BMW 520D Engine Rebuild
BMW 520D N47 Failure
We recently had a BMW 520D with the 2.0 N47D20C in for an engine rebuild. This vehicle was unable to start, this is due to the timing chain breaking and wrapping itself around the fuel pump sprocket
This engine will fail in various different ways including timing failure, spun conrod bearings and spun main bearings. In this case we have a broken timing chain, guides, rocker arms, cracked camshaft carrier, bent camshafts and turbocharger failure.
After the engine is stripped we find another common issue with the oil filter cap. The small valve in the cap was completely missing which meant oil was passing through unfiltered. Luckily this is caught and didn’t have a chance to cause major damage to the bottom end.
The lack filtration means the condition of the engine oil is very poor and at the point of causing spun bearings. This is most likely the cause of failure with the turbocharger, a large amount of play in the shaft allows the passthrough of oil and could cause another failure, so this is replaced.
520d n47d20c ENGINE REBUILD
After the failure had been identified we began the process of cleaning and rebuilding this unit with new parts.
We carefully install a new crankshaft with main bearings into the block after installing the oil jets. Now 4 new pistons and conrods are installed along with a new set of bearings and piston rings. The lower timing assembly and oil pump is built up with new parts along with the front and rear seals and sump. Furthermore the oil pump is stripped and checked for damage, cleaned and reassembled. A new head gasket is installed upon attaching the cylinder head. New rocker arms, hydraulic tappets, camshafts and carrier are installed with the upper timing assembled. Finally the rocker cover is installed with a new gasket to make the bare engine assembly.
After this process the ancillaries need to be reattached to the engine so this could then be refitted to the vehicle. Once back in the car a new oil cooler gasket, oil filter and cap is installed along with new oil & coolant. Once the vehicle is completely reassembled we test the vehicle to ensure a good running operation.