Oil pan

The oil sump forms the lower sealing section of the engine lubrication system and serves as a reservoir for engine oil. On MAN and Mercedes trucks, buses and vans, an oil sump must not only hold sufficient oil volume, but also withstand vibrations, thermal cycles, stone impact and contact risks underneath the vehicle. The correct version is always determined based on the chassis number. Visual comparison or selection based solely on the model name is never sufficient, as the engine variant, chassis configuration, oil capacity, oil pump pickup, sensor connections and sump depth may differ.

Oil sumps differ by engine family and vehicle application. For example, a MAN D08 or D26 has different mounting patterns, oil capacities and pickup pipe configurations from a D20, D38 or older D28. Mercedes uses a variety of versions on, among others, OM 904, OM 906, OM 457, OM 460, OM 471 and OM 473 engines. Even within a single engine family, the oil pan, sump gasket, oil level sensor, drain plug and mounting of a protective plate may differ depending on the Euro emission class, cab configuration and vehicle chassis.

Traditionally, oil sumps are manufactured from pressed steel, aluminium alloys or cast aluminium. Steel versions are impact-resistant and relatively easy to repair in the event of minor deformation. Aluminium sumps offer a rigid construction and good heat dissipation, but are more susceptible to cracking after an impact. Plastic sumps are also used, generally manufactured from glass-fibre-reinforced engineering plastics or composite materials. These plastic sumps reduce weight and can dampen noise and vibrations. However, they require precise fitting: excessive bolt torque, incorrect sealing rings, aggressive cleaning agents or local heat exposure can cause deformation, cracks or leakage.

A leaking oil sump is often only noticed through oil traces on the underside of the engine block, a falling oil level, oil droplets on the undertray or a low engine oil level warning on the dashboard. The cause is not always the sump itself. First check the valve cover, vacuum pump, crankshaft seals, oil filter module, oil cooler lines and the oil level sensor connection. Oil can be spread across the sump by driving airflow, causing a leak higher up to be incorrectly diagnosed as a sump fault.

Clean the entire underside with a suitable degreasing agent and then allow the engine to reach operating temperature. Locate the first fresh oil traces using an inspection lamp, optionally supplemented with UV dye in the engine oil. Check the oil sump flange for distortion using a straightedge and feeler gauge; an uneven flange will cause leakage despite a new sump gasket. Inspect steel sumps for dents near the oil pump pickup: a pushed-in bottom can reduce clearance to the pickup strainer and cause oil pressure problems. On plastic sumps, hairline cracks around mounting bushes, the drain plug and sensor mounting must be checked carefully.

Replace an oil sump in the event of cracks, porous aluminium, severe corrosion, damaged drain plug threads or a distorted sealing flange. Always use the specified sump gasket, liquid sealant or integrated sealing edge for the engine version concerned. Remove old sealing residue without damaging the contact surface of the engine block or oil sump. Fit the mounting bolts in a crosswise sequence and tighten them to the specified torque; plastic sumps in particular are sensitive to overloading of the bolt bushes.

Always renew the drain plug sealing ring, the oil level sensor seal and any damaged mounting bolts. Then refill with the specified quantity and specification of engine oil through the oil filler tube, start the engine, check the oil pressure and inspect again for leaks. Braem NV helps identify the correct parts and provides technical support to minimise unplanned downtime for trucks, buses and vans.