What is the reason for the absence of urea reflux sound after engine shutdown?

[VanAliyah]

After engine shutdown, the absence of urea reflux sound may be caused by a malfunction in the urea recovery device, and it should be inspected and repaired at a 4S shop as soon as possible. Below is relevant information about automotive urea: 1. The role of automotive urea: Generally, adding urea to vehicles is primarily to reduce exhaust emissions, as diesel engine exhaust mainly consists of nitrogen oxides and carbon particles. 2. National regulations: Because vehicle exhaust emissions pose significant harm to both people and the environment. Therefore, the National IV standard implemented in 2008 in China stipulates that diesel vehicles must use automotive urea in their emission reduction systems.

[Martha]

I've been driving diesel vehicles for over twenty years, and I know there should be that 'gurgling' sound after turning off the engine, indicating the urea pump is recirculating excess fluid. If there's no sound, it's a pretty common issue. Most of the time, it's a problem with the pump itself, like a seized motor or internal freezing/scale buildup. Once, my car had this issue, and it turned out the urea froze in low winter temperatures, blocking the pipes—just blowing some warm air fixed it. It could also be incorrect sensor signals causing the pump not to work. I suggest first checking if the urea level is sufficient; if it's too low, the system will shut down. Then, see if there's any fault code on the dashboard. If left unfixed, over time, the urea system may fail, and the engine might go into torque reduction mode, making the car sluggish and fuel-inefficient. Before parking, try pressing the brake pedal a few times to force the system to activate. If there's still no sound, it's best to get a full check at a 4S shop for the pump and wiring. Small issues might cost a few hundred bucks, but delaying could make it more expensive.

[McSawyer]

Hey, as a guy who's worked on plenty of urea systems, I can tell you that the return flow sound is like a car letting out a relieved sigh after sneezing. No sound? Chances are the pump's busted—common issues like corroded/loose wire connections or worn/stuck pump cores. I once had a vehicle that went dead silent after shutdown, and testing revealed it just needed a new relay. The urea system relies on pump pressure to circulate fluid, so return flow during pump shutdown is a normal protective mechanism; silence could mean clogged lines or air pockets—check if the urea filter and injector are clean. Don't panic, try restarting the vehicle a few times to let the system run self-checks. Left unfixed, not only will the fault light come on causing excess emissions, but long-term DPF damage may occur. Remember to maintain regular urea fluid changes to prevent crystal buildup, and you'll be golden.

[Kevin]

As an environmental volunteer, I'm concerned about vehicle emissions. The absence of urea reflux sound after engine shutdown is problematic—it indicates the selective catalytic system isn't properly closing, affecting nitrogen oxide purification. Common causes include pump control module failure, low-temperature liquid solidification, or circuit short circuits. During a public welfare inspection, I encountered a similar case caused by insufficient internal pump pressure. Untimely repairs can increase emissions, pollute the environment, and may trigger traffic restriction fines. Simple advice: ensure proper urea concentration to reduce crystallization and check basic wiring connections. Safety first—don't overlook this small signal.