BMW Engine Rebuild

The N57 suffers almost identical timing failures to the N47 as there is only a minor difference in design. Both the chains and guides are susceptible to failure both because of the materials used and design choices. The chains on these engines are relatively small and thin, the reduction in size and weight of the chains makes for a more efficient engine, however the trade off is strength and longevity. Therefore it makes this the most common cause of engine failure. This generally causes damage to rocker arms, valves, guides in addition to camshafts and carrier in the first few seconds. Guides can break up through wear and oil contamination. Although these failures are shared across platforms the N57 seems to suffer from this less often.

Often a secondary failure following a type of timing failure, poor maintenance or a blocked DPF. This is caused by either oil starvation or excessive back pressure. In timing: as the plastic timing guides wear they leave behind a build up of material which ultimately makes its way to the oil pickup therefore blocking it and starving not just the engine of oil but also the turbocharger. A blocked DPF will generate a high amount of back pressure, putting stress on the turbo internally and eventually leading to a large amount of through play in the shaft through wear (allowing the passthrough of oil).

A clogged DPF will create excessive back pressure and more stress on the turbocharger. Exhaust gas back pressure will also create a high stress environment inside the engine and will start to generate carbon build up internally. As well as this the turbocharger shaft will wear, have noticeable play through the shaft and allow the passthrough of oil to the intake. This also has a knock on effect on the fuel injector operation and wear.

Fuel injectors are known to fail for a variety of reasons however most commonly we see the result of emission control systems. The injectors are called upon to create an environment whereby the DPF can regenerate, this means providing more fuel. Overtime and depending on the type of driving you do, this can cause an excess of fuel to make its way down to the sump thus making the oil thinner and resulting in poor lubrication. After some time the injectors can also fail, hugely over fuel, causing massive damage inside the cylinder. This is due to the injector spraying too much fuel inside the combustion chamber during its cycle before igniting it. The large amount of fuel creates a very high temperature environment subsequently melting and breaking up the pistons. A failed or failing injector can also cause a connecting rod to bend.

Commonly caused by a lack of sufficient lubrication in a number of ways. We often find spun big end and main bearings. Likely factors for this failure include the oil pump and oil contamination/degradation. This could be down to lack of servicing, fuel injector failure, a blocked DPF and any other contaminant that finds itself in the oil. If the vehicle is driven with a knocking engine this can cause massive damage including a snapped crankshaft. Much the same as the N47. With all BMW engine rebuilds the crankshaft is often replaced with a new unit.

Poor servicing is a major contributing factor leading to engine failure. If the oil is not changed regularly a build up of particles and debris will build up inside the engine. Oil quickly loses the ability to hold carbon in suspension, so this and the change in oil viscosity commonly blocks oil galleries and the oil pickup therefore leading to failures. Because of this we are seeing the oil pumps failing, spun big end and main bearings in addition to turbochargers due to a blocked pickup.

Apart from the above these engines are known to fail in a number of preventable ways. Other failures include the intake manifold swirl flaps, which can break up and are sucked into the combustion chamber causing piston and cylinder head damage. The oil filter housing and cap, the housing has an oil return valve which can stick or break causing low oil pressure and the cap houses a valve which can fail causing the oil to pass through unfiltered. The N57 shares these issues with the N47.