What Causes Antifreeze in the Urea Tank?
2 Answers
Urea tank contains antifreeze due to the presence of heating devices and external low temperatures. Heating Devices: The urea tank is equipped with a urea temperature sensor and a urea heating device. The post-processing system and some pipelines are also fitted with heating electromagnetic coils or solenoid valves. When the urea temperature is detected to be below 0°C, the solenoid valve automatically opens to introduce coolant to heat the urea until it reaches 7°C, at which point it stops working. External Low Temperatures: In northern or cold regions, freezing at temperatures below -11°C is quite normal. Simply start the engine for preheating. At this time, the system may report a blockage fault, which can be ignored. After preheating for a while, turn off the engine and restart it, and it will return to normal. There is no need to worry about the urea pump or pipelines freezing and blocking, as long as no improper operations are performed. The final step of the post-processing system is the system draining process, which automatically removes residual urea solution from the system and pipelines to prevent crystallization (freezing).
I've dealt with many vehicle issues before, and finding antifreeze in the urea tank is usually due to accidental mixing. The most common scenario is when owners or mechanics confuse the two fluids during refilling—antifreeze is often red, while urea solution is typically a clear blue liquid, but relying on color alone can lead to mistakes. Additionally, if vehicle pipes age or leak and the antifreeze system is close to the urea tank, it may seep through gaps. This causes major trouble: urea is used in the emissions system, and mixing it with antifreeze can form crystals that clog nozzles, corrode pipes, trigger engine warning lights, reduce power, and affect environmental compliance. I recommend driving to a professional repair shop ASAP for inspection and cleaning—don’t attempt DIY fixes to avoid worsening the damage. For prevention, always distinguish refill port locations, check manual labels, and maintain pipes regularly to prevent leaks. Timely action saves money and ensures safety.
