Black Soot

[alfy1987]

Evening all

I’ve searched the forum but can’t seem to find a common thread.

I have a 2016 2.0 T6 BMT, I’ve noticed recently that after cleaning the rear wheels and bumper they quickly become built up in a black soot (shows up easily on the white!). Even more so when I drive with the engine under load.

I’m by no means an expert but after reading a few posts I assumed this would be unexpected with the DPF... assuming I have one?!

Just to add to, on the weekend when I started the van it felt like it was running on three cylinders for a good 60s before returning to normal. This only happened once and hasn’t reoccurred since.

I’ve brought the carista OBD reader but this didn’t throw up anything meaningful.

Any guidance would be appreciated.

 

[Tourershine]

Just to add to, on the weekend when I started the van it felt like it was running on three cylinders for a good 60s before returning to normal. This only happened once and hasn’t reoccurred since.

Out of interest, had the van been sat for several days when this happened?

 

[Loz]

Do you have the “short” exhaust?

 

[alfy1987]

Out of interest, had the van been sat for several days when this happened?

No it’s being used daily.

 

[alfy1987]

Do you have the “short” exhaust?

What’s the best way to check that?!

 

[Loz]

The short one ends before the rear wheel the longer goes right to the rear bumper.

 

[alfy1987]

The short one ends before the rear wheel the longer goes right to the rear bumper.

Just had a look, I have the longer exhaust

 

[Loz]

So it is more likely its brake pad dust then, mine nuked a set of rear pads in 16k miles.

 

[alfy1987]

So it is more likely its brake pad dust then, mine nuked a set of rear pads in 16k miles.

Wow really!

Here’s what I’m dealing with!

 

[Loz]

You will get soot(ash) pumped out during a regeration, but normally you are driving so it should all be going behind you. Maybe its still regenerating when you pull up. Are you doing lots of short journeys?

 

[alfy1987]

You will get soot(ash) pumped out during a regeration, but normally you are driving so it should all be going behind you. Maybe its still regenerating when you pull up. Are you doing lots of short journeys?

Yes good point.
Journeys have been short, so perhaps it would benefit from a longer run. Although I couldn’t help but think the poor start the other day was linked in some way.

 

[Mooncat]

You will get soot(ash) pumped out during a regeration, but normally you are driving so it should all be going behind you. Maybe its still regenerating when you pull up. Are you doing lots of short journeys?

I'm pretty sure that the ash created during the regen stays within the dpf (this is the main reason these things eventually need to be replaced). If you have a properly functioning dpf, you can run your finger on the inside of the exhaust tailpipe and it will come out clean and is often how an MoT tester can see if someone has removed the dpf internals (black soot in the tailpipe).

I'm going with Loz's original diagnosis of brake dust.

 

[Loz]

I'm pretty sure that the ash created during the regen stays within the dpf (this is the main reason these things eventually need to be replaced). If you have a properly functioning dpf, you can run your finger on the inside of the exhaust tailpipe and it will come out clean and is often how an MoT tester can see if someone has removed the dpf internals (black soot in the tailpipe).

I'm going with Loz's original diagnosis of brake dust.

yes I agree, there should be visible soot as burn off is oxidised as per the vw SSP

Regeneration
The diesel particulate filter must be cleaned of the particles of carbon soot regularly to prevent it from becoming blocked and its function thereby being affected. During the regeneration phase, the particulates that have accumulated in the particulate filter are burnt off (oxidised). With regeneration of the catalytic coated particulate filter, passive regeneration and active regeneration are separated. There are no signs to the driver that regeneration is occurring.

 

[alfy1987]

Thanks all, really appreciate the help.
I’ll check the exhaust and see if there’s a build up. Otherwise I’ve seen other threads on re’ brake pads so will swap them out and see what the results are.

 

[Mooncat]

yes I agree, there should be visible soot as burn off is oxidised as per the vw SSP

Regeneration
The diesel particulate filter must be cleaned of the particles of carbon soot regularly to prevent it from becoming blocked and its function thereby being affected. During the regeneration phase, the particulates that have accumulated in the particulate filter are burnt off (oxidised). With regeneration of the catalytic coated particulate filter, passive regeneration and active regeneration are separated. There are no signs to the driver that regeneration is occurring.

I guess the SSP forgets to mention that the ash which is a by product of the regen is very slowly building up inside the dpf.