We are seeing a steady increase in the number of customers having difficulties with Diesel Particulate Filters on their cars. There has also been a great deal of discussion recently focussing on how this hidden - and sometimes expensive - problem has suddenly hit many driver unawhare that these devices existed.
We already outline our DPF cleaning / regeneration service elsewhere on the site. However thought we would cover the DPF, it's problems, causes and solutions in more detail.
The Diesel Particulate Filter (DPF) removes carbon from the exhaust gases of diesel engined vehicles - hence no more sooty black exhaust gases. Unfortunately the filter works by collecting the carbon within the filter, and of course like all filters, eventually becomes full.
The DPF filter is not like other filters; it's an integral part of the vehicle exhaust system and is also an expensive item. More importantly the filter has a cleaning cycle that is managed by the vehicles engine/exhaust management system.
This self cleaning cycle is the area causing difficulties for customers, particularly customers using their cars for mainly short journeys.
Under normal driving conditions the DPF filter is cleaned during a long journey when sufficient heat can be generated to burn off the carbon that builds up in the DPF filter. This process is completed automagically without informing the driver.
However, cars that are mostly driven for short journey this cleaning cycle is unable to start and/or complete sufficiently to reduce the carbon in the filter before it becomes over full and a fault is indicated.
The DPF fault indicator is not that there is a fault, or that the DPF is yet full. However it does indicate the filter is FILLING and has been unable to clear.
The most common means to try and clear your DPF yourself would be to take the vehicle on a long journey; sufficient enough to fully warm the car AND run the cycle (approx an hour in total).
Does this work ? In short, only sometimes. Whether you are able to clear the filter will depend on whether your car enters the cleaning cycle, largely outside of your control.
A better approach is to drive the vehicle more regularly on longer journeys before the DPF fault being indicated (of course this does not help you once the light is on!).
When we undertake the cleaning process we are able to connect our diagnostics computer to the vehicle, and following the manufacturers process, manually force the car to enter it's cleaning cycle. Once this is complete the car needs to be driven. with the computer connected, while the cleaning process completes.
Once your DPF has been cleaned there are several steps you can take to avoid the problem again;
The Diesel Particulate Filter can be removed from the exhaust system. This will not effect the operation of the vehicle (provided it is completed competently) and while exhaust emmisions are part of the MOT test, removal would usually not cause a vehicle to fail the MOT test based on emmisions. However as the vehicle ages and the MOT requirements become more stringent there is nothing to say that removal of the DPF filter will cause an MOT failure in the future.