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Your Van’s Diesel Particulate Filter

Forewarned is forearmed.

Learn about your van's Diesel Particulate Filter and avoid costly repair bills

You may be among the many drivers who are blissfully ignorant of the fact that your new diesel van even has a Diesel Particulate Filter. If you are, then it might pay you to read on:

Improved fuel economy means that diesel vans have increased in popularity over the last few years, but drivers should be aware that potential fuel savings could be outweighed by repair bills if their van is not looked after properly. European rules which came into force in 2009 mean that all diesel vans are now fitted with a Diesel Particulate Filter (DPF). The DPF works as a filter to trap soot and harmful particulates in the exhaust, reducing emissions by around 80 per cent. Great news for the environment and your road tax bill!

But despite these benefits, the DPF could cause a headache for those stop-start urban drivers who are not travelling long distances. The DPF has a self-cleansing process built into the software of the van which becomes effective when the exhaust reaches a high temperature, so after a long journey they are meant to regenerate and re-cleanse. If you are not doing longer-runs, the exhaust temperature doesn't rise sufficiently so regeneration won't happen effectively. This could lead to the need for a new DPF being fitted, which would cost at least £1000 plus labour costs.

Forewarned is forearmed.....

Don't despair. There is no need to trade in your faithful diesel van. There are some easy steps to take to avoid your DPF clogging:

  1. The filter is designed to regenerate passively on fast A-road runs when the exhaust temperature is high. Simply driving at speed for 15 minutes should do the job.
  2. Because some vans just don't get this kind of use manufacturers have built in 'active' regeneration to take control of the process. When the soot loading in the filter reaches a set limit the vehicle's engine management computer will initiate post combustion fuel injection to increase the exhaust temperature and trigger regeneration. If the journey is too short while the regeneration is in progress, it may not complete and the warning light will come on to show that the filter is partially blocked. So make sure you know what your DPF warning light looks like. If you see it a 15 minute drive at a speed greater than 40mph should clear the warning light.

How to recognise when your van is in 'active' regeneration

You may notice the following symptoms from your van during active regeneration:

  • Engine sounds different
  • Slight increase in fuel consumption
  • Cooling fans running
  • Deactivation of automatic Stop/Start
  • Hot exhaust with acrid smell
  • Increased idle speed
  1. If you ignore the warning light and continue your normal stop-start driving pattern soot loading will continue until the filter is around 75% full when you will see other engine dashboard lights come on too. At this point you will need to take the van to a specialist for forced regeneration.

What can stop normal regeneration from happening?

  • Short stop-start journeys where the engine doesn't reach normal temperature.
  • The wrong oil. DPF vans need low sulphur/low ash engine oil.
  • Exceeding the oil counter/service interval.
  • A low fuel level. As a general rule a quarter of a tank is required.
  • The van is low on additive.
  • A warning light on or diagnostic trouble code logged in the engine management system may prevent active or catalyst regeneration.

So as far as looking after your DPF is concerned, prevention is better than cure. A standard DPF is designed to last well in excess of 100,000 miles if regeneration happens regularly. If you look after your van properly you will be rewarded with thousands of hassle free miles while saving thousands of pounds on unnecessary repair bills!