Diesel engines are notorious for accumulating carbon deposits. This carbon buildup comes from the incomplete combustion of fuel inside the cylinders. Over time, these deposits can restrict airflow, reduce performance and fuel economy, increase emissions and even cause catastrophic engine damage if left unchecked.
The good news is that most diesel engines have specialized components designed to continually clean out carbon as part of normal operation. In this comprehensive guide, as a professional diesel engine parts supplier, we’ll explore the leading parts and systems that keep diesel motors clean, including:
- Diesel Oxidation Catalyst
- Diesel Particulate Filter
- Exhaust Gas Recirculation System
- Crankcase Ventilation System
- Turbochargers
- Fuel Injectors
Understanding what each of these critical systems does, how they remove carbon, and how to keep them functioning properly will give you the best chance at minimizing deposits and maximizing the life of your diesel vehicle. Let’s dive in!
What Causes Carbon Buildup in Diesels
But first, what causes heavy carbon buildup in the first place? There are three primary culprits:
1. The Combustion Process
Diesel combustion produces more particulate matter and less complete burning compared to gasoline engines. As a result, excess carbon makes its way into key engine components.
2. Engine Design
Modern emission-reduction equipment like EGR and DPF systems decrease tailpipe pollution but have the side effect of increased carbon internally.
3. Oil Consumption
If your engine burns oil (from worn parts or faulty seals), that oil ash also contributes to carbon deposits down the line.
The result is thick, hard carbon layers in places like:
- Combustion chamber
- Pistons
- Intake valves
- Exhaust valves
- EGR system
- Turbocharger
Fortunately, most diesel vehicles have specialized cleaning systems in place to continually scrub away these deposits during normal driving.
What Part Cleans Out Carbon in a Diesel Engine?
Diesel Oxidation Catalyst
One line of defense against carbon buildup is the diesel oxidation catalyst (DOC). This stainless steel container sits in the exhaust stream:
DOCs utilize a chemical process to break down pollutants into less harmful components before emission out the tailpipe.
As particulate matter like soot and unburnt fuel passes through, the catalyst triggers an oxidizing reaction that burns off most of these particles, cleaning the exhaust—along with preventing some buildup downstream around valves and in the DPF filter.
DOCs are maintenance-free and can last over 100,000 miles before needing replacement. But you can maximize their cleaning power by:
- Using manufacturer-recommended diesel fuel to decrease contaminants
- Driving frequently and at consistent speeds to keep the catalyst hot
Diesel Particulate Filter
DOCs are great at preventing carbon from exiting your tailpipe. But they don’t trap all of those microscopic particles.
That’s where diesel particulate filters come in. DPFs are usually made from ceramic or sintered metal designed to catch and store leftover soot and particulates.
They’re also located in the exhaust system downstream from the combustion catalyst:
DPFs include tiny pores and passageways measured in microns. These holes are large enough for exhaust gases to escape normally—but too small for most carcinogenic particles, forcing them to become trapped in the filter medium.
Over time, this process causes significant soot buildup inside the DPF unit. If left unaddressed, it would eventually plug and fail.
So vehicle engineers added a way for the filter to essentially clean itself called “regeneration”. By raising exhaust temperatures using extra fuel, carbon inside the DPF unit burns away into less harmful gasses. The vehicle computer triggers the regeneration cycle when sensors detect sufficient pressure from trapped particles.
Straightforward preventative steps can minimize both soot buildup and necessary regens, including:
- Limit short trips to allow adequate exhaust heating
- Address fuel, air, or oil leaks immediately
- Consider lower viscosity oil to reduce consumption
By properly maintaining your DPF system, you keep diesel particulates from exiting the tailpipe and lower the amount that gets dislodged into internal engine areas.
Exhaust Gas Recirculation System
While the goal is to eliminate airborne carbon altogether before it exits the tailpipe, some small percentage inevitably gets recirculated back into the engine.
This occurs through a technology called exhaust gas recirculation, or EGR.
