The Great DPF Debate - The correct answer at last!

Cabernet02 · April 21, 2022

So this post is aimed at trying to get you all on the straight and narrow road to fix your DPF issues once and for all. This is not a call for help because I have cured the problem myself.

I will try to compress the last 9months experience into quick readable piece of information which you should all take on board now or keep for the future when the dreaded ‘RP’ makes an appearance.

I must also state my car is a Jaguar S-Type 2.7D 2007 SE with 77K on the clock.

Having been through the mill reading more stuff about DPFs and the reasons the ‘Restricted Performance’ light is lit and the so called cures for this ailment – some of which you will realise are a total waste of your time and most of all – your hard earned money…

Right – Are you sitting comfortably – Then I shall begin… (Showing my age there)

In August 2021 I decided to buy my second S-Type as it had less than a third of the mileage of my original car which I’d owned for 8years – Hind sight – I wish I had kept my old girl –sometimes the grass is most definitely not greener!

I did all the things guys do when they buy a new car – Oil & filter Change - upgrade the HiFi – Thoroughly clean the Leather – polish the paintwork – check as much as possible under the bonnet – check all the pads – replace the Air filter – Fuel filter – Wipers – Millers to the Diesel etc.,etc.

The car performed great for the first 2 months… but then the dreaded ‘Restricted Performance’ came up. Having had some experience with the previous 2.7D Sport, I was well aware of what was required or at least I thought I was.

This is the opening of the worm hole that leads most of us on the infamous ‘Bum Steer’ that can lead to so much despair. You see if you actually take a step back and consider what you think or have been told to do by some of the many many posts you have read, you will NOT enter!

The previous car that had nearly EVERTHING replaced that leads to the ‘RP’ scenario – Turbos - EGRS – MAF Sensors – MAP sensor – Smoke Test to Inlet Manifolds – Throttle Body Cleaned – Timing Belt – Water Pump etc., you just carried on as normal and the light would go off after your next jaunt up the motorway – all good. Some of that in part due to the excellent previous owners servicing.

This car however decided it was not going to play the game – and ‘RP’ was here to stay. It would come on as soon as I left the driveway. This baffled me to start with as it does not come on when parked, I assume it interacts with the ECM and ABS sensor, anyway – not important.

First – Several 30min runs on the motorway above 2000rpm and the light would go out for a day or two – then make a return like a long lost friend. Not long after the ‘RP’ would bring one his mates to the party - the RED light also came up.

OK digging deeper – Checked intercooler Pipe but it was like new so must have been replaced previously. Checked both rubber / silicone pipes from the DPF to the Differential Pressure Sensor, both like new – Checked the Inlet manifolds for leaks – all good. Checked the differential Pressure switch by removing the larger bore Rear Pipe which is the front of the DPF – short drive and the warning lights are off and stay off for some distance which means the DPF is blocked and needs cleaning.

Time for cleaning – lots of ‘On Car’ DPF cleaning companies out there – “no need to dismantle your exhaust – we will clean it on your driveway or at work”… Great stuff…£150.00

They came – they supposedly cleaned it and ran the car at 2500RPM while parked and with what looks like a modified garden spray green fly killer lance injected their cleaning fluid into the system somewhere – I have no idea where to this day? “Look” he said “the exhausts are blowing much better out the back than before”. Yes I said like an idiot as I have never seen the exhausts running at 2500rpm as I am usually in the driver’s seat! (Insert emoji with surprised look & no mouth).

An accompanied drive with the guy and his computer attached we went for a jaunt up the motorway and all was good for the usual mile or two then the light came on again. He said “it’s your differential sensor, it will be faulty and needs to be replaced. OK next day – off to JAG and purchased the replacement £95.00 – Fitted on the way home and light came on – the friend you wish you had never met.

More blasts up the motorway – nothing.

Purchased an Icarsoft scanner tool £150.00 and checked the fault codes. Everything the posts tell you and more – my Sat Nav voice guidance was missing something – again not important!

Anyway stick to the story, ‘Differential Pressure sensor High’ etc etc… Time for a forced Regen via the tool. Wow it actually worked and the tool told you how much was left in the DPF, Happy days.

3 Days later ‘RP’ was back with his mate Mr Red.

Time for a dramatic move – replace the DPF – there are a couple of companies in the UK who make these things and all with good reviews so let’s get this sorted once and for all I thought and start with a new datum.

