What Causes the Loud Cold Start Sound in BMW 640gt?

[BenjaminLynn]

Introduction to the reasons for loud cold start sound in BMW 640gt: Engine Carbon Deposits: The reason is that as old engine oil becomes thinner with use, carbon deposits accumulate more and more. Thinner oil is prone to leakage, leading to increasing carbon deposits and significant power loss. When new oil is replaced, the engine may not adapt to the oil's viscosity immediately, potentially causing higher RPMs and resulting in increased engine noise. Incorrect Engine Oil Specifications: Or excessive oil quantity. When there is too much oil in the engine, it creates unnecessary resistance to the crankshaft rotation, affecting power output and increasing fuel consumption. Carbon deposits in the combustion chamber, when red-hot, can also cause pre-ignition. Moreover, carbon deposits accelerate wear on cylinders and pistons and negatively affect oil quality. In summary, excessive oil increases the stirring resistance of the crankshaft and connecting rods, leading to louder noise.