Evening all!
Back in the summer I bought myself a 07 plate Octy 4x4 tdi to replace my trusty Mk1 tdi. For the first few months, all was well but recently the car has become noisy at motorway speeds and while accelerating. The noise sounds rather like a blowing exhaust giving a definite 'boom' inside the car. I've had it serviced recently and asked the dealership to check the exhaust (as well as consider the problem generally). The booming is accompanied by slight vibration and appears worst between 1800 and 1900 rpm as well as between 2300 and 2600 rpm. If you turn your head, it appears to be coming from the rear of the car. If you come off the throttle, the booming noise may occasionally persist for a second or two before disappearing completely.
I towed a large trailer up to the far north of Scotland back in October and whilst chugging up motorway hills in 5th at 65mph the cabin was really quite noisy. Very different form the car I purchased back in July.
As this problem has progressed, the fuel consumption of the car has steadily got worse. I was originally getting 50-53 mpg (I know, granny mode!) on the morning run to work, now I'd be lucky to get 46mpg. Long runs on the motorway at 80mph+ used to yield 47mpg. Now we're down at 42 or 43. On back roads (with no 'booming') the car is still very efficient.
The dealership handed me a can of Castrol diesel flush. Alas, no improvement. A pity, has I thought this most likely to be an injection problem.
I've seen posts elsewhere on this execellent site regarding 4x4 gearbox problems, a worrying thought. However, the car has performed well in the recent snows, tackling some very slippery inclines with ease. Exactly why I bought it really.
The car is now at 82000 miles and is otherwise in good condition. The only other complaint I would have is that acceleration in 1st has never been that great, whilst in 2nd and 3rd, is accelerates well. Perhaps pointing at a gearbox problem?
Any thoughts or suggestions gratefully accepted!
N2B
