DPF has gone quiet

[suzannec]

So over the 5 years of ownership of my 1.6 TDI I've grown used to the car sounding like a jet when I turn it off. I soon realised this was my diesel particulate filter rather than the engine fan. I generally drive journeys of at least 30 minutes at motorway speeds sometimes further, car has approx 75K, no dashboard warnings.

Over the last week or so my car has been quiet when I turn it off. Should I be worried?

The DPF went on my old Volvo C30 and that was an expensive job, it had similar mileage when that needed doing.

 

[Carefree69]

My previous 2.0TDI with dpf would only regent once in a blue moon, so I never got alarmed when I didn’t hear the fans after I switched off.

By the sound of it your regen’s happens pretty regularly, I could be wrong but I’m not sure that’s normal if I’m honest.

 

[SamR92]

Mine comes on at most 1 or 2 times a month, which as far as I’m aware is normal. Usually when it comes on all the time it’s because the journeys are too short that it’s not had enough time do clear as your driving

 

[Ormesome]

I have the same engine as you. If I do small journeys of around 10kms each day for a week, she lasts around 2 weeks until I get the dpf regenerating. However, sometimes its longer and generally depends on how long I drive. Compared to other cars iv driven, the A3 seems to regenerate very quickly and quite smoothly. I would say that your car is regenerating on the motorway and your not realising it. The other times it might have got to the regen stage when you are close to home/work so you hear it continue when you turned the engine off. Don't forget to think about the times of the year, your car will be taking longer to heat up at the moment as its winter so the chance to get to optimal temp to make a regen will be lower than in summer for example. My car takes a while to heat up at the mo but it is -2 in the day and -10 at night!

 

[suzannec]

Useful feedback, thanks all.
It actually regenerated this morning when I got to work. I think I had got used to it doing it extremely regularly and just couldn't remember it doing it in ages. Relieved. Hadn't considered temperature either.

 

[DrMal]

Useful feedback, thanks all.
It actually regenerated this morning when I got to work. I think I had got used to it doing it extremely regularly and just couldn't remember it doing it in ages. Relieved. Hadn't considered temperature either.

There's an awful lot going on in the engine ECU when it's deciding when to regenerate and then during the regeneration process. During a DPF regeneration cycle, electrical loads will be turned-on but not shown to the driver (e.g. heated rear window) to put more load on the alternator, make the engine work harder and increase exhaust gas temperature. The engine ECU will probably also produce some "post" injection fuelling to inject straight into the exhaust gas stream. This is all designed to burn the particulate matter in the DPF.