What are the reasons for the loud engine noise in the Corolla Hybrid?

[OliviaLynn]

The reasons for the loud engine noise in the Corolla Hybrid are as follows: Carbon buildup: As old engine oil becomes thinner with use, carbon buildup increases. Thinner oil can lead to oil leakage, resulting in more carbon buildup and a significant loss of power. When new oil is added, the engine may not adapt to the oil's viscosity immediately, potentially causing higher RPMs and increased engine noise. Poor sound insulation: If the engine sounds normal from the outside but the noise seems loud inside the car, it indicates poor sound insulation. Check the vehicle's sealing strips for signs of aging. Alternatively, improving the vehicle's sealing effect may help reduce the noise. Low coolant level: When the coolant temperature is too low, issues can arise, and the engine noise may increase. It is advisable to check and replace the coolant to prevent further problems.