What causes common turbo failures on the Audi A6 diesel?

Against repeated advice in your column I decided to continue running my gorgeous Audi A6 diesel estate car beyond the three-year warranty period. 18 months later and just a couple of miles after the car achieved 50,000 miles, it ground to a halt on a very rainy A31 halfway across the New Forest. The car was towed to my local Audi dealer where it has been regularly serviced from new. The fault was identified as a failed oil pump drive which had consequently scuppered the turbo.

With no haggling, the dealership offered a substantial goodwill contribution, leaving me to pay a balance of just over £1000 for the repair. According to my research of the internet, it appears that similar breakdowns on 2.0TDI engines are fairly frequent and attributable to two types of defective engineering of the oil pump gear, depending upon engine type. Virtually all of the cases discussed affected cars at 50,000 to 60,000 miles. When I collected my A6 following repairs, I was reassured by the dealer that the replacement parts have been subject to improved design and the chances of any recurrence of this problem are therefore unlikely. To date there has been no recall of cars with the original oil pump drive and this must mean that there are a large number of VAG diesel cars on the road with the potential for similar oil pump disasters.

Asked on 13 April 2013 by RP, Bridport, Dorset

Answered by Honest John
It's an old problem. It the oil pump fails it’s like heart failure because oil is no longer pumped through the engine and the turbo bearing is the first component to fail. The malady mainly affects 2005-2007 2.0TDIs in A4s, A6s and Passats, all detailed in the various VAG entries in www.honestjohn.co.uk/carbycar, but not the commendable treatment you received from your Audi dealer, so I will now include that as well.
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