What could cause a large build-up of sludge in the crankcase of an engine?

A large build-up of sludge in the crankcase of an engine is primarily caused by the degradation of engine oil over time, which can be accelerated by certain conditions. In this case, leaking cam bearings contribute to sludge formation by allowing contaminants and metal particulates to enter the oil system. As the oil becomes contaminated with these materials, it loses its ability to lubricate effectively, leading to the formation of sludge.

Additionally, the leaking cam bearings can cause localized overheating due to inadequate lubrication in critical areas, further worsening the oil’s condition. This combination of contaminants and potential overheating can greatly increase the likelihood of sludge accumulating in the crankcase.

Other factors like overheating, low oil levels, and dirty fuel injectors have their own effects on engine performance and oil condition, but they do not directly contribute to sludge formation in a manner as significant as leaking cam bearings do. Overheating can lead to oil breakdown, while low oil levels can lead to insufficient lubrication but do not directly cause sludge buildup. Dirty fuel injectors primarily affect fuel delivery and combustion efficiency rather than oil quality directly.