Which type of engine component is most likely to experience fatigue due to heat cycles?

The exhaust manifold is the component most likely to experience fatigue due to heat cycles. This part is exposed to extreme temperatures and rapid temperature fluctuations during the engine's operation. The exhaust manifold channels the high-temperature exhaust gases from the engine's cylinders to the exhaust system, and as it heats up and cools down with each engine cycle, it undergoes significant thermal expansion and contraction.

These repeated thermal changes can induce stress in the material of the manifold, leading to the development of micro-cracks or fatigue failure over time. Additionally, the exhaust manifold is typically made from cast iron or steel, which can be particularly susceptible to thermal fatigue under such operating conditions. The fatigue can compromise the structural integrity of the manifold and lead to issues like exhaust leaks or performance problems in the engine.

The other components listed, while they do experience stress and wear, are not subjected to the same extreme thermal conditions regularly encountered by the exhaust manifold. For example, the oil pan mainly deals with the engine oil at a more stable temperature, while the radiator's role is to dissipate heat but is built to handle that heat transfer mechanism effectively. Fuel injectors also see thermal variations but are primarily affected by pressure and fuel properties rather than direct thermal cycling like the exhaust manifold.