The DPF or DIesel Particulate Filter is a common issue on modern diesel vehicleS. The most common enquiry we recieve is my dpf needs cleaning and how much is it? UNfortunately this is the wrong approach in most cases. What you should be asking is my dpf has an issue what has caused this?

DPF issues are almost always a symptom of another issue or mechanical fault in some cases its just down to driver/operator error. Determining the route cause of a dpf issue is most important as if this is not addressed the problem will reccur again quickly.

The way we would operate is to carry out our dpf Assessment to ensure the vehicle is operating correctly and will continue to operate correctly after repairs are made.

A dpf shouldn't need cleaning reqularly as it should be a self maintaining system. DPF cleaning is only necessary if the filter has been contaminated, has an unsafe soot loading or in the case of off car cleaning the ash limit of the filter has been reached.

To understand this further basic dpf operation needs to be understood - So an engine produces smoke which contains particulate matter this matter is harmful to atmosphere. the dpf was developed to catch the harmful particulates in exhaust gases and store them until they can be burnt off to reduce particulate emissions and emitted to the atmosphere. When the soot (particulates) level in the filter is deamed high enough a regeneration is carried out. This is where exhaust temp is raised to a level that burns the trapped soot in the filter and expells co2 and other less harmful gases produced by complete combustion. When the soot is burned off a small amount of ash is left behind. This is a crucial point to pay attention to the process of regenerating always creates ash the ash is generally to large to pass through the filter matrix so is stored. Eventually yhe ash levels in the dpf will reach a point where the capacity of the fitler is serious deminished. This is why dpfs do not last forever and become more troublesome with higher mileages. Manufacturers recommend at around 100k to 150k miles the dpf is replaced to ensure correct operation. In most cases the cost of a replacement filter at the 100k plus mileage limit is not financially viable and can write off a car.

This brings me on to the next topic on and off car cleaning of DPFs, ON car cleaning works wonders for Soot accumualtion issues but it cannot and will not remove ash as it relies on chemicals moving in the direction of exhaust flow and filter design preventing ash making it through the filter. So on car cleaning is a viable option for vehicles which have had a mechanical issue and the soot loading is to high to safely regenerate without the risk of a catastropic fire.

When dealing with higher mileage filters the best  option is to remove the filter and clean off car.

Off car cleaning requires specialist equipment to reverse the flow through the filter to remove not only soot but ash, oil  and other contaminates. Off car cleaning is effectivley a refurbishment of the filter and not just a clean as it removes Ash and soot not soot alone like on car cleaning.

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