DPF Plus new pressure sensor feed pipes £200.00 approx., from CATSRU or DPFtoU or some such company, much cheaper than JAG. I fitted it and cleared the faults & carried out the install/register of new DPF on the scan tool. 0.0G and pressure sensor correct. Got another Oil & filter change done £120.00 as we all know that’s important. The only big downside was I was not able to park the car on the drive way as it’s quite a camber up the pavement to our drive and the new DPF sits about 50mm lower than the original and with four people in the car over sleeping policemen - it scrapes so it had to be parked on the street- sad face emoji!

System all good for what I remember to be 6 weeks then guess who came back to make an appearance? You’re ahead of me - I can tell and you’re right of course... ‘RP’ and Mr Red. I was shocked I can tell you.

What to do now? Go deep as it must be something upstream creating all this soot to block a Brand New DPF? Checked the turbo actuators, Swirl Valve Actuators, EGRs are clean and cycling perfectly, Connecting Pipes, Cleaned All MAF & Map sensors, rechecked Inlet Manifolds, Cleaned throttle body though it wasn’t really dirty, checked wiring to DPF sensor.

Off up the motorway and managed a regen and lights out for a couple of days before they came back. I was now very worried that the rings are badly worn or injectors are faulty – or – or?

My fear was I would suffer the Diesel Engine Runaway death and that would be the end…

You know when you sleep on things and you get that lightbulb moment, well that’s what happened.

I still had the original JAG DPF and I was going to get it cleaned properly without cutting it open or hitting it with a pressure washer or removing the core. I researched it carefully and found a company in Manchester who clean the DPF off car / lorry in a purpose made high pressure system using specialised chemicals. £125.00. Exciting – I know – I could hardly contain myself.

I dropped it off and collected the next day and was given a printout of the exhaust performance in the specialised machine. In short the machine produced a before and after result so you understand how good the clean result is.

The guy (sorry don’t remember his name) showed me the machine and demonstrated the air pressure test, the air hose is about 50mm diameter and showed a reading to atmosphere of 1.19 (unsure of units used sorry). The air was seriously blowing from the flexible hose and he then tried to cover the end with his hand and could only get it to about 1.4.

Pre clean the Air pressure system reported back 1.70 – that was one of the worst he had ever seen he was surprised the car ran at all.

After Cleaning it read 1.19 so definitely clean. Had the cleaned original exhaust fitted back to the car £95.00. Reset the ECM with the scan to for the now Like New DPF and cleared all fault codes then had another Oil & Filter Change £110.00. A point to note here also is they clean the rubbish from the DPF out from the input side which is absolutely logical. Also if you take a minute to think about it all the ash will just accumulate and needs to leave from the way it came in. there is no longevity in On The Car cleaning – Ever.

That was December 2021 – car has been running like a dream since the ‘RP’ & his mate MR Red are dead, RIP. Better than that, on a god run the average MPG just climbs and climbs. A recent trip to York I was nearly at 40mpg which is brilliant.

It also turned out the car was sort of running with a blocked DPF as it had blown one of the flex joints before the CAT which was another £300 to have it replaced due to broken stud on the turbo connection.

Epilogue:

“If your diesel car is showing the ‘RP’ Light and she has done over 70K – Do Not get the ‘On The Car’ cleaning people to work on it, you are just kicking the can down the street. They cannot clean it properly and the light will return. A proper Off Car cleaning machine (not a Karcher pressure washer) will wash the soot out from the end it came in and remove all the ash. This is the gospel according to me and I wish I could have found this information from the beginning and saved… how much!!!

£1295.00!! OUCH!!! Yes – that’s what this exercise cost me but still have the scanner tool which has helped me cure the Sat Nav issue which turned out to be a closing loop for the optical network £5.00 eBay.

So if you have money to burn, off you go, you crack on - but believe me if it’s blocked it’s blocked – the end. Get it to a professional company who remove it and flush it properly.

There are many reasons the genuine JAGUAR DPF is so expensive, the build quality is far superior, the body of the DPF is much bigger than the aftermarket unit that frankly looks like a baked bean can compared to the size of the original - ergo surface area is less thus less capacity. The materials are inferior and it hangs too low. I also have noticed that the aftermarket one is rusting up nicely in my yard like some kind of Angel of the North statue which also tells me the grade of stainless is rubbish. The original one did not rust off the car while I spent ‘Loads of Dosh’.

I can also park the car back on the drive and I now have that smug Jaaaaag face when washing my car and polishing my leaper. Nice.

I hope you enjoyed this journey and that it was worth getting to the end like any good read and armed with this knowledge you go forth and make the right decision and save yourselves a huge amount of the folding stuff.