When your DPF is blocked and the car won't perform a re-gen, then chances are a good highway thrashing is not going to solve the problem any more and the DPF will have to come off to be properly cleared of clogged up soot. Replacements are outrageously expensive and professional cleaning is not cheap, plus the DPF must be sent away, but it is possible to do at home for very little money. You just need a suitable place to do it and be prepared for the mess...
1. Compressed Air Blowout - This is the first step we took and may be all that is necessary if the DPF is not completely blocked. The only way I've seen so far with air compressed at enough pressure to clear stuff from the DPF is to use a 'bead-blaster' or 'bead-seater' designed for blowing tyres on wheel rims at about 90 psi. I doubt a tyre-shop is likely to let you use their equipment to blast a load of soot out of a DPF, as it is messy business, but if you know someone or have access to one then it's very effective. The DPF needs clearing out backwards, so secure it to the floor somehow (or get someone wearing ear-defenders to put their foot on it) and aim the bead-blaster into the flexi-pipe leading to the exhaust.
2. Cleaning Solution - This is a much deeper clean than just blowing the DPF out and will take a couple of days with it removed from the car.
- Seal the front end of the DPF as water-tight as possible. Re-fit the sensors to their holes and block off the small metal tube. Use thick plastic material to seal the large front opening of the DPF, tied tightly around the rim. Chances are it will still leak some liquid from around this aperture.
- Obtain suitable DPF cleaning-solution. I first used Wynn's Professional Off-Car DPF Cleaner, which cost me £27 for 5L. Quite pricey, but it certainly does the job. The Wynn's solution does smell very similar to a couple of cleaning products that were already available to me at work, both made by Autosmart, but I'm sure other companies make similar - TFR (Truck Film Remover), a strong de-greasing and cleaning solution, and G101, a very strong soap solution, so if you have access to these products it may be cheaper to get a few litres of each of them instead. I ended up using about 5 litres of neat TFR and the same amount of neat G101 after most of the Wynn's had leaked away and we have since cleaned out the DPF from an E81 120d, which worked a treat.
- Place the DPF in a bucket and leave the solution to soak into the DPF over at least 12, but preferably 24 hours. Even if it is impossible to stop fluid leaking from the DPF, the bucket will fill to a level where the pressure equals out and the DPF can be fully filled with solution as long as you have enough.
- Remove the plastic and jet-wash the DPF out from back to front, with the lance into the exhaust outlet. Be careful where you do this as it is very messy, with a lot of thick black soot being ejected, so try and do it directly down a drain as it cover a large area if done onto the ground. If you do not have access to a pressure-washer, then you could try flushing it with buckets of water poured in quickly, but this is not going to be as effective.
- Rinse the remaining soap from the DPF by leaving a hose to run through it and / or pouring buckets of water through. This will minimise the car 'blowing bubbles' once the DPF is refitted and still has soap / moisture inside!
- Leave the DPF to drain and dry out for as long as possible and refit it to the car.
- Give the car a 'spirited' highway drive, preferably in 3rd gear if it is manual, to blast remaining loose debris from the DPF. If the car was showing error codes for the DPF only and these have been reset, at this point the car should begin to re-gen by itself.
