Demand for DPF cleaning and replacement units continues to be strong as the diesel vehicle parc ages and more customers bring their car or van to the garage with the DPF light showing.
While this problem can be solved in most instances through effective cleaning, it is essential to identify the root cause of the issue to prevent repeat DPF failure. David Eszenyi, Commercial Director at leading remanufacturer, Ivor Searle, explains:
“If a DPF keeps failing, the filter itself is typically not the real problem. In most instances, an issue upstream in the engine or emissions system is causing excess soot, which prevents the filter from cleaning and regenerating itself properly. If the DPF is cleaned or replaced without diagnosing and repairing the cause, it is likely to fail again, sometimes within just a few days. The common causes of DPF failure are generally related to engine problems, faulty sensors and oil and additive issues.”
“Engine problems include boost leaks and split hoses where small splits in intercooler or intake hoses can let air escape after it has been measured by the Mass Air Flow (MAF) sensor. The ECU may then add excess fuel, which creates extra soot and blocks the DPF faster. Contaminated EGR valves, which have become clogged with carbon and stick open, also create excess soot which is sent back through the engine and into the DPF.”
“Leaking, worn or blocked fuel injectors also lead to poor combustion, unburnt fuel, and heavier soot build-up. Turbocharger seal failure also causes exhaust contamination due to the worn seals allowing oil to enter the exhaust system. Oil can burn into a thick residue in the exhaust, coating the front of the DPF and making it harder for the filter to regenerate and clean itself.”
“Today’s diesel vehicles typically utilise glow plugs to raise exhaust gas temperatures while driving and not just when the engine is started from cold. If a glow plug or control module has failed, the ECU is likely stop the automatic DPF cleaning and regeneration process from taking place. Incorrect DPF pressure readings can also cause problems. The sensor checks how much soot is in the DPF by measuring pressure before and after the filter. If the sensor is inaccurate, or its pipes are split or blocked, the vehicle may not start a cleaning cycle when required. Stored fault codes can also be problematic where unrelated faults, such as a service warning or thermostat issue, can cause the ECU to stop DPF regeneration as a precaution.”
“Use of the incorrect engine oil can also cause ash deposits in the DPF. It is important to use the correct specification, vehicle-specific oil as some standard engine oils create ash when they burn. Unlike soot, this ash cannot be removed by normal DPF regeneration and can permanently block the filter channels. A low or empty DPF additive tank can also cause excess soot. Some vehicles use Particle Additive Tank (PAT) fluid, also known as Eloys, to help burn soot at lower temperatures. If the additive tank is empty, or the vehicle computer has not been reset after a refill, the DPF may not clean itself properly.”
“Interrupted DPF cleaning cycles also cause soot to build-up, as :the DPF needs sufficient heat and time to finish cleaning itself. If the vehicle is switched off during an active regeneration, or is mainly used for short trips, the soot may only partly burn away and continue to build up in the filter.”
“To stop the DPF problem recurring, it is recommended to carry out a full diagnostic evaluation during a drive cycle and not just scanning the vehicle in the workshop for fault codes. Technicians can gain a wealth of information from live engine data, including exhaust temperatures, EGR operation and boost pressure, to find the root cause of the blocked DPF and prevent repeat failure.”
Utilising Flash Cleaning technology, Ivor Searle’s environmentally-friendly process delivers industry-leading levels of cleanliness by removing all soot deposits, including PM10 particles, cerium oxide deposits and oil residues from the DPF. To find out more about Ivor Searle’s professional DPF cleaning service, which is covered by a no quibble 12-month unlimited mileage warranty, please call the Ivor Searle sales team on 01353 720531.
Filed under: DPF cleaning UK, Ivor Searle DPF