Technical [263] Why is my DPF differential pressure so high after a reverse flush ?

[clayts450]

I'm still having DPF issues.

Work done so far:

• 17 January 2025 Replacement turbo at 78913 miles (Lindleys)
• 17 January 2025 Oil change, new filter, correct oil Castrol Magnatec 0w30/C2 at 78913 (Lindleys)
• 27 January 2025 Fuel filter changed, front brake discs/pads changed, replaced differential pressure sensor and recalibrated (self)
• 28 January 2025 MOT at 78991 miles – evidence of slight oil leak noted (VTS)
• 21 February 2025 Replacement high pressure fuel pump at 79055 miles; diagnosed new turbo faulty, also two injectors out of tolerance (Gee Diesel)
• 28 February 2025 Replacement turbo fitted (under warranty), also observed oil leak and advised they had ‘tightened a pipe’ before turbo was replaced (Lindleys)
• 28 March 2025 Oil leak observed at front of engine, dripping onto pipe between DPF and low pressure EGR heat exchanger: identified turbo oil feed pipe had failed – replaced (VTS)
• 07 May 2025 DPF analysis (pass - good DPF no damage, 75% soot blockage - MES read about 50%), removed, cleaned in CC25 machine and dried, refitted, road test all okay)
• 12 May 2025 Road test - see FES attachment (done in the style of the Ducato data gathering exercise, per @theoneandonly

DPF observations:

• 30 January 2025 Heavy smoke from front of engine after an active DPF regeneration whilst at 20mph, cause unknown at that stage – thought to be due to oil leak. DPF regeneration reduces % clogging to 13% very quickly (default lowest percentage), but continues to attempt to regenerate – up to 25 mins (normally 10 minutes max).
• 31 March 2025 Active DPF regeneration again took too long – smoke observed coming from behind the heat shield at the bottom of the DPF adjacent to pipe to low pressure EGR heat exchanger.
• 04 April 2025 Differential pressure increased rapidly during fast journey from Loughborough to Kendal, high revs (over 2500) seems to result in DPF pressure increasing very quickly, soon reading over 300mBar. Ultimately two codes were thrown (see below), P1206-22 and P2002-22, even though %clogging was around 30%. Limp mode (no revs above 3000) for 300 miles approx.. Had used 1 litre of engine oil when checked next day (from max to min on dipstick). Cleared codes. DPF clogging percentage at 105%. Low MPG.
• 06 April 2025 Refuel. Took for drive – differential pressure was low enough (below 200 mBar) that active regeneration started. Again, dropped to 13% clogging after 10 minutes (M1 between 2500-3000rpm), but continued to regenerate for 25 minutes. Driving for most of this time. Resulted again in smoke coming from behind heat shield at the bottom of the DPF next to the pipe to low pressure EGR heat exchanger. No codes shown. Added Archoil AR6400D Max to fuel tank.
• 12 April 2025 Took for drive, clogging percentage was at 30%. On M1 between 2500-3000rpm, the clogging bizarrely shot up from 30% to 125%, and a regen started. Usual story – reduced to 13% quickly, then process continued for 25 minutes (driving for most of this time), smoke again from the same place as 06 April 2025. No codes shown.
• 13 April 2025 DPF clean – 1/2 litre of Wynn’s off car DPF clean under pressure (garden sprayer) through DPF pressure sensor tube, engine off. Then a further 1.5 litres with engine at idle. Foam very quickly appeared at backbox. Also observed foam coming out of the same area as the smoke has been coming from (behind heat shield at bottom of DPF next to pipe to low pressure EGR heat exchanger). Let sit for 45 minutes, pressure reduced. Took for drive – any remaining fluid was evaporated. Took onto M1 – differential pressure quickly up to 200mBar at 2500-300 rpm. Sitting at 25 mBar at idle and 105 mBar at 3000 rpm when parked up after journey. Still the same now.

Freeze data for error messages 04 April 2025:

In spite of the work done, and with a supposedly clean DPF I'm still getting high differential pressure readings (or what the YouTube DPF King Jimmy O'Riley would say is within scope - ideally up to 10mBar idle, 50mb at 3000rpm).

No EMLs since the work was done.

Anyone able to dissect and advise why I may be having such high pressure readings (40Mbar idle after a 28 mile, 30 minute drive on M1, 83% clogging) ?

Thanks for your help.

 

[Greasytrucker]

Is it not possible it’s started to break down so effectively the honeycomb shape, or part of it isn’t as it should be hence quickly clogging again. Only takes a clatter at some point to damage it. They do get past the point of cleaning sometimes

 

[clayts450]

Is it not possible it’s started to break down so effectively the honeycomb shape, or part of it isn’t as it should be hence quickly clogging again. Only takes a clatter at some point to damage it. They do get past the point of cleaning sometimes

Good theory, and indeed something I mentioned myself when presenting the van at the last garage. They use a clever device which analyses the condition of the DPF and provides a 'filter efficiency value' - mine passed with flying colours, aside from the obvious blockage. If there had been damage I would hope it would have been picked up.

 

[Greasytrucker]

Good theory, and indeed something I mentioned myself when presenting the van at the last garage. They use a clever device which analyses the condition of the DPF and provides a 'filter efficiency value' - mine passed with flying colours, aside from the obvious blockage. If there had been damage I would hope it would have been picked up.

Yes you’d hope

 

[clayts450]

Interesting development today - did it's first regen after the reverse flush, didn't wait until blockage was over 100% (as it used to), it was 89% but pressure was high (around about 350mB at 60-65mph 2500-3000rpm - this always used to trigger an engine management light).

Also completed the regen in 10 minutes (usual reduction to 13% blocked) then stopped, which is a huge improvement on what used to happen (it would keep going for 25 minutes, essentially until it timed out). Pressures also dropped significantly.

I think I may have been worrying unnecessarily - at least at the moment it seems to be doing things right. Fingers crossed it stays that way. The proof in the pudding will come when pressures maybe increase and the % clogged is low, as this always seemed to be when it threw up an EML. Although, TBF, I ran it from 59% to 89% clogged with high differential pressures (even hit over 400 mBar yesterday) and it was as good as gold.

TL: DR Don't mess about with foam cleaners or other cleaners that promise the moon on a stick. Pay to get the DPF taken off and backflushed. The van feels as perky as it has ever done in my ownership, and positively flies again.

 

[Greasytrucker]

Interesting development today - did it's first regen after the reverse flush, didn't wait until blockage was over 100% (as it used to), it was 89% but pressure was high (around about 350mB at 60-65mph 2500-3000rpm - this always used to trigger an engine management light).

Also completed the regen in 10 minutes (usual reduction to 13% blocked) then stopped, which is a huge improvement on what used to happen (it would keep going for 25 minutes, essentially until it timed out). Pressures also dropped significantly.

I think I may have been worrying unnecessarily - at least at the moment it seems to be doing things right. Fingers crossed it stays that way. The proof in the pudding will come when pressures maybe increase and the % clogged is low, as this always seemed to be when it threw up an EML. Although, TBF, I ran it from 59% to 89% clogged with high differential pressures (even hit over 400 mBar yesterday) and it was as good as gold.

TL: DR Don't mess about with foam cleaners or other cleaners that promise the moon on a stick. Pay to get the DPF taken off and backflushed. The van feels as perky as it has ever done in my ownership, and positively flies again.

Good news, hope it continues