DPF Replacement

[wildtypitch]

Superb 1.6 TDI Greenline at around 140,000 miles and DPF analysis says 70g soot. Not safe to regenerate, Replace. Mostly city driving in the last two years. Warning lights on, performance limited. 

I'm looking for a replacement and official part 1600+VAT. I've found many aftermarket on ebay going for between £350 - 600. Sadly though it seems most are from Germany and can't guarantee they'll fit Right hand drive. 

This immensly handy website tells me the part number and indeed there is a right hand variant.  https://skoda.7zap.com/en/cz/superb/sup/2008-632/2/253-253063/?vin=undefined#1

So I'm in need of part 1K0 254 707 FX. They're available in Germany for ~EUR400 but too bulky to ship and UK routes seem to be all out of stock. 

If anyone has experience replacing theirs I'd love to hear from you. I did read on one aftermarket version that the left and right hand parts are interchangeable. Can anyone confirm?

I'd have thought this would be quite a common thing but I've not found much out.

 

 

[rover220]

Have it cleaned? 

[wildtypitch]

Is that a viable option? I heard that that'll just strip out and functioning element of the dpf.

What are the costs involved? I just presumed it was a very dodgy temporary solution.

 

[rover220]

These days I think its a genuinely viable option. 

[chimaera]

There are chemical processes that can remove the build-up from the filter. The remaining life will be lower than on a new filter but it's much cheaper than a replacement. Also, the part number you mention is a reconditioned exchange part (X at the end): you hand in your old one to be reconditioned and get a discount on the cost compared to a brand new part.

 

TBH if it's mainly soot build-up you could have avoided this as the car will warn you in plenty of time when the soot levels are getting high enough to be a problem. Oil ash is the silent killer of DPFs, soot build up comes with regular orange warning lights on the dash to remind you it'll die if you don't take it for a long drive soon.

[wildtypitch]

6 minutes ago, rover220 said:

These days I think its a genuinely viable option. 

Thanks I'll look into it.

Any North London recommendations?

[wildtypitch]

5 minutes ago, chimaera said:

There are chemical processes that can remove the build-up from the filter. The remaining life will be lower than on a new filter but it's much cheaper than a replacement. Also, the part number you mention is a reconditioned exchange part (X at the end): you hand in your old one to be reconditioned and get a discount on the cost compared to a brand new part.

 

TBH if it's mainly soot build-up you could have avoided this as the car will warn you in plenty of time when the soot levels are getting high enough to be a problem. Oil ash is the silent killer of DPFs, soot build up comes with regular orange warning lights on the dash to remind you it'll die if you don't take it for a long drive soon.

The feedback I got didn't stipulate soot or ash oil. I'm aware of the dpf warning light and it happened once before and quick run on the motorway cleared it. It happened this time but a few miles later I got the limited performance and more warnings.

[rover220]

At 140000 miles the dpf has done well. 

[langers2k]

I'd be wary that those figures are so different... Makes me wonder if a sensor has gone bad?

[wildtypitch]

56 minutes ago, langers2k said:

I'd be wary that those figures are so different... Makes me wonder if a sensor has gone bad?

What exactly are those figures? Is one ash and the other soot? Confused by the definitions calculated and measured.

[langers2k]

Both of those figures are soot.

- Calculated is a guesstimate at how much soot should be there based on fuel/engine use, last regen and a few other things

- Measured is based from the pressure across the DPF

 

It's not unusual for the two figures to be different but I've never seen them so different which is why I think it 'could' be a sensor that's failed.

 

I think the oil ash value (not shown) is based on how much soot has been burnt off. The oil ash cannot be burnt off which is why it normally determines the lifespan of a DPF.

[chimaera]

2 hours ago, langers2k said:

I'd be wary that those figures are so different... Makes me wonder if a sensor has gone bad?

Good point, especially since it's the measured value that's so high and that's driven by the sensor reading. A friend of mine with a Superb had the differential pressure sensor fail and it was constantly trying to regen. It did set a fault code though, which doesn't appear to be the case here.

 

The other thought I had on this overnight was the possibility of bad injectors rapidly increasing soot load above normal levels. I'd still have expected dashboard warnings at least once if not twice on the way up to such a high soot loading.

[wildtypitch]

10 minutes ago, chimaera said:

Good point, especially since it's the measured value that's so high and that's driven by the sensor reading. A friend of mine with a Superb had the differential pressure sensor fail and it was constantly trying to regen. It did set a fault code though, which doesn't appear to be the case here.

 

The other thought I had on this overnight was the possibility of bad injectors rapidly increasing soot load above normal levels. I'd still have expected dashboard warnings at least once if not twice on the way up to such a high soot loading.

Yes seems logical should have triggered regen at around ~25g soot measured. That fact that from dpf warning light to Glow light and limited performance was a few miles doesn't seems highly unlikely the cause is  ~50g of soot being created.

 

Just got off the phone from a DPF cleaning service which will remove the DPF and flush it in one of those specialist machine who seem confident that the pressure difference will be because of the ash oil and flushing it will bring it back to like new. £325 with 1 year guarantee.  Given the mile sunder the belt I think this'll be the most sensible option.   