Here’s a simple EGR diagram highlighting its key function:
EGR systems route a metered portion of an engine’s exhaust gas back into the intake and combustion chambers. Adding inert gasses lowers peak combustion temperatures, thereby reducing NOx emissions.
However, it also allows some particulate matter to reenter the cylinder. Just a small amount of recirculated carbon can bind to intake components.
Thankfully, due to advancing technology, most diesel EGR systems now utilize cooling. This condensation process causes heavier particulates to drop out of the gas flow, preventing at least some carbon transfer:
You can further minimize EGR gunking with simple maintenance like: – Regular fuel filter changes to avoid flow contamination – Keeping intake connections tightly fastened – Using a fuel system cleaner regularly
Crankcase Ventilation System
Oil control rings inside engine cylinders work to prevent lubricant from entering the combustion chamber.
But invariably, small amounts of oil vapor sneak by piston rings with blow-by gasses. If left unvented, these can condense on internal surfaces and promote carbon deposits in areas like the intake and valves.
Crankcase ventilation serves to remove these oil fumes. In simple terms, it takes vapors collecting inside the engine crankcase caused by blow-by and reroutes them into the intake to be consumed during normal combustion.
Here is a diagram of a basic crankcase ventilation setup:
Modern positive crankcase ventilation (PCV) valves meter the flow of these gases to ensure optimal consumption while preventing oil loss. Maintaining this delicate balance is key to managing deposits.
You can keep your crankcase ventilation cleaning properly with:
- Regular PCV valve changes
- Using the right weight oil for your climate
- Fixing external oil leaks promptly
Turbochargers
Turbochargers are excellent for increasing engine efficiency. But their location directly in the exhaust flow means they’re also vulnerable to carbon buildup.
As particulate matter exits the cylinders after combustion, the exhaust spins an internal turbine that draws extra air into the intake via a coupled compressor. This denser air allows more fuel for boosted performance.
However, these faster spinning components experience higher exhaust temps. Over time, the increased heat bakes carbon deposits on surfaces like the turbo impeller fins and bearing housing. Too much buildup can reduce performance or even lead to catastrophic turbo failure.
Thankfully, there are a few ways to reduce turbo coking:
- Allow proper turbo cool down time before shutting off your engine after driving hard
- Use only manufacturer-recommended oil. Keeping levels correct avoids coking from oil leaks
- Consider an occasional fuel system cleaning containing detergents
Fuel Injectors
Last but certainly not least on our diesel cleaning component tour are the high pressure fuel injectors themselves.
These precision machined nozzles have the crucial task of spraying metered quantities of fuel into the combustion chamber at exactly the right instant.
Dirty injectors simply can’t maintain this atomization accuracy due to internal obstruction:
Carbon deposits inside the injector tip disrupt the pressure and flow path, causing droplet formation problems. This uneven fuel delivery leads to decreased power, poor mileage, rough running, and even misfires.
While many additives claim to clean injectors, physical removal is sometimes needed for a thorough job on heavily coked units. Regardless, you can minimize the risk with:
- Using high-quality diesel fuel containing adequate detergent additives
- Consider trying an aftermarket fuel injector cleaner regularly
Conclusion
Maintaining low carbon levels requires keeping ALL these systems running properly. But now that you know diesel engines have specialized components designed to continually clean as you drive, you can help the process through simple maintenance steps.
The key systems and parts that keep diesel motors clean include:
- Diesel oxidation catalysts
- Diesel particulate filters
- Cooled exhaust gas recirculation
- Closed crankcase ventilation
- Properly functioning turbochargers
- Injector detergent use
Remember, the cleaning process isn’t isolated to one component. Implementing these best practices across the board gives your engine the best shot at reaching maximum mileage with minimal carbon issues.
Now that you know what part cleans out carbon in a diesel engine, you can keep your vehicle’s specialized cleaning systems working properly. Doing so will pay back huge dividends in performance and longevity that keeps you on the road.