Many diesels have an extra tank for a product called AdBlue, a blend of high-grade urea and de-ionized water. “Another engineering marvel,” says Frank Spiteri. “The government wants emissions down. The engineers say this is impossible with the engine characteristics of a diesel so how about we just urinate in the exhaust system and get the ammonia to sort out the oxides.” While not exactly a technical description that’s pretty much what happens. The AdBlue is injected into the exhaust, not the fuel tank.
AdBlue reduces nitrogen oxide emissions but also removes much of the smell that emanates from a DPF in regeneration mode.
Cost cutting, usually by commercial vehicle fleets seeking to make the AdBlue mix themselves is also causing major problems.
Lower grade urea and the use of use of tap water instead of the de iode-ionized stuff have triggered sandstsandstone like calcification in at leat least one case study.
“We see a bit of moon rock, as we call it, but mostly in commercials and buses where the AdBlue muffler is choked up,” says Bryce Spiteri.
With some truck AdBlue mufflers costing upwards of $10,000 each, he has seen customers clog them up again as little as 18 months later. The cause? Calcium residue in the water.
Biodiesel may be warmly embraced by vested interests but along with water contamination, it’s viewed as the work of the devil by many diesel technicians.
“While fuel quality appears to be getting better, horror stories of damaged injectors or pumps and huge repair bills all relating to dirty fuel still abound. Sure, a good old Landcruiser 60 series can run on bio-fuel and irregular maintenance but anyone with a latemodel diesel (and that means most diesels from year 2000) running electronic injection need to be much more aware,” says Andrew Leimroth from Berrima Diesel.
For all the efforts of the world’s engineers, the battle to produce a truly low-emissions diesel engine is a story of work-arounds and compromises in an effort to clean up the tailpipe.
“There’s no viable solution so you rebreathe your exhaust, put a filter on the exhaust system and squirt urea into the gas,” said one engineer. “What could possibly go wrong?”
Mercedes is one of only two companies to concede stop-start running is a problem for diesels.
“If a vehicle is used purely for short runs and never gets a decent drive at highway speed then that could create an issue with the DPF” it says.
“Vehicles used for short trips can see … parameters are not met and the diesel particulate filter becomes blocked and requires intervention from the service department.”
Replacement DPF prices range from $2500 to $4000 plus labour. The use of low-ash oil is also a requirement.
“If the incorrect oil is used the DPF can become contaminated and will not clean as part of the regeneration. This could cause the need to replace the DPF prematurely.”
Mercedes sets no service replacement life for the DPF and has no schedule in place for vehicles that have a build-up of carbon in the intake and EGR systems.
Benz blames “poor fuel and operating conditions” for the slue sludge.
“If an issue is detected this may see the need for retail repair to clean the manifold and or EGR systems re l r em by removing and cleaning.”
And in case studies Wheels has seen on Mercedes And i s seen on Models that is a $3000 job.
All PSA diesels are fitted with particulate filters with prices ranging from $1200 up, plus labour. Service life is “very dependent on driving conditions and style” but company says it considers 220,000km “normal”.
Replacement filters span $1430 to $3480 and are not a component the company says is “expected to need changing under normal operating conditions.” It says it has no specific servicing policies for DPF equipped vehicles, as functions will “automatically commence.”
No response on carbon build-up and no mention of it in owner handbooks or service schedules.
Major dealerships however are charging customers $200-$300 to carry out a “diesel decarb and injector clean” for a problem the factory doesn’t acknowledge.