Your diesel selective catalytic reduction (SCR) system is essential to maintaining your vehicle’s engine and managing emissions. Discover how to prevent diesel exhaust fluid (DEF) crystallization and keep your system clean and performing optimally, with a simple maintenance plan.
What Is a Diesel SCR System?
A diesel SCR system controls emissions by reducing the volume of nitrogen oxides that diesel engines release into the atmosphere. The system converts nitrogen oxides into nitrogen gas and water vapor via a complex chemical reaction by injecting urea-based diesel exhaust fluid into the exhaust stream.
Why SCR Systems Fail – Common Problems
Most of the time, a clean SCR system faces few challenges. If you encounter a problem, it’s usually due to the DEF system:
- Low-quality or contaminated DEF: Using low-quality diesel exhaust fluid can quickly lead to crystal buildup in the system, reducing efficiency.
- Urea crystal buildup in the system: Whether caused by a water imbalance in the tank, temperature problems or low-quality fluid, crystal buildup is one of the most common problems SCR systems face.
- Low or no diesel exhaust fluid: If your DEF warning light comes on, this is the most common cause. Refill the DEF tank to get the system back online.
- Electronic or sensor problems: Of course, the system incorporates various electrical components, any of which may malfunction and cause an SCR issue. Faulty nitrogen oxide and temperature sensors may give incorrect readings, leading to error codes.
- Clogged or failed DEF injectors: Your SCR system relies heavily on the DEF system, which injects diesel engine fluid into the exhaust stream. When an injector is faulty, it prevents the system from injecting and limits effectiveness.
These are just a few of the common SCR challenges. More severe or unusual challenges may require professional diagnosis with an OBD II tester. You can solve most of these challenges with regular cleaning and maintenance, except for electrical concerns.
How to Clean a Diesel SCR System
Cleaning an SCR system is easy, depending on the problem. Is it a DEF crystallization problem, or is your system contaminated?
If your DEF system is contaminated, you’ll need professional assistance. A technician needs to drain, purge and refill the system, as this process is the only way to remove these contaminants.
However, if your system suffers from a buildup of urea crystallization, it’s relatively easy to repair. A high-quality SCR system cleaning solution like Premium DEFender™ solves multiple problems simultaneously, offering a solution to:
- Clogged DEF injectors: This product eliminates crystal deposits from clogged injectors, facilitating function and allowing the injectors to operate optimally by restoring the nozzle spray pattern.
- Standard trouble codes: By eliminating crystal deposits and returning flow patterns to their optimal function, Premium DEFender clears many error codes related to DEF malfunctions.
- General crystal buildup: This comprehensive product eliminates all crystal deposits systemwide, restoring the system’s function to pre-buildup condition.
To use the product, fill the DEF tank, adding Premium DEFender at a rate of one ounce per 2.5 gallons of diesel engine fluid. Then, drive the vehicle at a steady pace. If it has a regeneration cycle, that works too. Either way, ensure consistent flow through the system so the cleaner can remove crystal buildup.
Tips for Preventing DEF Crystallization and SCR Issues
Diesel exhaust fluid is a precise blend of water and liquid urea. When the water evaporates, the ratio is out of balance, and urea crystals may build up in the system components, hindering successful emission management and reducing overall efficiency.
DEF crystallization prevention is simple, as long as you adhere to a few basic guidelines, specifically:
Choose a Quality Diesel Exhaust Fluid
When you refill your diesel exhaust fluid tank, ensure two things. First, always use a premium fluid with a trusted reputation, since lower-quality DEF leads to faster crystallization.
Second, thoroughly clean the tank cap and the area around it before pouring the fluid into the tank. This approach prevents the fluid from being contaminated with dust and debris, promoting better, more consistent performance.
Store DEF Properly
To keep your DEF fluid viable and get the best results, ensure it’s stored properly. Store it out of direct sunlight, preferably in a space that maintains a temperature of 12-86°F. Heat is the biggest problem for DEF since it may degrade the liquid or cause evaporation, making the urea more concentrated and leading to crystallization.
Practice Consistent Maintenance
As with any other part of your vehicle, a routine maintenance schedule is essential to your SCR system’s performance. Fill the DEF tank regularly and adhere to the vehicle manufacturer’s instructions for other maintenance aspects. Even a clogged or dirty filter can have a significant impact.
Use Trustworthy Cleaners and Additives
Additives are integral to maintaining your DEF and SCR systems. Choosing the right solution for your system keeps it lubricated and clean, prevents crystallization and improves system performance. The most important thing is to select a trustworthy product that gets consistent positive reviews and offers proven efficiency.
Long-Term Benefits of SCR Maintenance
Keeping your SCR system clean offers some significant long-term benefits, including:
- Extended system lifespans: Practicing diesel exhaust aftertreatment and maintenance extends your system’s lifespan and, by extension, your vehicle’s serviceable life.
- Better fuel efficiency: While not a primary goal of either system, these functions improve engine efficiency enough that the vehicle uses less fuel. Some truckers report a three to five percent fuel reduction.
- Lower carbon emissions: Monitoring emissions is essential when driving a diesel vehicle. A functional DEF system reduces emissions through complex chemical reactions, lowering overall emissions.
- Optimal engine performance: When your SCR and DEF systems operate optimally, they improve your vehicle’s engine performance, giving it more power.
- Regulation compliance: An SCR system that functions at its best keeps your vehicle’s emissions within acceptable ranges, ensuring legal compliance. Malfunctioning systems may produce more emissions, leading to failed emissions tests and fines or penalties.
Whether you want your vehicle to function optimally or to be more sustainable, regular maintenance offers some significant benefits.
FAQs About SCR System Care
Learn more about caring for your SCR system with some of our FAQs.
How do I maintain an SCR system?
Keep the diesel exhaust fluid tank full and clean to maintain your SCR system. Use premium-quality DEF fluid and monitor it regularly for problems like urea crystal buildup or system leaks.
Can a diesel SCR be cleaned?
Yes, you can clean an SCR system. To help remove crystal deposits, add a dedicated cleaner like Premium DEFender to the mostly full DEF tank. This DEF injector clogging fix prevents and eliminates crystallization buildup systemwide while providing lubricity for DEF system components.
Can I drive with an SCR fault?
While you can drive with an SCR fault — for a short while, at least — we don’t recommend it. This issue may cause problems like reduced performance, enter into “limp mode” before complete engine shutdown. It is far better to take the vehicle to an experienced, qualified technician quickly.
Simplify Diesel SCR Maintenance With Hot Shot’s Secret
At Hot Shot’s Secret, our SCR system cleaning solution eliminates urea crystal buildup, protects the injector and sending tank, and lubricates the entire SCR system. Safe for use in any system, it lowers the DEF’s freezing point by around 20°F and reduces downtime or expensive repairs.
Maintain and clean your SCR system with Premium DEFender, an all-in-one DEF maintenance and protection solution. Our specially formulated products can help you maintain your vehicle’s DEF system, boost performance and extend your vehicle’s lifespan.