Where is the urea added in large vehicles?

[Luke]

Automotive urea is filled into a dedicated urea storage tank, which is located near the fuel tank. Since nitrogen oxides can be catalytically reduced by ammonia from urea hydrolysis at high temperatures into harmless nitrogen and water, which are then discharged, China's National IV emission standards implemented in 2008 mandated the use of automotive urea in the emission reduction systems of diesel vehicles. The primary reason for adding urea to diesel vehicles is to reduce exhaust emissions, as the exhaust from diesel engines mainly consists of nitrogen oxides and carbon particles. If a truck lacks urea, its nitrogen oxide emissions can be even worse than those of National III vehicles. Prolonged absence of urea circulation can easily lead to crystallization blockages or high-temperature damage in the urea pump nozzle, pipelines, and urea pump, resulting in insufficient vehicle power and difficulty in starting. Nitrogen oxides in diesel engines are predominantly nitric oxide. Excessive nitric oxide concentration can affect human thoracic and pulmonary functions as well as central nervous system disorders. Additionally, nitric oxide in the air gradually converts into nitrogen dioxide, which has a strong irritating odor and can cause respiratory system diseases in humans.

[McIker]

As a long-haul truck driver who frequently covers long distances, I know the location of the urea filler port all too well. The vast majority of heavy-duty trucks place it on the right side of the vehicle, either behind the fuel tank or right next to it. For example, on my FAW J6P, you can spot the blue-labeled urea cap by crouching in front of the right rear wheel. European trucks like Scania are more user-friendly, positioning the AdBlue filler port directly alongside the diesel filler on the right rear side, clearly marked with "AdBlue"—allowing you to refill both fluids without turning the truck around. Always look for the blue marker or funnel symbol to avoid mistakenly filling the diesel tank. When refilling, make sure to insert the dedicated hose all the way down, otherwise urea crystallization can clog the pipes. Some newer models have relocated the port to the left side of the chassis, so it's best to walk around the truck and check before loading cargo. Just feel along the chassis for that blue plastic cap, and you'll find it.

[MacPresley]

When I was doing maintenance work in the fleet, I had to refill urea for over a dozen vehicles every day. Diesel trucks generally have three common urea tank locations: The most common is behind or on the side of the fuel tank, usually slightly smaller than the fuel tank; the second is near the driveshaft in the middle of the chassis, which requires bending down to see; a few imported trucks place it beside the left frame rail. My suggestion is to open the door and squat down to look for the blue plastic cap about 10cm in diameter on the chassis (new national standards mandate blue identification). For special chassis like refrigerated trucks, the urea tank might be inside the tool compartment. Important reminder: The engine must be turned off for three minutes before refilling, otherwise it will trigger system alarms. Also, in northern winters, remember to switch to -35°C antifreeze urea in advance. Last year, a Sinotruk Howo truck had its pipes cracked by frozen regular urea, costing over 8,000 yuan in repairs.

[VanAubrey]

Novice truck drivers often struggle to locate the DEF (Diesel Exhaust Fluid) filler port. Actually, designers usually prioritize operational convenience. Take domestic heavy-duty trucks like Dongfeng Tianlong for example - the DEF tank is installed on the same side as the diesel tank, positioned about half a meter further back with a distinctive blue cap. European trucks such as Volvo FMX are marked with bold "AdBlue" lettering. Special attention is required for flatbed semi-trailers where it might be behind the fifth wheel, while dump trucks often position it diagonally behind the cab. Here's a practical tip: follow the blue hose along the right side of the frame - it leads directly to the DEF tank. Sensor wiring makes identification even easier. Always keep a long funnel handy during refills to prevent crystallization from spills. Particularly in summer, don't wait for the dashboard warning light - replenish when there's about 10% remaining.