Filter fail

Diesel particulate filters are designed to burn off harmful nitrogen oxides and other tiny particle emissions at blast furnace temperatures, leaving only an ash residue. No doubt this stuff is better incinerated than lodging in the lungs, given these microscopically fine soot particles are known cancer triggers.

Manufacturers claim the filters are lifetime components, similar to the catalytic converter.

“Under Australian conditions, there’s not a hope in hell,” says technician Bryce Spiteri, who sees clogged, inoperative DPFs on a daily basis.

Replacement costs for these alleged “lifetime” diesel particulate filters can be eye-watering: $4000 to $6000 is not uncommon. And the end cost to the customer typically doubles to $8000-$12,000, when diagnostics, plus removal and replacement labour charges are added.

Many DPFs are failing just out of the warranty period at around 100,000 kms but too often, much sooner. This is very early in the lifecycle of an old technology, non-common-rail diesel engine. Typically those engines would routinely deliver three times that distance without major maintenance.

Failed DPFs share some common traits. “It can be spasmodic,” says Spiteri. “Some of it is age and the failure rates go up with kilometres travelled. We see DPFs with a lot of accumulated soot and ash and even the passive regenerations aren’t enough to clean them out while driving. They get to the stage where they are blocked and have to be physically removed.”

Alarmed at the growing number of DPF failures through his workshop, Frank and Bryce Spiteri began development of an ultrasonic cleaning process that could clean out many blocked filters declared dead by dealer service departments. It took three years and $300,000 in investment, but his company, DPF Regen, is now bringing filters back from the dead in a couple of days for under $500 a pop. Plus labour.

Business is booming alongside their existing Bosch Service centre, drawing business from branded dealerships as well as truck and bus companies.

The European marques can generally be resuscitated, Frank Spiteri says, and make up 70 percent of his throughput. But many makes are deemed throwaways.

He is seeing a lot of Holden Captivas and Nissan Navaras that fit that description but also a lot of DPFs with the back end blown out, the result of dealership service departments repeatedly trying what’s called a forced regeneration.

“They don’t even know how to measure differential back pressure, so they try forcing the regeneration repeatedly. One told us they’d tried six times. Well, the thing just melted.”

Bryce Spiteri adds BMW’s embedded onboard data suggests a service life of 250,000km for the DPF in an X5.

“That might be right in Germany where you are on the autobahn at 130 kays for an hour each way but those aren’t typical Australian conditions” he says.

He has seen them blocked as low as 60,000km under our conditions.