Clean Diesel – Diesel Technology

Diesel Particulate Filters: Blessing and Curse

January 2015, - Feature

by Tom Berg - Also by this author

Diesel particulate filters help cleanse exhaust and give us cleaner air to breathe, but they cause frequent grief and expense.
Diesel particulate filters help cleanse exhaust and give us cleaner air to breathe, but they cause frequent grief and expense.

Diesel particulate filters are one of the major additions to exhaust systems in recent years, and they are a blessing and a curse. Used since 2007 to meet EPA regulations, DPFs strip soot and ash from the exhaust stream. Added to exhaust-gas recirculation already used to reduce nitrogen oxides, DPFs greatly cleansed exhaust and eliminated the characteristic diesel smell. Addition of urea injection in 2010 and advancements in combustion efficiency along the way result in exhaust so clean that it can barely be measured.

That’s the blessing. The curse comes from the extra maintenance and repairs required to keep the systems operating, along with unscheduled downtime, stranded drivers and missed deliveries, fleet managers say.

DPFs replaced simple mufflers, and are rather complex and expensive pieces of equipment. A DPF consists of a stainless steel cylinder holding the ceramic honeycomb filter, which snatches particulates — soot — produced by engine combustion and stores them until cleaning takes place. Heat and pressure sensors tell an engine’s electronic controls if the DPF is working properly, and warn when it’s not. Cleaning with exhaust heat alone is called a passive regeneration; if that’s not sufficient, active or forced regenerations occur periodically.

Heat for an active regen is created by adding fuel to exhaust gasses, and the fuel — sometimes called “hydrocarbons” — is ignited just ahead of the DPF. Temperatures of up to 1,100 degrees Fahrenheit result, burning out the soot. When a dash light warns a driver that a regen is needed, he must pull over soon and let it happen. If he doesn’t, electronic controls, which know via sensors that the DPF is plugged up, will cut engine power and eventually shut it down. The engine fast-idles during an active regen, so the truck must remain parked. Heat from the tail pipe can ignite grass below or overhead tree branches, so drivers need to park the truck away from such flammable objects.

A new DPF costs about $5,000, and a reconditioned one about half that. A recon unit works almost as well as a new one, and suppliers have exchange programs where a dirty DPF plus a service charge is traded for a cleaned one. Or the truck’s owner can wait for his own DPF to be serviced so it stays with the truck. A damaged DPF has almost no value and the owner must buy another. The ceramic honeycomb structure can suffer cracks from road shock or accidental dropping, or melted by excessive heat. If neglected, it can get so badly plugged up with soot that it can’t be cleaned.

Reliable Carriers bought an SPX portable DPF cleaner for about $10,000, and it’s paid for itself in saved cleaning fees. 
Reliable Carriers bought an SPX portable DPF cleaner for about $10,000, and it’s paid for itself in saved cleaning fees.

Sometimes DPFs are affected by other systems on the truck. Kevin Tomlinson, maintenance director at South Shore Transportation in Sandusky, Ohio, shared such an experience in a recent HDT webinar: “The DPF on a truck I had just changed out last week with an exchange unit is regening, and went into shutdown this morning… 60 miles from the closest dealer. We had to have it towed in to the dealer. It turns out that fuel pressure wasn’t enough to support regening.” A forced regen shouldn’t be needed for hundreds of miles after a fresh DPF has been installed, and in this case the faulty fuel system added to the problem.

A DPF also collects ash from combusted motor oil, and it remains in the filter until it’s serviced. Ash is blown out by high-pressure air for most DPFs, or rinsed out with de-ionized water in the case of one engine builder’s DPFs. Special machines accomplish this, and require the DPF, which weighs about a hundred pounds, to be removed and placed on or in the machine for cleaning. Some fleets have bought their own machines.
Many fleet managers now schedule DPF cleaning as part of regular preventive maintenance procedures.

Larger console-type cleaners are sold by manufacturers, such as the one from FSX at right.
Larger console-type cleaners are sold by manufacturers, such as the one from FSX at right.

John Sullivan, director of maintenance at Reliable Carriers in Canton, Mich., bought a portable device that can be moved close to the truck being serviced.

