The DPF warning light comes on - now what? How to clean a diesel particulate filter

Diesel vehicles have long been considered particularly environmentally friendly. Low fuel consumption and the possibility of using biofuels gave diesel drivers a clear conscience. However, the self-igniter has proven to be a dangerous source of harmful substances.

Soot , an inevitable by-product of diesel combustion, is a major problem. Soot is the residue of burned fuel.

In older diesel vehicles without any exhaust gas filtration, the solidified substance is released into the environment. . When inhaled, it is just as dangerous as carcinogens such as nicotine and cigarette tar. Therefore, car manufacturers have become legally bound to equipping new diesel vehicles with an efficient exhaust gas filtration system .

The effect is only temporary

Unlike the catalytic converter in gasoline vehicles, the diesel particulate filter is only partially a catalyst. DPF is what its name says: it filters soot particles from exhaust gases. But no matter how big the filter is, at some point it can no longer maintain its filtering capacity. DPF is self-cleaning .

Soot is burned to ash by artificially raising the temperature of the exhaust gases , which leads to a decrease in the volume remaining in the filter. However, a certain amount of ash remains in the filter as a residue, and over time the diesel filter is filled to capacity.

Self-cleaning program has run out its capabilities and the engine control unit signals an error, to which indicates a control light on the dashboard .

This warning cannot be ignored. When the DPF is completely clogged, there is a risk of severe engine damage. Before this happens, engine performance is clearly reduced and fuel consumption increases.

Repair is required by law

A perfectly functioning diesel particulate filter is required to pass the inspection. If the inspection service detects a clogged filter, the issuance of a maintenance certificate will be refused. The MOT or any regulatory board generally recommends filter replacement. Depending on the car model, this can be quite expensive. New filter and replacements cost a minimum of 1100 euros (± £972) , and possibly more. However, there is an alternative .

Cleaning instead of buying a new filter

There are proven and certified methods to clean the DPF to keep it as good as new. Features:

– burning cleaning
- rinse cleaning

or a combination of both procedures.

To completely burn the dismantled DPF, it is placed in a kiln where it is heated until all the remaining soot is burned to the ground. . Then the filter is blown with compressed air until all ash is completely removed.

Flushing is actually cleaning the filter with an aqueous cleaning solution. . With this procedure, the filter is also sealed on both sides, which is necessary for adequate cleaning of the DPF from ash. Ash accumulates in closed channels. If the filter is only cleaned in one direction, the ash remains in place, what makes filter cleaning ineffective .

Branded products are inadequate

This is the main problem with homemade filter cleaning solutions. . There are plenty on the market miraculous solutions promising perfect cleaning of the particulate filter. Unfortunately, this race was joined by famous companies , which are best known for their excellent lubricants.

All of them advertise solutions for pumping into the threaded hole of the lambda probe to clean the filter. As stated before: complete cleaning of the filter requires treatment on both sides . During installation, only one-sided cleaning is possible. Therefore, these homemade solutions are not entirely suitable for cleaning filters.

The problem is more serious

The available methods are only partially effective. The injection method has another problem: cleaning agent, mixed with soot and ash, can form a hard plug . In this case, even the most severe cleaning methods, such as calcination at a temperature over 1000 °C , do not work.

The damage to the filter is so serious that replacing it with a new element is the only way out, and this is sad. Professional cleaning with certified efficiency available starting at £180 , which is 1/5 the cost of the cheapest new DPF .

Do-it-yourself disassembly saves money

Dismantling the particulate filter is not very difficult , and you can save money by doing it yourself and sending it to your service provider. Worst case it might break. lambda probe or pressure sensor. The service provider offers drilling and repair of the threaded hole as an additional service. It is always cheaper than buying a new particulate filter.

When removing the particulate filter, carefully inspect the entire exhaust pipe. The filter element is by far the most expensive component of the exhaust system. In any case, when the car is raised, it is a good time to replace all rusted or defective exhaust system components.

Reusing a lambda probe is a matter of philosophy. A refurbished DPF does not require a new lambda probe or pressure sensor. . In any case, replacing the part in this case will not hurt and will set a new starting point for the entire assembly.

Always looking for a reason

Typically, the service life of the particulate filter is 150 000 km under various driving conditions. Longer motorway distances of more than an hour should regularly occur. When driving a diesel only for short distances, the engine and exhaust temperatures required for the self-cleaning DPF are never reached.
If the DPF clogs sooner, a serious engine defect may be the cause. In this case, engine oil penetrates into the combustion chamber and the particulate filter. The reasons for this may be:

– turbocharger defect
– Defect of a laying of a head of the block of cylinders
- defective oil seal
– defective piston rings

There are procedures for investigating these defects . Before installing a new or refurbished diesel particulate filter, check the engine for this kind of damage. Otherwise, the new component will soon become clogged and engine damage may worsen. Filter replacement is useless.