Hi Andy,
First I'd check the EGR to intake pipe for blockages as this is likley to be a choke point and the holes are quite small. As you now have a working EGR it may be possible that the restored EGR flow has pushed soot out of the cooler to cause a blockage. If you are going to clean the cooler I'd use brake cleaner and not DPF cleaner as likley DPF cleaner is designed to work with exhaust gases and heat. If it was mine I'd be very tempted to get the whole EGR system mapped out. 2012 TDV8 Vogue (L322)

I'm already one step ahead of you there. I've had the plenum off a few weekends ago to clean it properly, and did the EGR intake pipe and throttle body at the same time, sealing the throttle with high-density PTFE when refitting for a proper seal. By removing the plenum, I was able to access the EGR inlet pipe along with the electric motor, so removed those to access the valve and clean that too.

A year ago I was an EGR noob. I am now significantly better informed and practiced having taken it upon myself to learn things properly and to not be intimidated by the challenges. I've learnt that, if time is not a major issue, then there's not many jobs that can't be done on the driveway with careful prior planning and the right tools. That's why I'm not fazed by taking off the whole assembly for a proper clean if necessary. I could just do without the faff and additional costs if I can help, hence trying all this first.

The Vetech DPF cleaner I highlighted is designed to attack soot by soaking, it recommends 8-12 hours and the instructions are on the label in the photo if you're interested; it's got nothing to do with heat or exhaust gas. I am probably going to try option one (wet vacuum and brake cleaner) this afternoon and depending on results, consider option 2 and leave to soak overnight with the DPF cleaner before emptying the fluid and making sure none left before putting back together.

As for EGR ECM delete, I am tempted. However, the other long running thread on that exact topic for the 4.4 TDV8 hasn't yet convinced me. Ironically, when my ECM senses a problem and shuts off the valve, it's effectively an EGR delete as no exhaust gets past the valve or through the bypass when on throttle, and it's only when off throttle that the bypass valve opens to allow the system to not overpressure I guess. It's easy to observe this on the Gap tool. The benefit is that, far less exhaust is going through my engine and my fuel economy noticeably improves. What's not to like? However, I can't imagine it's healthy to ignore the issue and run it indefinitely as it will just cause problems elsewhere over time and probably with the DPF again. When you do the EGR delete, it physically blocks off the EGR yet I can see that the EGR plays a part during regeneration. The valve remains closed and bypass is open so no gases get cooled, helping the DPF get to temp. However, when you come off the throttle the bypass closes and valve opens fully, which I presume is some kind of failsafe. My worry is that the tuners I spoke to recently at the LR Show in Malvern (Alive and Emporium) said you need to delete the DPF also. In layman's terms, the DPF gets physically gutted to remove the monolith. Seeing as I just paid £2400 for a new one, and there is a real prospect of particulate measurements being introduced to MOTs in the next few years, I'm not willing to do a DPF delete and then have to put another new one back on. Also, like you, I think the emissions laws are positive on balance so don't want to tamper with a system that benefits all of us, even if it does cause the odd problem if the system is not cleaned and maintained. Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Sounds like a plan and good luck with it. My EGR cooler is weeping coolant but it's a pig of a job to change so I've opted to just top up the coolant every so often rather than paying >£2k to have it fixed. 2012 TDV8 Vogue (L322)

Good news on the cleaning front (I hope). I’m not finished yet as awaiting some new gaskets for the EGR pipes before I put it back together and hoping they get delivered tomorrow. However, the wet vacuum worked a treat!

I started off doing it with brake cleaner, and put a whole can through with the cooler bypass closed to make sure all the cleaner gets sucked through the cooler. However, it’s hard to determine how much came out as the brake cleaner evaporates so quickly. I then tried it with the DPF cleaner fluid, but instead of pouring it in I used a pressure sprayer with a length of pvc tube to get it into the intake. I sprayed 1L in and managed to get 1L out into the wet vacuum. When it came out it was very very black, so it’s definitely dissolved a load of soot when going through the cooler.

Anyway, once the gaskets arrive I can get the plenum back on and get it fired up to test whether it’s done what I’d hoped and cleared any restrictions in the cooler. I’ll be able to tell quite quickly by monitoring the EGR values on a decent run.

Fingers crossed this works as, it was a surprisingly easy thing to attempt and I hope warrants a how-to. I know how much people speak about dirty plenums and how gunked up they and the air intake manifold ports get. That gunk comes from somewhere and it all goes through the EGR valve and cooler. So, if the plenum suffers then the valve and cooler must also. As such, doing this every few years as a bit of preventative wouldn’t do any harm at all seeing how easy it is to do!

