Thread: Engine: B5254T2: - DFP Issues - what’s next...
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Old Oct 1st, 2020, 12:14   #4
Volvo XC90 T6 & XC90 D5

Last Online: Oct 8th, 2021 12:25
Join Date: Jul 2020
Location: Marple
Arrow Soooooooo...

So everyone,

After tracing the fault around the car from replacing the near knackered turbo, putting in the correct oil, replacing the PCV and Diff Pressure switch, checking the breething/vacuum system, replacing the near knackered intercooler to then write the car off on a rock (I then had to buy it back off the insurance company and I just installed a new sump for £50 quid + oil) I finally have News!!!!

I replaced the DPF today and instralled a new soot sensor and took it for a run - this is the results...

1) DPF pressure on hard acceleration dropped from 600+ to a normal 45 - 70
2) Car now drives amazingly!
3) Soot build-up was monitored on a 30 mile 40-minute leisurely drive (with occassional hard acceleration) and I parked up with 2.1% soot after the journey - some of this would probably be the engine cleaning itself from the "Asthma" its had for so long.
4) Oil level before I set off was at 75% and when I parked up it was at 77%
5) No smoke at all

So my assumption is that the previous turbo was failing (there was excessive play in the spindle once removed) and this was leaking oil into the dpf slowly killing it. The previous owner possibly put in the incorrect oil also. With the new turbo fitted the problem was solved except that the DPF was too blocked to properly regen. So the back pressure was pushing oil past the turbo seals and into the engine causing more soot in the DPF; I think this makes sense?

The car was smoking, not consistently, and I think it was only smoking as the car was trying to do a forced regen as the DPF was blocked and the smoke was the disel being injected and burning - hence the incostency.
When I tried to do a static regen it said the regen was successful except the Soot% jumped quickly back to 28%+ within a minute of driving or one blip on the accelerator pedal.

Lastly and most importantly, when free revving the engine, on RPM drop off there was a uuuuuugggggrrrrrrrr as the RPM slowed to idle. I think this was the key sign that the backpressure from the blocked DPF was causing the noise - worth listening out for on your cas as its now gone on mine with the DPF replaced.

I hope this helps others I didnt given up!!! Does it mak sense?

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