“You have to pull the DPF and insert it into the cleaner,” he explains. “It uses shop air and runs automatically. It’s pretty easy. I paid $10,000 for it. It has paid for itself. [Removal to reinstallation] of the DPF is four hours or less.”

Jamin Woody, service manager at Motor Trucks, a Navistar dealer in Everett, Washington, prefers the more complex and expensive system his facility has used since 2010. He tested it against a portable one and found that based on restriction readings, his system removed much more ash.

“From our experience, the cleaner that filter gets when you clean it, the longer it will last in filter lifetime, and the fewer issues you will have upon reinstallation.”

– Editor In Chief Deborah Lockridge contributed to this article.


  1. 1. Phred [ January 26, 2015 @ 10:59AM ]

    ESW Group's Thermacat filters have no downtime and regenerate automatically. What's the problem?

  2. 2. Bud Caldwell [ January 28, 2015 @ 01:22PM ]

    A $5000. DPF, where?
    Temperatures up 11oo degrees, that should read 2000 plus degrees.
    Clean exhaust with addition of DEF. How about the burning of the DEF
    creates methane, the greenhouse gas AB32 was designed to stop, and
    now it's a part of a diesel engines exhaust stream that was previously
    non existant.
    Dpf's create problems in engines. Let's look at CARB's own DPF Maint.
    Guide. Inspect turbo's daily. That will take five hours per day, no decent
    trucker should have a problem with that, should they?
    It looks like the author was fed just enough mis information to make this
    believable to a non trucker.
    Really, a $5000 DPF and someone would be stupid enough to just pick
    the last guys freshly baked DPF in trade, You Bet!

  3. 3. Tony Hobbs [ January 29, 2015 @ 07:25AM ]

    So true Bud Caldwell.$16,000.00 To $20,000.00 for instalation of filter.and each truck is data logged for a certain filter for that engine. (exchange program Ha Ha).These filters are dangerous and are not cost effective.

  4. 4. Hank de Carbonel [ February 03, 2015 @ 12:44PM ]

    I think your article raises more questions than it answers. I assume we are talking about class 7 & 8 diesel trucks.? I believe a passive filter would better be described as operating without any active participation of the driver, the active requires the truck be stopped and regeneration instigated.The "hydrocarbons" aka Diesel Exhaust Fluid. Only active would require parking.
    A new retrofit DPF costs between $15,000 and $20,000 or more depending on data logging and application.The filter element may cost between $5000 and $7500.00 and in California exchange is not permitted except in very rare cases. Blowing ash out with high pressure ash must be done in a contained area because the ash is considered a hazardous waste. Unless you are sure ,using water will shorten if not destroy the element. The element is cleaned in the cleaner not the entire DPF. Depending on how plugged up the element it may take "cleaning" in a Kiln for approximately 8 hours. Then the element can be evaluated for reuse.

  5. 5. Adam [ February 07, 2015 @ 03:26PM ]

    I don't know where you folks are getting your service done or what engines your running, but our (Fleet) price on a recon DPF from Cummins is under $1000 for the 2013 trucks we run. It takes two or three hours to swap one out and blow out the DOC. As far as temperatures, anything over 1400 is a problem. 1100 is more common. And DEF is not hydrocarbon, it's 32% urea and the rest water. The hydrocarbon referenced in the article is fuel. A separate injector located after the turbo injects fuel into the exhaust, when it hits the hot catalyst ahead of the DPF it ignites and creates the heat needed to turn the soot into ash. DPFs aren't evil, they just take a little more knowledge and better maintenance practices then you can learn reading the comments section in an internet article

  6. 6. Anthony Bulygo [ May 05, 2015 @ 11:36AM ]

    Missing is a critical issue. As stated, the ash removed from the DPF is considered a Hazardous Material. Hazardous because the particles of ash are so small that they can be absorbed through the skin and if inhaled can be attached to the linings of the lung and not expelled. If you have coolant entering the DPF during a major engine failure, the water in the coolant will chemically change the ash to a concentrated acid that can severely injure the mechanic. Be careful out there and use your protective gear. when servicing the units. ALL ASH MUST be captured and held for HazMat pickup. So, if you think you can just remove it and blow it out with the air hose at the shop, reconsider the consequences. Be safe. And, yes, the EPA mandates that the DPF registered to the vehicle MUST remain with the vehicle for life. No exchanges, except for totally failed units. Application must be made to the EPA here in CA for DPF Serial Number changes.

