When a diesel comes in with a blocked DPF, a garage has three real options. Try a forced regeneration or an on-car flush, order a new filter, or take the filter off and have it cleaned properly. Plenty of garages take the third route and send the filter out. Here is why it makes sense for a workshop to outsource DPF cleaning, when it doesn’t, and how to make the job run smoothly.
What a forced regen can’t do
A forced regeneration is often the first thing a garage tries, and sometimes it works. It raises exhaust temperature to burn off soot. The trouble is that soot is only part of what’s in the filter.
The rest is ash. DieselNet’s technical summary describes it as the incombustible material left behind following filter regeneration and soot oxidation, coming mainly from lubricant additives, fuel trace elements and engine wear. However many regens a filter has had, the ash stays put. On a high-mileage car or van, that is often why a regen brings the readings down for a week and then the light comes back.
Getting ash out means taking the filter off and cleaning it through. That is the point where most garages stop and ask whether they want to do it themselves.
Why garages outsource DPF cleaning instead of doing it in-house
Off-car cleaning needs dedicated equipment, space to run it and somewhere to deal with what comes out of the filter. For most independents, the number of DPF jobs doesn’t justify that. Sending filters out turns a capital cost into a job cost you can quote.
You do the diagnosis, the removal and the refit, which is the skilled labour your customer pays you for. The cleaning happens elsewhere while the bay goes back to work.
We test every filter before and after cleaning. You get the readings when you collect it, which makes it easier to explain the job and the bill.
If the filter is sound, cleaning keeps the original part on the car. Your customer avoids the cost of a new unit, and you avoid chasing parts.
Our view: most garages are better off owning the diagnosis than owning the machine. Finding out why a filter blocked is where a good workshop earns its reputation. The clean itself is a specialist step that is easy to hand on.
When sending the filter out is the wrong call
Off-car cleaning isn’t the answer to every blocked DPF. Before you take a filter off, it is worth ruling out the cases where it won’t help.
- The filter is physically damaged. A cracked or melted core won’t be fixed by cleaning. We check every filter for cracks, a melted core or housing damage before we start, and we will tell you before going any further so you can talk to your customer about replacement.
- Something upstream is still wrong. A sticking EGR valve, a faulty pressure or temperature sensor, worn injectors or oil getting into the exhaust will load a clean filter again quickly. Our guide to engine problems that keep blocking a DPF covers the usual causes.
- It only needed a regen. If the vehicle simply hasn’t been able to complete regenerations and the filter isn’t carrying much ash, a successful forced regen may be enough. Your readings will tell you.
How trade drop-off works with us
Our trade service is built for garages that have already diagnosed the problem and want the filter cleaned. Here is how a job runs.
A filter coming off a car on the ramp, then going into our current cleaning machine at the Fenton workshop.
For the full service, including who sends us filters, see our trade DPF cleaning service for garages and workshops.
What to quote your customer
Knowing our side of the price lets you quote the whole job with confidence.
| Filter type | Our cleaning price |
|---|---|
| Car and van DPFs (drop-off) | From £100 + VAT. Prices may vary depending on the filter, its condition and the job. |
| Larger commercial and HGV filters | Priced separately, on quote. Send us your filter details or part number. |
| Postal filters | Quote and return times depend on your location. |
We confirm the price before any work starts. For HGV and larger commercial work, our new DCS-20L machine supports HGV DPF cleaning at the workshop, and our HGV DPF cleaning page explains how we quote bigger filters.
Before you refit the cleaned filter
A clean filter on a car with an unfixed fault will be back. A few checks at refit make the job stick:
- Fix whatever caused the blockage before the filter goes back on, and tell the customer what you found.
- Check the sensors and pipework around the DPF, including the differential pressure sensor pipes.
- Follow the manufacturer’s procedure after refitting, including any adaptation or reset the vehicle’s software needs.
- Clear the codes and road test so the vehicle can complete a regeneration under normal driving.
It also protects the MOT. Since May 2018, diesel cars with a DPF get a major fault if the tester can see smoke of any colour from the exhaust. A sound, clean filter and a fixed engine fault are the best way to keep it clear.
Frequently asked questions
Is it worth a garage buying its own DPF cleaning machine?
For most independent garages, the number of DPF jobs doesn’t cover the cost of the equipment, the space and the running costs. Sending filters to a specialist lets you offer the service without the investment, and you still earn on the diagnosis, removal and refit.
Can every DPF be cleaned?
No. A filter with a cracked or melted core, or housing damage, can’t be restored by cleaning. We check for damage before we start and tell you straight away if a filter isn’t worth cleaning.
How long does off-car DPF cleaning take?
We aim for one working day on drop-off cleans, but it can take longer depending on the filter. We’ll give you a time when you book. For posted filters, return times depend on where you are.
Is off-car cleaning better than an on-car clean?
They suit different jobs. On-car cleaning and forced regens can work where the filter is mostly soot. Once ash has built up, the filter needs to come off and be cleaned through. Our comparison of on-car and off-car DPF cleaning covers the differences.
Related reading
Send us your next blocked filter
Tell us the vehicle and the filter, and we will confirm the price and give you a time when you book. Call 07827 533529 or get in touch online.
