Failure phenomenon: a mileage of about 190,000 km, models for the F18, N52 engine equipped 2009 BMW 520Li sedan. After cooling Car fault exclusion system, the engine noIse Is substantially greater than before. We have learned through an online engine noIse Is so great solution to our shop for testing, after the store reception, regIstration.
Failure AnalysIs: maintenance staff measuring hydraulic engine lubricating oil, when 750r / min Is 220kPa, 2500r / min to 550 kPa, within the normal range. With a stethoscope to lIsten to feel the noIse as the engine speed increases and increased, and the sound from the head unit removed the cylinder head inspection and found serious exhaust camshaft wear (Fig. 1). Check the cylinder wall, there Is no obvious wear sCar. Communicate with the user to know the Car when the cooling system fails, the problem was dIscovered in time, when going to the toilet quickly turn off the engine did not restart.
Maintenance master analysIs, since the engine oil film occurs between the hot exhaust camshaft and the bearing Is rapidly evaporated, the part surface of the rotary contact results directly mechanical wear. Since the cooling cylinder lubricating oil, and a long time Is not overheating, and thus escaped unharmed. Given the damage the engine, decided to replace the cylinder head assembly.
Solution: Replace the cylinder head, troubleshooting.