  7. 7. Michael Galorath [ June 11, 2015 @ 12:37PM ]

    Lets face it. The EPA shoved another product down the throat of the consumer. Not fully tested in real world conditions. Just like adding more alcohol to gasoline. The DPF/DEF process will evolve into something better down the road. One thing for sure the DEF/DEF systems will eliminate the single interdependent trucker by pricing the maintenance of a vehicle out of reach. Or we will see more very old vehicles running around the country except in California

  8. 8. Eric Hahn [ July 10, 2015 @ 02:25PM ]

    This brings the change to the front door and cleaner alternatives will be considered in many of my future applications.

  9. 9. Jim Barfield [ July 28, 2015 @ 12:28PM ]

    I work for Monster DPF. Our most expensive DPF regenerated filter runs $2,095. Most are a couple of hundred dollars less. They can go several years on average between service, and we deliver the part to the service center where the truck is located in 24 hours or less. Yes, they are a hassle for the driver to replace -but then again you should see what comes out of them- and a lot of that is particulate that would be in the driver's air. It is true we cannot *sell* them in California- but many drivers just have the service done in Arizona or Nevada, Washington state, etc. The trapped particulates that we burn out of them are extremely fine particles and really bad on the lungs...

  10. 10. Gans [ August 29, 2015 @ 06:17AM ]

    We should use fuel only when we are nessary and we should use cycle.

  11. 11. Stu [ June 20, 2016 @ 02:18AM ]

    A simple fact is that a DPF is designed to trap the semi combusted nasty stuff (soot) and the nasty stuff is converted to less nasty stuff by performing a 'regeneration' to fully combust it and turn it in to ash. The ash fills up the DPF over time and so it has to be regularly removed to be cleaned, otherwise it will hinder the performance of the exhaust, cause the DPF to constantly regenerate, all of which results in higher fuel consumption and the eventual costly premature replacement of the DPF. The answer? get it blown clean as a matter of routine every time the vehicle is serviced. That way no extra downtime, no nasty surprises and the problem is gone. $200 per year for peace of mind and DPF will last until you replacement the truck for new. Question is do your Truck service providers have a DPF cleaning machine on site to offer this service?

  12. 12. C. H. Robinson [ August 11, 2016 @ 06:44AM ]

    Appreciate the 11 comments. Appreciate too the simple explanations and the real costs incurred based on real time scenarios. Have a 2015 Mack and it appears to have a top of the line DPF system, based on the remarks above. Agree with the statements that so many "fixes", like ELD's, are developed without consideration of real world consequences. In the case of rushing the ELD's to market, it is based on the billions of dollars that the forced installation of these devices will generate for Omnitracs and others. Safe emissions everyone can support. ELD's do nothing for safety; they actually are creating more pressure on drivers to push and take away the incentive and the ability to be flexible with the constantly changing conditions inherent in professional trucking.

  13. 13. Tim [ January 06, 2017 @ 07:45AM ]

    When I initiate parked regen, the rpms increase for about an hour and a half, but no HEST lamp illuminates. Does this mean its not functioning? 2007 kenworth plow truck.

  14. 14. perry morgan [ June 20, 2017 @ 12:03PM ]

    besides all of the problems mentioned above with the DPF's like fires caused by to added heat, ( the fires cause know carcinogens to be emitted into the air, and DEF which is 35% urine and once heated becomes ammonia which means our kids are breathing both ammonia and urine partials) but I do not see where any government agency has taken into consideration that the loss of fuel mileage that these filters have caused has had an effect on our environment. 1. More oil will need to be imported which causes more pollution. 2. More oil will need to be refined which causes more pollution. 3. More fuel will need to be transported to the retail fuel stations which cause pollution. 4. Vehicles will need to exit the highways more often to refuel which cause more pollution. 5. Engines have a much shorter life ( about 50%) do to the DPF's which cause more pollution. There is also many ,many more ways that these DPF's are causing added pollution but our government does not take any of this into consideration. It is no different than a gambler who tells you about the times that he has won at gambling, but always leaves out the many more times that he has lost!!! the only difference is that it is us, the average citizen that is losing and it is the government that is winning by creating more government jobs and putting more of a burden on the small business man.


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