Are vehicles with these things fitted to be avoided and if so why ?

Well all diesels have had them for a number of years... just something else to go wrong... or buy a petrol....  Pete

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Not so good on town only cars!!!

DPFs have been known to be quite problematic

A healthy filter should look similar to this

Click image to enlarge

Click image to enlarge

@ buy a petrol


Ok thanks, why do people complain about them ?

Are the expensive to replace / do they hinder performance ?

Is it Illegal to remove them / interfere with them ?

As above.

The issue is that to regenerate the DPF (burn off the soot clogged in it to clear it) the engine needs to reach certain operating conditions (the DPF needs to get very hot). This entails driving at a constant slightly higher rpm for a certain amount of time (around 10 to 15 minutes) in order to produce the exhaust heat required. If you regularly cruise on a motorway/dual carriageway at the legal limit then it should cause no problem. The trouble comes if you always use your vehicle in stop/start town driving conditions and never reach the burn off criteria. Eventually the DPF will become clogged and you will get an error light.
The regen cycle can be forced by diagnostic equipment but it will still need to be sat running at higher rpms to clear it.
If that doesn't clear it then you can try fuel additives or you need to get hands on. If that doesn't work then it'll need replacing. Using better quality fuels, the correct engine oil and taking it on a motorway run every so often will help the situation by not letting the DPF getting clogged so easily.

The other issue, although not with current LR diesel engines, is some engines use a slightly different DPF system. LR places their DPF close to the engine to get the necessary heat for DPF regen. If the DPF is further down the system so can't get as hot as easily then to burn off the soot a chemical is injected (Urea or other) to help the burn off regen process. This means ever so often you need to replace or top up this chemical and another bit of kit that might fail (pump etc.). That is also another expense come service time although typically it should last about 60k miles.

As you can see due to the extra servicing expense and possible expensive to fix problems it was quite popular to actually delete the DPF from the system although illegal to do so. To prevent that the DPF was added to the MOT test, if a vehicle was fitted with a DPF from the factory it must physically still have one come MOT time (the same as the CAT). Whether they know what's actually inside the DPF shell is another matter!

The solution, as Haylands says, buy a petrol!

With regard to cost. My Skoda Superb needed a replacement (only 3 years old ,just out of warranty) It was about £1,600

Weejock wrote:

As above.


As you can see due to the extra servicing expense and possible expensive to fix problems it was quite popular to actually delete the DPF from the system although illegal to do so. To prevent that the DPF was added to the MOT test, if a vehicle was fitted with a DPF from the factory it must physically still have one come MOT time (the same as the CAT). Whether they know what's actually inside the DPF shell is another matter!

The solution, as Haylands says, buy a petrol!

My current car (not LR), went for its first MOT under my ownership in Feb. The car passed but was told by the garage that the DPF box had been repaired (weld patch). He suspected that the DPF may have been 'modified' but can only pass or fail the car based on actual emissions, as these were 0.00 it passed.

I have never needed to regenerate the DPF on my car but my wife's Jag needs a little 10 min run every 10-12 months and all is fine.
Just the incompetent government/s not knowing what there talking about, again

Just like leaded v unleaded. Cat's v lean burn. Don't get me started.

Weejock wrote:

As you can see due to the extra servicing expense and possible expensive to fix problems it was quite popular to actually delete the DPF from the system although illegal to do so. To prevent that the DPF was added to the MOT test, if a vehicle was fitted with a DPF from the factory it must physically still have one come MOT time (the same as the CAT). Whether they know what's actually inside the DPF shell is another matter!

Just to clarify this point, it's not illegal to remove the DPF from the car, and map it out

But the DPF needs to be fitted for an MOT. If the DPF is missing, it "should" be an instant fail, regardless of emissions
And I expect VOSA/DVSA or whatever they are called will take a dim view if you happen to be subject to a roadside check

However, if the DPF looks like its there, and there are no warning lights on the dash, then who knows

The bigger problems arise with earlier systems that needed much higher temps to force the soot to be burned off by chemical reaction.

Most now get away with this as PSA have been doing for a fair while now and put on some V6 HDi units, is to use an additive that brings down the temprature required for that reaction to happen so is much easier to get to and thus diesels that do shorter journeys are not as susceptible as they once were to clogging.

TBH its horses for courses. When they burn hotter they cause more NOX but less CO2. Burn cooler more CO2 less NOX...

Do away with them and just have a big water tank and fine mist in the exhaust to trap the soot and drop it on the road and job done  FFRR MY06 facelift With TDV8 Alloys Zeros/ATR's
Mantec Sump Guard, Rigid Load liner, MY10 BT upgrade.

Mikey wrote:

Weejock wrote:

As you can see due to the extra servicing expense and possible expensive to fix problems it was quite popular to actually delete the DPF from the system although illegal to do so. To prevent that the DPF was added to the MOT test, if a vehicle was fitted with a DPF from the factory it must physically still have one come MOT time (the same as the CAT). Whether they know what's actually inside the DPF shell is another matter!

Just to clarify this point, it's not illegal to remove the DPF from the car, and map it out

But the DPF needs to be fitted for an MOT. If the DPF is missing, it "should" be an instant fail, regardless of emissions
And I expect VOSA/DVSA or whatever they are called will take a dim view if you happen to be subject to a roadside check

However, if the DPF looks like its there, and there are no warning lights on the dash, then who knows

surely you've just contradicted yourself? I mean if it's not illegal why would DVSA take a dim view at a roadside check?

I believe it is illegal to remove it if it was fitted as standard, as the car would be considered to be an unroadworthy condition. But like most of these sort of things, the chances of getting caught are probably very slim.
You could as you've alluded to remove the insides of one and put a bit of pipe through the middle then refit it, and still pass an MOT as it's only a visual check.

Mustard wrote:

@ buy a petrol


Ok thanks, why do people complain about them ?

Are the expensive to replace / do they hinder performance ?

Is it Illegal to remove them / interfere with them ?