Mercedes W212 Water Pump Replacement. • In this video, we work on a Mercedes-Benz E-Class W212 E220 CDI BlueTEC equipped with the 2.1 CDI OM651 diesel engine. The owner arrived with a common complaint - the coolant level in the expansion tank was slowly dropping, although there were no obvious major leaks visible under the vehicle. • After inspection and diagnosis, the source of the problem was quickly identified. Coolant leakage was found around the water pump housing area. On OM651 engines, this is a fairly common issue, especially as mileage increases and the engine experiences constant thermal cycling over time. • On this engine, the water pump is supplied as a complete assembly together with the mounting housing. The manufacturer recommends replacing the entire unit rather than replacing only the pump itself. The original factory design uses a plastic housing, which can weaken or deform over time. • In this repair, we install a much more durable upgraded solution - a fully aluminum replacement assembly. The new unit includes both the water pump and the aluminum mounting housing, significantly improving long-term reliability and reducing the chance of future coolant leaks. • Access to the pump is not extremely difficult, but for better visibility and easier filming, additional surrounding components are removed during the repair process. This includes several vacuum control components mounted above the work area. • At the same time, we perform a complete accessory drive service. A new serpentine belt, tensioner pulley, and idler pulley are installed, since it makes sense to service all wear-related components while everything is already disassembled. • One interesting technical detail on this engine is the accessory drive design. Unlike many engines, this version does not use a traditional overrunning alternator pulley. • Instead, the freewheel mechanism is integrated directly inside the crankshaft pulley. So if you ever notice that the crank pulley rotates freely in one direction but locks in the other, this is completely normal and part of the original design - not a defect. • #supermechanik #artempankovich #carservice #goldenhandsmechanic #CarRepair - @artem_pankovich