DPF plugged and advice needed

[The Good Shag]

Had to get a new DPF at £520 + VAT plus more bit plus labour.  £924 all in.

After my car had lain for 2 weeks I got about 3 miles then put the foot down as I hit a dual carriageway then there was a bang.  No lights, warnings, buzzers or anything.  The car lost power and it sounded like the exhaust had gone from the noise.  Limped along for 3 miles and it eventually cut out completely and I had to get recovered.  The bang was caused by the intercooler hose blowing off due to high pressure caused by a blocked DPF.  Now I know that regeneration is supposed to take place automatically and obviously this hadn't been happening.  The guy in the garage showed me the old DPF and it had about 10mm of soot built up on the inlet side.  I topped up the fluid about a year ago with stuff I got on Ebay.  No it wasn't Adblue but the stuff they use in Volvos and Peugots and it seemed to be the same spec.  So my question is...........was it the wrong fluid or is there perhaps something wrong with the differential pressure sensor which is supposed to detect when a regen is required.  If it is the sensor, is there any way I can check the differential pressure using VAGCOM which I have.  What are the memory addresses for this differential pressure sensor.  I don't want my new DPF going the same way because the regen process isn't happening as it should.  I am after informed advice.  Please don't tell me to get rid of the car as this isn't an option right now.

[BJM]

WRONG FLUID

It isn't AdBlue which is designed to react with the exhaust gas to reduce NOx. Emissions. AdBlue does nothing at all for carbon ash removal.

it's a special fluid, only obtainable from VAG dealers at around £45 a litre.

Search the forum there are several threads about it.

[jimbof]

Easy tiger - I think he said it wasn't adblue he was using...!  Though it would be useful to know exactly what the fluid was... 

I've linked before to the VW self study guide on the DPF system fitted to these cars but here it is in case it is useful to you:

http://www.volkspage.net/technik/ssp/ssp/SSP_330.pdf

 

I'm not sure about the pressure sensor idea - I thought that the readings these should report vary over the engine rev range, and if that isn't happening you would have a fault of some sort.  Hence why on the Peugeot systems at least a remap is required to map out the DPF - there isn't just one value of resistor etc that you could wire in instead of the sensor to "fake it".  (see the section "Flow resistance of particulate filter", and also "The sensors

Exhaust gas pressure sensor 1 G450")

 

Do you know the history of the car?  Isn't it more likely that it was coked up just from being run without fluid for too long by a previous owner?  Once they coke up to a certain point the regen can't clear it.

 

I'm not a mechanic, just thinking aloud here  anyway hope the info / ideas are useful.

Edited 19 March, 2014 by jimbof

[The Good Shag]

The fluid I used was like this

http://www.ebay.co.uk/itm/GENUINE-VOLVO-ADM-FLUID-ADDITIVE-KIT-EOLYS-1161752-DPF-OIL-/111301591006?pt=UK_Vehicle_Oils_Lubricants_Fluids&hash=item19ea177fde

 

I've had the car since 30,000 miles and have never had any trouble with it other than a radiator leak which was replaced under guarantee.  I read the self study guide before I bought the fluid and was convinced it was the right stuff with the right iron content.

 

Since getting the car back, I've has an emissions warning come on and VAGCOM reports

 

18366 - Exhaust Gas Temp Sensor 2 Bank 1 (G448)
            P1958 - 000 - Short to Plus
             Freeze Frame:
                    RPM: 0 /min
                    Torque: 0.0 Nm
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Voltage: 12.92 V
                    Mileage: 60 km
                    Temperature: 138.0°C
                    Absolute Pres.: 979.2 mbar

 

It wasn't on when I got the car back and I reset it only for it to come back on a couple of days later.  The guy in the garage says that the sensor may have been sooted up too and it should burn off after being run for a bit.  If it doesn't I shall be taking it back.  Is this sensor prone to failure?  Anyone know?

[jimbof]

No idea to your question; out of interest do you do much stop-start driving?  Or do you know how it was driven during the first 30,000?  I would guess that it was actually coked up because of driving style or journey profile.  This is very common on the similar built Peugeot DPF systems of a similar age - and if you see the self-study guide these DPF systems really cannot deal with that sort of journey.

 

I kid you not; the regen on Peugeot 307's around 2004 is so marginally good enough even under optimal conditions that they turn on the heated rear window demister during regen to try and put a tiny bit extra load on the alternator to in turn load the engine to get the exhaust temperature up...!

[The Good Shag]

Most of my driving is high speed motorway stuff.