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Audi A6 Avant blowing white smoke
I recently bought a 2007 Audi A6 Avant 2.0 TDI. It had previously been sitting idle for a month or two, but drove fine on the trip home. However, after a few days it struggled to start, before braking down completely.
I thought the battery may be low so attempted to jump start the car. When I did this there was a rattle from the passenger side of the engine and billows of white smoke out of the exhaust and the car then started to rev uncontrollably until I switched it off. When the car was checked the oil level had risen considerably and been contaminated with diesel.
It was removed to a garage where an oil and filter change was done and then left to idle (for a few hours) trying to get the smoke to clear. The result of this was it lost about 2.0-litres of oil just ticking over (no external oil leaks).
I don't know what is causing this and the garage don't seem able to diagnose the problem. They said that there is some underlying problem that they would need to strip the engine and it would be cheaper to replace the engine. What should I do?
I thought the battery may be low so attempted to jump start the car. When I did this there was a rattle from the passenger side of the engine and billows of white smoke out of the exhaust and the car then started to rev uncontrollably until I switched it off. When the car was checked the oil level had risen considerably and been contaminated with diesel.
It was removed to a garage where an oil and filter change was done and then left to idle (for a few hours) trying to get the smoke to clear. The result of this was it lost about 2.0-litres of oil just ticking over (no external oil leaks).
I don't know what is causing this and the garage don't seem able to diagnose the problem. They said that there is some underlying problem that they would need to strip the engine and it would be cheaper to replace the engine. What should I do?
Asked on 29 July 2016 by Pisgah
Answered by
Honest John
Two potential reasons for this. One is failure of the turbo bearing oil seals allowing lube oil into the fuel system. But on your description the most likely is that the Active Diesel Particulate Filter regeneration system is not working, probably because the filter is full of ash.
Active regeneration involves pumping extra fuel into the engine to exhaust out into the DPF, start a fire in there and burn off accumulated soot. But if the DPF is full of ash this won't happen and the extra fuel sinks into the sump, contaminating the lube oil and raising its level, eventually a point where, being a compression ignition engine, the engine runs uncontrollably on its lube oil instead of its fuel oil.
If the car has more than 80k miles on it, this is the most likely scenario. The DPF Active Regen might start working properly if you ahve the ash in the DPF cleaned out by the Ceramex process: www.ceramex.com/
Active regeneration involves pumping extra fuel into the engine to exhaust out into the DPF, start a fire in there and burn off accumulated soot. But if the DPF is full of ash this won't happen and the extra fuel sinks into the sump, contaminating the lube oil and raising its level, eventually a point where, being a compression ignition engine, the engine runs uncontrollably on its lube oil instead of its fuel oil.
If the car has more than 80k miles on it, this is the most likely scenario. The DPF Active Regen might start working properly if you ahve the ash in the DPF cleaned out by the Ceramex process: www.ceramex.com/
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