Washer fluid container

A windscreen washer reservoir stores the washer fluid and, together with washer pumps, sealing grommets, level sensors, hoses, non-return valves and washer nozzles, forms a crucial part of the windscreen wiper system. On MAN and Mercedes trucks, buses and vans, sufficient and correctly metered washer fluid is essential for removing dirt, salt film and insect residue from the windscreen. A leaking, cracked or incorrectly fitted reservoir not only leads to fluid loss, but can also cause faults in pumps, level warnings and frost-protected washer systems.

Windscreen washer reservoirs vary considerably depending on the vehicle series, year of manufacture, cab design, installation position and electrical equipment. They are fitted to MAN F90, F2000, TGL, TGM, TGA, TGS, TGX, TG3 and TGE, as well as Mercedes LN, SK, Atego, Axor, Actros, Arocs, Econic, Sprinter, Vito and V-Class. MAN Lion’s City, Lion’s Coach and Neoplan coaches such as the Cityliner or Tourliner may also have reservoirs with a specific shape, larger capacity or separate connections for windscreen and headlamp washers.

The tanks are generally made from impact-resistant, chemically resistant HDPE or PP plastic. Key differences include nominal capacity, filler neck length, mounting lugs, position of the pump connections, diameter of the sealing grommets and the presence of a level sensor. Versions with headlamp washers often have additional pump openings and hoses with a higher fluid demand. On vehicles with heated washer systems, the specific electrical plug connections and hose routing must also be taken into account.

A windscreen washer reservoir must always be identified using the vehicle chassis number. Visual comparison or selection based solely on the model name is never sufficient: within a single Actros, TGS or Sprinter series, the reservoir shape, filler pipe, pump type and sensor configuration may differ. Before ordering, also check the number of pump positions, plug configuration, outlet direction and mounting points on the cab or chassis.

Common faults include cracks around mounting points, leakage at the filler neck, porous pump grommets, detached connection nipples and a faulty level sensor. Cracks are often caused by cab and chassis vibrations, a front-end collision or frozen fluid in a system with insufficient winter protection. A visibly full tank with a low-level warning usually indicates a contaminated float, oxidised connector or break in the wiring harness. If the pump can be heard operating but no fluid reaches the washer nozzles, first inspect the tank outlet, suction strainer, hose connections and any non-return valves.

Start the diagnosis with a visual inspection for moisture traces along the seam, underside and pump openings. Then fill the reservoir with water and check for leaks both at rest and with the pump activated. Measure the supply voltage and earth connection at the pump plug while operating the windscreen washer function; compare the measured value with the vehicle specification for the fitted 12- or 24-volt system. Next, check the pump resistance and, if necessary, perform a separate functional test. A voltage drop under load is more likely to indicate corrosion in plugs, earth connections or control switches than a faulty reservoir.

Replace a reservoir if it has cracks, deformed pump seats, insufficient sealing or damaged mounting points. Repairs using adhesive or plastic welding are often temporary when exposed to washer fluid and vibration; a dimensionally accurate seal is particularly important around the pump openings. Fit new sealing grommets if they are hard, cracked or swollen. Reusing old sealing grommets can cause air ingress, resulting in pump cavitation and irregular washer nozzle operation.

Before installation, clean the suction hoses and washer lines, fit the reservoir without stress in its original mounts and check that the filler neck does not rub against cab panels. After installation, fill with washer fluid offering frost protection suitable for the expected ambient temperature. A correct fit and technical inspection before installation minimise downtime and prevent recurring leaks in the windscreen wiper system.