2008 KIA Sorento 2.5L Diesel · FM57 DZR

A widely recognised vulnerability on the first-generation Sorento BL is the degradation of the protective internal coating inside the steel fuel tank. Over time, chemical reaction with diesel fuel causes the inner lining to flake, peel, and break down into metallic and plastic flakes. These debris pieces collect in the fuel tank pickup strainer and quickly clog the fuel filter. When the driver demands high fuel flow (such as accelerating up an incline or overtaking), the engine suffers fuel starvation, stutters violently, loses power, and cuts out completely, requiring fuel tank flushing or replacement.

Constructed with a heavy-duty ladder-frame chassis, the Sorento BL is exposed to heavy salt and water spray on UK winter roads. Moisture and road grit become trapped inside the hollow box-section chassis rails, particularly around the rear axle kick-up and trailing arm attachment brackets. Unchecked internal rust causes the chassis metal to laminate and rot from the inside out, leading to extensive structural perforations that cause MOT failure. Welding repair requires extensive fabrication and can easily exceed the market value of the vehicle.

The central crankshaft damper pulley bolt on the 2.5-litre CRDi diesel engine is vulnerable to tensile fatigue and shearing under torsional engine pulses. When the crankshaft bolt snaps, the auxiliary drive belt pulley becomes detached, instantly disabling the power steering pump, water pump, and alternator charging circuit. In severe cases, the loose harmonic balancer damages the crankshaft nose and keyway, occasionally requiring complete engine removal and crankshaft replacement to rectify.