How to Remove Urea Crystallization in the Exhaust Pipe?
3 Answers
Use boiling water for cleaning: When the urea solution is in a stable state, water evaporates and crystallizes. Therefore, as long as the cap of the urea tank is tightly sealed, crystallization inside the tank will be very slow. Secondly, a small amount of crystallization inside the tank is not a big issue, as the urea filter can remove impurities. During the operation of SCR vehicles, due to the special properties of the urea solution, crystallization will occur in the urea pipes and nozzles. Issues to pay attention to during the crystallization and dissolution process of automotive urea: 1. Urea pipe and cooling pipe: The purpose of shaking the urea nozzle left and right in hot water is to quickly dissolve urea crystallization. If conditions permit, the urea pipe and cooling pipe of the urea nozzle on the vehicle can also be cleaned without the need to disassemble the urea pipe and cooling pipe of the urea nozzle. 2. Assembly: After each disassembly of the urea nozzle, replace the urea nozzle gasket during the assembly process; after the urea pipe is installed, first install the solenoid valve connector, then the cooling water pipe, and finally the urea pipe.
The exhaust pipe of my diesel truck was completely covered with white urea crystals, caused by long periods of idling. I tried several methods: first, I rinsed the hardened deposits with warm water to soften them, then carefully cleaned the nozzle and pipes with a soft-bristled brush to avoid scratching the metal. After waiting for the bubbles to dissipate, I sprayed a dedicated urea cleaner and let it soak for about ten minutes before wiping it clean. The whole process took me over an hour, but the results were good. Now I’ve learned my lesson—I always use genuine urea solution, ensure the temperature is normal before driving, and let the system automatically clear soot at high speeds to prevent clogging. The key is to be patient and not rush. DIY cleaning can save repair costs, but make sure to wear gloves to protect your hands.
To remove urea crystallization from the exhaust pipe, the primary goal is to resolve clogging issues. I generally recommend first wetting the crystallized area with a water pump hose for a few minutes to soften and dissolve the urea, then gently scraping off any residue. Remember not to use metal tools, as they can easily scratch the pipes or sensors. After cleaning, use compressed air to dry the pipes to prevent rust. During regular maintenance, frequently check the urea tank level and use high-quality urea to avoid impurity buildup. If the crystallization is severe, it's best to take the vehicle to a repair shop for high-pressure equipment treatment to ensure thorough cleaning. Regularly driving long distances at highway speeds helps burn off deposits, avoiding the accumulation of issues from frequent short trips with start-stop cycles.
