How to clean a DPF

DPF Filter problems - Cleaning your DPF

"Turning off the DPF warning  light."

What is a DPF?

It is a particulate filter and helps to reduce the harmful particles which come from a diesel exhaust.

The filter essentially catches the harmful unburnt particles and when the engine gets hot enough it burns them off. Why does it need cleaning? How do you clean a DPF? What methods are best for stopping the DPF getting clogged up in the first place? Let's cover these questions in this article and we'll provide a step by step DPF regeneration guide.

There are a few common mistakes people make with additives that can actually damage your DPF permanently. So we'll cover this in this article later, and we will discuss the best methods to clean your DPF filter.

The DPF is located within the exhaust system, generally near to the engine. It should not be confused with a catalyst, whose primary job is to remove or reduce the exhaust emissions of Co2 and other gases.

The DPF is purely there to capture soot and particles from the exhaust.

The nearer it is to the engine, the hotter it gets, and the more effective it will be. Where manufacturers mount them some way from the engine we hear of lots of problems with blocked DPF filters. A temperature before the Turbo Charger that exceeds 700 °C is required on most cars for a regeneration cycle.

See our new "How to Clean a DPF" video.

exhaust-inside

Why does the DPF need regenerating or a clean?

If you only do short journeys or keep the engine in low revs these particles will build up to the point that the DPF gets completely blocked (90%).

When this happens the engine will not run and you need to replace the DPF filter.

Hopefully prior to this your cars ECU will notice the build up and warm you to change your driving style to burn off the soot.

The warning light comes on to show that you need to alter your driving style to clear the DPF filter URGENTLY and this should NOT BE IGNORED.

The DPF may become too blocked to clear by driving, so don't ignore the warning light.

Act immediately or your only option will be to take the car to a garage for repair. There are no additives or methods that will clean a BLOCKED DPF.

There is a narrow window where a mechanic can clean the DPF by forcing a regeneration but after this narrow window your only option is to fit a new filter to your car.

Some cars are fitted with DPF's have a separate tank for a fuel additive which allows the engine to burn off the carbon at a lower temperature.

standard-catalyst

The DPF will block up if you only do short low RPM journeys leaving you with a massive repair bill.

DPF Cleaning Method

How to clear a DPF warning light by DPF cleaning.

Your cars handbook will have a section on cleaning your DPF or entering a regeneration cycle so we suggest you consult this as each car is slightly different.

Here is a general DPF Cleaning guide that should be effective on most DPF's.

  1. Ensure you have plenty of fuel 25 litres is usually the minimum a car needs to trigger regeneration.
  2. Make sure there are no engine warning lights on - just the DPF warning light.
  3. Warm up the engine to operating temperature, then drive it for 15-20 minutes at constant speed on a motorway in a lower gear, you want the RPM to sit at around half way,  and for most engines this is somewhere around 1500-2000 rpm around 40mph.
  4. Use a slower speed and lower RPM for 10 minutes, then repeat with another hot 15-20 minutes at around 2/3 of your RPM range.
  5. Aim to keep the revs above 1500rpm for this period. The heat generated will help clean the DPF filter and the cars Regeneration cycle will usually kick in under these circumstances.
  6. Keep this cycle going for around 45 minutes to an hour and a half for best results, it can be spread over multiple drives but you must ensure the engine is hot and do at least 2 sets of 15 minute hot drives each time.
  7. It is good practice to make this routine a part of your weekly drive, before the DPF warning light even comes on.

Warning: If the engine is misfiring or in limp home mode you should avoid high revs, build up the heat slowly and steadily and go for a longer run. Ideally, you should take the car to a mechanic if it is misfiring to avoid further damage or problems.

So the cleaning method generally requires an additive that assists the burning of carbon and enough heat to activate the burning process.

It is a good idea to take the car for a spirited drive regularly and to avoid short journeys where the engine does not warm up fully.

High RPM driving will also help keep the DPF clean, and in the case of most diesel engines you will not suffer a significant drop in your fuel economy doing so. I personally found just 10% difference in fuel economy between ultra careful driving and keeping in the upper part of the rev range.

These short journeys are the single biggest culprit in blocking a dpf with soot and carbon.

DPF Cleaning fuel additives

Add some BG244 to your tank and go for a long motorway run at 70mph again keeping the revs above 2000 rpm. Other cleaners are available but BG244 is in our opinion the most effective on the market and is good at keeping the DPF filter clean.

Some cleaners are designed to maintain your DPF and keep it clean, others are designed to remove the carbon. The key difference is if they raise the engine burn temperature or not.

WARNING: Using an additive that raises your engine burn temperatures is not good if you are in a DPF cleaning cycle, as the engine is already raising it's temperature and in many cases this can result in damage to your DPF filter.

Professional DPF specialists often see heat damaged DPF's, and this is primarily caused by using the wrong additives.

How to avoid a blocked DPF.

Use good quality fuel. High Cetane fuel from major brands is laden with additives which help burn off the particles.

Cheap fuel usually adds to the problem. TorqueCars recommend Shell fuel, our tests have shown that this burns cleaner and leaves less deposits in your engine.

Avoid short journeys where the engine does not warm up fully and trips where the car is not able to maintain 2000rpm for 5 mins.

Use a good quality fuel additive such as BG244 to maintain a clean efficient engine.

Can the DPF be removed?

Yes it can but this this not generally legal in most countries and territories. A car which is supposed to have a DPF filter will fail it's annual inspection and will struggle to pass an engine emissions test.

The cars ECU will be setup to run with a DPF and if it's removed you might end up with rough running, error codes or an engine that is stuck in limp home mode (ECU's can be reprogrammed to cope with a DPF removal though).

If your DPF keeps getting blocked then this could be down to your driving style, or the engine could be running too rich, either case should be investigated further to prevent a recurrence of a blocked DPF.

Discuss DPF issues and problems with our members in our forum.

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2 Responses to “How to clean a DPF”

  1. Ryan Lomax says:

    Hi im Ryan the other day my warning light come on particular filler drive to clean than not 2.min later it come bk on saying exhaust filter at limit and the comes on service on and puts me in limp home mode and guy come out payed 250 for a dpf cleaning but at the end hes putted in to the obd and said 1/3 glow plugs our showing aswell as the particular fillter at limit drive to clean so he said he would come bk and clear it when i did the glow plugs well they was dont 2 days later he come bk plugged in the obd and cleared it drive not 30 min and it come bk on all tje same PLEASE HELP!!!! It a ford transit custom 2015 van 2.2TDI

  2. Paul says:

    Thanks for such inspiring education. My question is that will the car have a problem should you remove the dpf?

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