 

 

[chimaera]

9 minutes ago, wildtypitch said:

Yes seems logical should have triggered regen at around ~25g soot measured. That fact that from dpf warning light to Glow light and limited performance was a few miles doesn't seems highly unlikely the cause is  ~50g of soot being created.

 

Just got off the phone from a DPF cleaning service which will remove the DPF and flush it in one of those specialist machine who seem confident that the pressure difference will be because of the ash oil and flushing it will bring it back to like new. £325 with 1 year guarantee.  Given the mile sunder the belt I think this'll be the most sensible option.   

 

 

The sensor is a lot cheaper than £325 so I'd suggest starting with replacing that. Cleaning out the DPF will make no difference if the sensor isn't working properly.

[wildtypitch]

4 minutes ago, chimaera said:

The sensor is a lot cheaper than £325 so I'd suggest starting with replacing that. Cleaning out the DPF will make no difference if the sensor isn't working properly.

Tricky, sensor £25, mechanic 1hr £80, VCDS adapted £60. Considering there's no warning lights  for the sensor... Maybe I'll suggest they try changing the sensor before the flush but don't really want to start telling them how to do their job.

[wildtypitch]

The sensor is really accessible so I took a multimeter to it and read a 1k ohm signal to ground which should be about right. If it was damaged it expect either a short, no circuit or a very high reading. It's no guarantee but makes me think it's less likely an electrical fault with the sensor. 

[chimaera]

If you can do it safely, it might be interesting to measure the sensor resistance when the engine is running. If the sensor is working the value should change while the engine is running. Or if you have VCDS, you can pull up the sensor readout in Advanced Measuring Blocks.

 

I've found issues where a sensor failed at a plausible signal level and never threw a code, but when its output was followed while the engine was running it was completely static when it should have been moving around.

Edited 22 September, 2020 by chimaera

[wildtypitch]

8 minutes ago, chimaera said:

If you can do it safely, it might be interesting to measure the sensor resistance when the engine is running. If the sensor is working the value should change while the engine is running. Or if you have VCDS, you can pull up the sensor readout in Advanced Measuring Blocks.

 

I've found issues where a sensor failed at a plausible signal level and never threw a code, but when its output was followed while the engine was running it was completely static when it should have been moving around.

Interesting, before I pull the trigger on the clean I'll use the VAG DPF app with the otgb II dongle arriving tomorrow to monitor levels. If it displays such detail.

 

[chimaera]

22 minutes ago, wildtypitch said:

Interesting, before I pull the trigger on the clean I'll use the VAG DPF app with the otgb II dongle arriving tomorrow to monitor levels. If it displays such detail.

 

You may need the paid version of the app but it does read out all information related to DPF operation and condition.

[wildtypitch]

1 minute ago, chimaera said:

You may need the paid version of the app but it does read out all information related to DPF operation and condition.

 Can't wait to see failure in actual numbers!

[WesH]

13 hours ago, rover220 said:

At 140000 miles the dpf has done well. 

Mine has 215000 miles never caused q problem.

[wildtypitch]

So got my little obd Plug and pulled some data below while revving the engine stationary. Oil Ash residue seems implausibly low. Any clues in that?

[wildtypitch]

Or a nice graph.

 

Things to note:

1. Differential Pressure is being recorded and in line with engine load.  Assumption: DPF Sensor working
2. Input gas Temp reading well but DPF Output gas temp Is stuck at 999. Seems like a sensor malfunction.  Assumption: If it can't read the output temp is can't engage the regen or control the temp.
3. High pressure EGR closing. Not sure what to make of this, it's constant 100%. Does that mean it's completely open or recirculating at max?

 

 

So based on this I'm considering replacing the sensor myself as it's very accessible. Or might I be reading the data wrong? I've disconnected the exhaust temp sensor and checked the obd and I indeed get P246F (Exhaust Gas temp Sensor circuit range/performance) error. Plug it back in and no P246F error jus the existing P2463 (Particulate Filter B1). Perhaps when it goes and reports 999 temp it's still considered within range?

 

[langers2k]

That does seem an implausible temperature

 

I don't know how your diagnostic kit labels the sensors but I know VCDS saw 4 temperature sensors on my CR140 although 'EGR temp 2' didn't seem to be fitted and always reported 0'C. The highest temperature I'd expect after the DPF is around 600-700 based on some old log data I have. If the sensor is cheap, I'd start by replacing that to see if the data is more plausible.

 

If so, you may still need to get the DPF cleaned but at least it (hopefully) won't block up immediately again.

[wildtypitch]

Sensor under £50. I'm also inclined to think that the ECU is reporting that 999 as a false number to shut down the DPF. Too convenient a number... Tried getting an ohm read on the sensor late last night but fiddly. Think I got a 1k reading but will need to do again properly. Could raise the temp and see if there's a difference while throttling. Think it's best I just take it to the DPF shop and let them figure it out.