Time for a DPF Clean?

[mrcheeezy]

2014 Audi A7 3.0 TDI 205k miles

All seems fine with the DPF regen’ing itself every 300 motorway miles and normal DPF pressure readings. I did a routine VAGCOM diagnostic with service and it says fault 5585 DPF blocked. I noticed the oil ash volume was 0.39L which I think is above the threshold hence the fault code?

My question is - do I need to remove the DPF to clean it or can I do an ‘on the car’ clean adding cleaner via the temp sensor port? Do any of the of the shelf cleaners work or do I need to take it to a specialist DPF cleaner?

many thanks for any advice.

IMG_4584.jpg

[mrcheeezy]

Here’s a pic of the fault code:
Attachment 39440

[swalker]

I would like to know also
Your different pressure is at 8hPa, i hear this should be <5 at tick over and less than 50 at 3kRPM? to be confirmed.
I believe, but again don't know for sure - the cleaners will sort the soot out but not the ash?

[mrcheeezy]

Yeh mine is normally 5 at tickover and about 35 at 3000 rpm. It hits about 200 at full power in sport mode which I try to avoid. I’ve noticed it varies with the engine loading (going uphill or accelerating) as the fuel flow increases which I guess makes sense.

What is strange is when it regens the soot never drops to zero but stops at about 4g (not sure how it calculates it) - I was wondering if this represented the oil ash / soot it can’t burn off as I assume it can’t actually measure it but just calculates an estimate based on useage?

[mrcheeezy]

So finally got round to removing the DPF and getting it professionally cleaned. Removing it was ok apart from the one exhaust nut that has to be accessed from below - this bit was a 2 man job really as one to hold the socket onto the nut on the lower DPF flange and one underneath the car to undo the nut. I had to use 2 long extensions and a universal joint but it worked - definitely not a nut to round off as can't see how you could recover as no access.

The results from the DPF clean was:

Before:
Flow rate: 222 m3/h
Back pressure: 34 m/bar

After
Flow rate: 415 m3/h
Back pressure: 6 m/bar

The DPF had done 200K so the before results were not surprising and a Lot of ash was removed (lots of motorway miles and shows good regens apparently).

Anyway refit it today so it will be interesting to see what vagcom says.

[Crasher]

Do a service regen when it is back on.

[mrcheeezy]

So all seems good. Did a DPF reset after refitting DPF to clear the computed Ash value. After this it said it needed a regen so took it for a drive and regen'd fine. Thanks for the tip on service regen Crasher , it reduced the remaining measured soot value to zero and calculated soot to 4g (assume this is normal - not sure why the difference between calculated and measured?). Temps got high (620 deg c and some very hot smells from the exhaust - thought I was going to melt the tarmac!!). Anyway DPF pressure now reads 2 to 3 hPa on idle. Long motorway drive tomorrow, so will be interesting if MPG etc improves.

I'm also pleased I managed to retrieve with a magnet the 12mm socket that dropped into the v when removing the DPF!!