surprised by the vehicle's history of having blown no less than 5/6 diesel injectors over the last couple of years (-each requiring reseating with new retaining bolts and seals, several of the retaining bolts' cylinder-head sockets having needed to be heli-coiled in addition). In fact they say they cannot recall another 3.0L V6 TDi in any VAG vehicle which has thrown so many. But what amazed them more was how smoothly the car runs and, in respect of poke and economy, I cannot fault it myself either. For the record, I've never let the oil level drop much, having always acted promptly on the instrument console advisories.

Potential causes of raised crank-case pressure obviously include include leaking piston rings and crank-case vent problems. However, I cannot believe, given the above feel-good stuff, that the underlying issue is leaking piston rings. Furthermore, in respect of blocked crank-case venting, I had one oil-leaking cracked (plastic) rocker cover replaced last year, and the other, and its integral PCV, rechecked and declared OK just last month.

Reading round the subject of raised crank-case pressure in the VAG 3.0L V6 TDI on line, I'm afraid I've drawn a blank in respect of this being a common or inevitable problem, even in higher mileage vehicles. Any ideas as to its likely underlying cause would therefore be gratefully received. The Audi Specialist indicted the blow-back around the car's previously loose diesel injectors, but I didn't entirely follow the physics.

Needing another A6 Allroad I can rely on, I've just bought an immaculate (2018) A6 C7 3.0L V6 TDI, with just 26K on the clock and I'd like to do everything possible to mitigate the risk that it too might also suffer such problems as it ages. I'm also inclined to take out an AUDI service plan and extended warranty to manage the unexpected.

All insights gratefully received.

Thank you.

[Steve Q]

Extended warranty is only worth doing if it's a genuine Audi one and not an independent company as most of them aren't worth the paper they're written on. 

Your new allroad sounds lovely 🙂

[ChrisP]

Hi Steve,

Yes, I was going to look at the Audi Extended Warranty, and the their service plan, given the car's relative youth, mileage-wise & condition.

Thanks,

Chris