Not sure when gaskets will show but hoping ASAP as can’t wait to see how it drives. If it’s not fixed my P0401 then back to the drawing board but, I’m pretty optimistic. Fingers crossed 🤞 Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Just a wild idea reading this post:
If you're sure the cooler is sealed enough you could attach hoses on both ends, tie them up on a higher point and fill the cooler up with the DPF cleaner and let it sit & soak overnight?
Even wilder idea:
Create a closed loop with tubes and a tank and use a 12V fuel pump to pump the cleaner around for a while? 2012 4.4TDV8
2000 Honda S2000

SpitfireS, this is not a wild idea at all and was the genesis for my thinking/planning when doing this. I’m aware of companies like Terraclean that promise miracle cures but it’s just snake oil as at no point do they do anything that gets direct contact with the areas or concern; it’s always a secondary effect such as after combustion.

The pain in the A design of the 4.4TDV8 EGR system for when it comes to removal is actually a blessing for this type of cleaning as, the body which contains the cooler and valves is the lowest point in the sealed system. The exit pipe is really high and easy to access. And the inlet port is open and faces vertically up, plus is also higher than the main body.

Therefore, your first idea of literally filling it up with fluid is entirely possible with no risk of spills. It’s just physics as long as the car is level. If the EGR valve is held open, when you see fluid filling up through into the inlet port you’d have certainty that the cooler has been flooded. If in doubt, just actuate the cooler bypass valve by hand to be sure fluid gets into the cooler. As for the seals, it’s a closed system that relies on pressure to close the throttle and not stall, so whilst it could weep a very small amount of fluid if the gasket wasn’t a perfect seal, it can’t leak or the system wouldn’t operate.

As for your second idea, I also considered the same but that’s more challenging. One, you wouldn’t want to recirculate dirty fluid on a continuous loop, so it might require a lot of fluid or a very very good filtering method. Two, the inlet port is square so it would be difficult to achieve a good seal and the easiest solution would require modification of a spare inlet pipe and connecting into the circular entry to the cast iron section; i.e. take off hose clip and sock, then chop off the bendy bit to make an adapter.

Update.

I put the car back together today after new gaskets finally arrived. It started first time and no issues in first few minutes with engine running. I held revs at about 2k for a minute to ensure a good flow of air through the intake manifold in case anything got blown out of EGR and into cylinders. All was fine. There was no reason this shouldn’t have been the case but good to play it safe.

I went for a drive and monitored the EGR valve commanded value, EGR valve position, EGR cooler bypass valve position and throttle position. I drove for about 35 miles, the last half mainly dual carriageway cruising so perfect conditions for the EGR valve to open to max (which is the point that it was shutting off before). I am very pleased to report that at no point did the valve shut down which was a symptom I was consistently observing. I am also 99.9% confident that prior to my EGR valve and cooler clean, the valve would have shut off under the described driving conditions.

This is only one drive so I am not going to be so bold as to say that my P0401 error has been fixed. I will keep monitoring the EGR values over the coming week and I have a few good long drives on which to do this to be sure. However, I am quietly confident that this has done the trick and, if a success, I’ll do a proper write-up with pics as a ‘how to’ should others wish to do this procedure on their vehicles. It’s a damn sight easier than trying to do this off the vehicle, and is a surprisingly easy and simple procedure to do. It just takes a little leap of faith in basic physics.

Anyway, fingers crossed for me, no more EGR shut downs and no more P0401 and MIL light coming on! 🤞 Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Would you, Ajmngn, say it's possible to clean the EGR the way you did but without the fluid vacuum cleaner?
Or is it necessary to make sure you get ALL the fluid out of the EGR?
Is the DPF fluid you used very volatile?
Would it be enough to let the EGR ventilate for 24hrs for example to remove any fluid?
 2012 4.4TDV8
2000 Honda S2000

Great write up. Just my 2p - if I had the DPF diagnosed as needing replacement then I'd have gone straight to Empire Tuning in Colchester and had the DPF and EGR "sorted"
I've researched various companies that can do this "just in case" and they keep coming back...
Thought I'd add this for others reading this in the future Gone to a good home: 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
2025MY Defender D350 90 in Silicon Silver on coils
1974 Series 3 Lightweight = "Millie"
Many, many other Landies over the years
My preferred specialist: www.glenrands.co.uk
--------------------------------------------------

All good and well currently, but the MOT Test will be bring in PM testing at some point (already undergoing trials in selected stations)

In the long term, that may prove to be a very costly "fix"

https://www.endsreport.com/article/1810762...provements

Noted  Gone to a good home: 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
2025MY Defender D350 90 in Silicon Silver on coils
1974 Series 3 Lightweight = "Millie"
Many, many other Landies over the years
My preferred specialist: www.glenrands.co.uk
--------------------------------------------------

