Audi A6 TDI buying advice

I can't see a 2.0TDI A6 being any more economical than a 1.6HDI 407. The 407 should actually be pretty good on fuel so if you aren't getting good economy figures then there may be something wrong with it.

The 2009 model has the newer common rail engine which is smoother and more economical than the older PD unit. If you could stretch to a common rail version it would be a good idea. 2008 was the changeover year, either engine could be fitted to a 2008 reg car.

If you are buying a 2007 A6 2.0TDI you need to read up on the oil pump/balance shaft issues associated with that engine. On a 2007 car it can be solved without huge expense but it still needs to be factored in when budgeting for the car. There are a few threads on here about it if you do a search.

Saab Ed wrote: »

+1

And thats just the start of your worries. I'm always baffled with the residual values of these cars. The problems they give, for a car supposed to be of such a high standard, is just mind boggling. Flywheels, electrics, heaters failing, the oil pump/balancer shaft issue already mentioned are all very scary and expensive issues with these already over priced cars.

Every modern diesel gives flywheel trouble so it is unfair to single out a particular model for criticism IMO. The A6 gives comparatively little flywheel trouble compared to a 1.8TDCI Ford, for example. They are actually a pretty solid and reliable car apart from the 2.0TDI PD engine issues (which admittedly are significant).

The OP being a 407 owner will be well used to electrical and heater issues anyway :pac:

Anything from 100,000km upwards is danger territory for the balance shaft issue although equally I have seen them with 200,000km on them with no problems at all so it is down to luck really.

There are two separate problems which affect the oil pump/balance shaft unit in the 2.0TDI engines as fitted to the A4 and A6.

The early cars (up to mid 2006 or thereabouts) used a chain drive from the crankshaft to the balance shaft/oil pump unit. The plastic tensioner on this chain breaks which leads to wear on the chain sprockets and eventual failure of the oil pump drive system, with predictable results.

VW obviously became aware of this problem at an early stage in the production run because from mid 2006 the drive system was changed from chain to a more reliable gear setup. They stopped supplying spare parts through the dealer networdk for the chain setup (although they are available from other sources) so many early cars that suffered chain failure were upgraded to the later gear type system.

Unfortunately this is only one problem with the oil pump drive. The other is the hex drive for the oil pump. The gears only directly drive the balance shaft. The oil pump is situated at the end of the balance shaft where it is driven by a hex shaped bar. About half of the total length of the bar is in the oil pump but it only extends into the end of the balance shaft by about 25mm. For some reason the bar is quite a loose fit in the balance shaft which means that over time the corners wear off until eventually it gets to the stage where the balance shaft is spinning as normal but the oil pump isn't being driven. Once this happens turbo failure will be almost instant and engine damage will result if the car is driven for any length of time.

Pictures below of a worn drive bar. This was removed from a 2008 Audi A6 @ 129,000km as a preventative maintenance measure.

The wear on the end of the shaft is clear to see. This probably would have failed within a short space of time if it hadn't been removed.






The newer balance shaft assembly is slightly improved in that it features a longer drive bar which extends further into the balance shaft which should extend the mileage they do before wearing out. But it is just a modification of a crap design rather a proper cure for the problem.

We do loads of these both as repair jobs and preventative maintenance jobs. We are seeing a lot of cars recently with damage not just to the hex bar but to the balance shaft itself where the hex bar fits into it. A couple of years back when this happened the only option was to replace the entire assembly at a cost of circa €1100 + VAT for the part alone. Luckily there is now a company in NI called Powermax Engineering who fit a hardened insert into the balance shaft which is a permanent solution to the problem. I have before and after pictures of one of these repairs here somewhere I will dig them out and post them shortly.

To have this repair carried out as a preventative measure would cost you in the region of €650 for parts and labour.

There is no way of knowing when it will happen. There are other companies that repair the balance shafts but Powermax are the only company that I would trust to do it as I know they have the track record.

Powermax only do the actual machining of the part, the removal and refitting has to be done separately by a garage (or DIY if you are into that sort of thing)

The parts can be gotten in advance so no delay there. It is about 4 hours work to fit for someone who is familiar with them.

The newerCR engines were introduced in late 2008 when the A6 got a facelift. Very few 2008 facelifted models about and there are a good few 2009 prefacelifted about too.

The main cosmetic differences are that the facelifted model got redesigned bumpers and lights which include fromt LED DRL's and rear LED lights, and side indicators moved to the door mirrors.

Prefacelifted A6 rear:



Facelifted A6 rear: