In the world of trucking, aftertreatment systems have become as crucial as the engine itself. These systems, designed to meet emissions standards, keep our roads cleaner but can also bring trucks to a halt when things go south. Let’s dig into the five most common aftertreatment failures causing breakdowns and how to handle them.
1. Diesel Particulate Filter (DPF) Clogs
The Diesel Particulate Filter (DPF) plays a critical role by trapping soot and carbon emissions. Over time, though, these filters become clogged, especially if DPF regeneration (the process of burning off trapped particulates) doesn’t work as intended. Causes of DPF clogs often include extended idling, low-quality fuel, or short trips that don’t allow full regeneration cycles.
Signs of a Clogged DPF:
- Reduced engine performance and power.
- Increased fuel consumption.
- Check Engine or DPF warning lights.
Prevention Tips: Regular forced regeneration (a manual override of the system's regeneration) and using high-quality diesel fuel can minimize DPF clogging. Monitoring the DPF system is essential, as ignoring it can cause back pressure in the engine, leading to more severe engine issues.
2. Selective Catalytic Reduction (SCR) System Failures
The SCR system lowers nitrogen oxide (NOx) emissions by injecting Diesel Exhaust Fluid (DEF) into the exhaust stream, converting NOx into harmless nitrogen and water. However, SCR systems are sensitive, and even slight contaminants in the DEF tank can disrupt the entire process.
Common Causes of SCR Issues:
- Low or contaminated DEF levels.
- DEF injector failures.
- Poor quality DEF fluid.
Signs of SCR Failure:
- DEF warning light.
- Reduced fuel efficiency.
- Increased exhaust smoke.
Prevention Tips: Always use high-purity, certified DEF to avoid contamination. Cleaning the SCR injectors regularly is also beneficial, as clogged or damaged injectors can lead to an expensive replacement down the line.
3. Exhaust Gas Recirculation (EGR) Valve Malfunctions
The Exhaust Gas Recirculation (EGR) valve controls the amount of exhaust gas re-entering the engine, effectively lowering combustion temperatures to reduce NOx emissions. However, diesel exhaust can be a tough environment, leading to carbon build-up in the EGR valve. When this happens, it disrupts the valve’s functionality, causing poor engine performance and, eventually, failure.
Symptoms of EGR Valve Failure:
- Rough idling or stalling.
- Loss of engine power.
- Reduced fuel efficiency.
Prevention Tips: Regularly clean or replace the EGR valve to prevent carbon buildup. For drivers facing frequent EGR issues, EGR cooler cleaning services are worthwhile to ensure the system runs smoothly. Ignoring EGR failures often worsens emissions, affecting both engine health and compliance with emissions standards.
4. Diesel Oxidation Catalyst (DOC) Failures
The Diesel Oxidation Catalyst (DOC) reduces harmful exhaust pollutants like carbon monoxide and hydrocarbons by converting them into water and carbon dioxide. However, the DOC can become contaminated or plugged, especially if the engine is leaking coolant or oil.
Signs of DOC Problems:
- Loss of engine performance.
- Abnormal smells from exhaust.
- Reduced DPF lifespan due to inefficient DOC.
Prevention Tips: Maintaining a regular preventive maintenance schedule is essential to catch any oil or coolant leaks before they reach the DOC. Ensure that your engine’s oil and coolant levels stay within recommended levels to prevent DOC contamination and extend the lifespan of your DPF and other aftertreatment components.
5. Diesel Exhaust Fluid (DEF) Dosing Module Issues
The DEF dosing module is the system that injects DEF into the SCR catalyst. If it fails, DEF won’t reach the exhaust system, which means no NOx reduction. DEF crystallization, often due to low-quality DEF or improper storage, is a major issue. Temperature swings can also make DEF freeze or crystallize, blocking the system.
Signs of DEF Dosing Module Problems:
- Frequent DEF alerts.
- Decreased fuel efficiency.
- Noticeable power loss.
Prevention Tips: Store DEF in temperature-controlled environments and inspect it regularly. If you notice crystallization, immediately flush the system to prevent buildup. Use only high-grade DEF to reduce crystallization and prevent clogs, especially in colder climates where DEF tends to freeze.
Preventive Measures to Keep Aftertreatment Systems Running Smoothly
While aftertreatment systems are complex and expensive to repair, regular maintenance makes a difference. Here’s how to keep these systems running smoothly:
- Regular Regeneration Cycles: Following a consistent schedule for DPF regeneration minimizes clogging.
- Use High-Quality DEF and Diesel: Higher-quality fluids and fuels prevent contaminants and reduce wear on filters and injectors.
- Routine Cleaning and Inspections: Keeping the DPF, DOC, and SCR systems free of soot and debris extends their lifespan.
- Monitoring System Health: Many trucks have sensors to alert drivers about emissions issues—don’t ignore these signals, as early detection can prevent breakdowns.
Final Thoughts
Aftertreatment systems are key to reducing emissions and improving air quality, but they also bring new challenges for diesel trucks. By understanding the signs of common failures and how to prevent them, drivers and fleet managers can keep their rigs running smoother and longer on the road. Whether it's DPF clogs or SCR failures, preventive maintenance and high-quality fluid choices make a world of difference.
If you’re facing aftertreatment issues in Omaha, NE, or simply want a thorough inspection to avoid these problems, Impact Diesel Repair is here to help!