SpitfireS - the fluid I used works by dissolving carbon so deposits become suspended in the liquid. Therefore, if you put the fluid in then it needs to come out somehow, and I’d suggest measuring volumes before and after so you can gauge how much may remain before attempting to restart the engine. The risk of hydrolocking the engine is real, so it is imperative to remove the bulk of the liquid. I was initially just going to flood the EGR valve and cooler assembly and leave overnight. That would be the optimal solution. However, I elected to learn by doing and take it easy at first, so I chose to spray it through the EGR assembly instead. The logic was that an incremental approach would be better, as I could always use the flooding method as a next step if spraying didn’t work. I’m optimistic I won’t need to do that now but am confident I could if needed. The wet vacuum was the thing that made it a sensible endeavour as the suction achieved through the EGR assembly was excellent. You could try other options instead of a vacuum, but I can’t think of a more practical or easier way to be sure what went in came out. I would also ward against thinking you could get a hose down the outlet sufficiently to draw the fluid out using something else, like a suction pump. I struggled to get my endoscope past the EGR temp sensor on the outlet pipe and didn’t want to damage that by trying to find a way past. The sensor is only half way down the pipe to the valve gallery and you would need a hose to get right down into the gallery to get the fluid out sufficiently. 👍

Dr Rob - I agree EGR and DPF delete are one approach to deal with a common problem, but they also come with risk so, before recommending those options, a balanced view is important. An EGR delete in the ECU is relatively simple as, in theory, a cleaner engine is more efficient and thus could still meet legislated emissions regs with the delete in place. I’m sure you’re well aware, but UK law does not say you can’t delete EGRs, it only says that you can’t modify the car such that it does not comply with the regulated emission levels. Also, EGRs only fully open when at a steady cruise so, they are kind of pointless in the urban environments where air pollution is a big issue, as they either only open partially or not at all at low speeds or idle. During an MOT, it is hard for a tester to determine if an EGR valve is open partially, fully, or not at all, even if holding revs. It would at least require OBD2 readings to be monitored. This makes measurement of emissions difficult if seeking consistency when applying a standard. Additionally, there’s no such thing as a DPF delete just in the ECU. What actually happens is that the DPF is gutted and the filter’s monolith is physically removed. There’s no other way to do it as, if you switch off the DPF system in the ECU, particulate matter (PM) is still captured by the filter and will never regenerate to clear itself. Removing the monolith means no PM is captured at all and it therefore invariably won’t meet the requirements as stated in law. Euro 4 levels were 0.025g/km of PM. Euro 5 and the introduction of DPFs reduced this to 0.005g/km of PM for diesels, and DPFs capture 99% of a diesel car’s PM (https://www.rac.co.uk/drive/advice/emissions/euro-emissions-standards/).

Also, see here relating to DPFs

Click image to enlarge

Update 2

The symptom is back! 😵‍💫😂😂😂 I did a nice hours drive each-way last night and, at the back end of my outbound journey, the EGR’s ‘commanded position’ and ‘valve position’ values were fully open and then it shut itself off. FFS!

On the way back, it barely lasted 5 mins on the motorway before shutting down again. There’s no fault code yet as it takes at least 3 consecutive logged occurrences for it to trigger the DTC and switch on the engine’s MIL light in the dash, but I’m certain it will be the same P0401 as everything happened the same as before attempted cleaning.

My thoughts:
1. The behaviour of the EGR valve after the attempted clean on the vehicle has been fundamentally different to what I’d observed previously, in that it was operating normally and fully open on my 45 mil test drive. That wouldn’t have happened before. Furthermore, it took about 35 mil last night before it did then finally give up. Therefore, whatever I did must have improved the situation, but not enough to stop the symptom reoccurring.
2. I only put aerosol and pressurised liquid through the EGR cooler, and that was under significant vacuum suction. On reflection, I doubt the brake cleaner had a chance to do much before evaporating. As for the DPF cleaning fluid, that would’ve just got sucked through very quickly by the vacuum without having much time to attack the carbon; but it did do something as it came out very black indeed! Therefore, the liquid needs to be in contact with any carbon much longer to have a chance of breaking it down and dissolving any deposits that might be in the cooler.

My only other option now, without removing the assembly for cleaning, or deleting the EGR from the ECU, is to do what I’d suggested all along and flood the cooler and leave to act overnight.

Some of you think I’m mad, but I’m pretty certain that I know what I’m doing. Wish me luck! 🤞😂

 Andy

2010 4.4TDV8 Vogue SE in Santorini Black with Ivory interior
2017 Audi SQ5 3.0 V6T Quattro in Volcano Red
2001 Audi Allroad 2.5 TDI manual with low-range in Highland Green. Currently SORN whilst undergoing some serious restoration!

Not sure what chemicals actually ‘dissolve’ carbon. If it’s blocked with the kind of the stuff found in the intake it will take something more aggressive than a soak and flush. Also there is a possibility it’s not blocked and it’s a sensor error. 2012 TDV8 Vogue (L322)

Hello Ajmngn, I'm sorry to hear the code came back.

Browsing the web I found this image of a blocked EGR end tank cooler.
It was described as a 2011 4.4 TDV8 EGR.


If yours looks anything like that I'm thinking soaking would not do much.

Maybe you have to take the expensive plunge and have it removed.
 2012 4.4TDV8
2000 Honda S2000