Before And After The DPF

Successful Dealer Staff April 10, 2012

Before and after the DPF

Any truck built in 2007 and later requires an additional maintenance interval: servicing the diesel particulate filter. Cleaning the filter element removes accumulated engine oil ash, particularly for heavy-to-severe-duty trucks in high-idle on-/off-road applications. While ash in the DPF typically remains loose, a small amount of carbon may adhere tightly to the DPF’s ceramic walls, forming gooey or even hard deposits, especially if the engine is not operating properly.

While thorough cleaning may result in better fuel economy and more miles, inadequate cleaning can compromise the filter’s life and warranty. But simply learning when to clean is not enough; know the cleaning procedure and the vendors for an effective plan.

When to clean

Ash doesn’t burn, so it has to be removed from the DPF mechanically when it impedes exhaust flow, a condition indicated by a backpressure light on the dash. But most experts believe drivers shouldn’t wait for a warning light.

“With a lot of idling or local service, you’ll see shorter intervals.”

–WheelTime’s Bob Giguere

First, determine the duty cycle. “Under ideal conditions in over-the-road service, you can go 300,000 miles, but with a lot of idling or local service, you’ll see shorter intervals,” says Bob Giguere, product support manager at Inland Power Group of the WheelTime truck service network. Giguere recommends following manufacturers’ recommended intervals for DPFs operated under favorable conditions.


Dirty exhaust enters the DPF, and soot is trapped on the coated ceramic honeycomb material inside the filter, rendering the exhaust exiting the filter clean.


What’s favorable? The amount of oil consumed and engine hours are both primary factors, says Giguere. A major reason for clogging is ash from burned oil, and idling engines use more oil because the piston rings work less effectively. Idling also means poor combustion of fuel and more soot, potentially fouling the DPF.

On-/off-road and heavy-haul operations put the engine in high load conditions more often than highway vehicles. Any condition that helps maintain proper airflow into the engine or optimizes the injection system will help extend mileage and hours between cleanings by minimizing exhaust soot.

To optimize DPF cleaning intervals, pay attention to:

• Necessary overhead adjustment;

• Air cleaner replacement;

• Charge air cooler cleaning and testing, with intake air hose maintenance to minimize charge air leakage;

• Periodic turbocharger inspection; and

• Thorough injector maintenance, including adding injector cleaners and having injectors replaced or reworked as necessary.

Operate the engine at an appropriate rpm, normally at or above peak torque, when running continuously in heavily loaded full-throttle situations. “A driver needs to pay attention to an increase in the frequency of active regeneration cycles, loss of power and a decrease in fuel economy,” says Larry White, Paccar Parts business development manager.

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