Under what circumstances does an engine require a major overhaul?
2 Answers
An engine requires a major overhaul under the following circumstances: 1. When there is excessive clearance between the piston and cylinder wall causing blue smoke emission, a major overhaul is necessary. 2. Severe black smoke emission from the engine. If cylinder pressure measured with a compression gauge is below normal values, a major overhaul is required. 3. Abnormal noises during engine operation. When unusual sounds are detected, the engine must be disassembled for inspection or measured using an engine noise detector. 4. Knocking sounds from connecting rod bearings (big end and small end bearings), especially when the small end bearings are severely burnt and the crankshaft shows significant wear. 5. Scuffing sounds from cylinder walls. Upon disassembly, severe scoring is found between pistons and cylinder walls.
I've been driving a taxi for over a decade, so I know exactly when an engine needs major maintenance. Generally, after hitting 80,000 kilometers, it's time for a major service – think of it as a middle-aged health check. The spark plugs should be replaced by then; the original ones have served their purpose. The oil filter and fuel filter must be completely renewed, like giving the car fresh blood. The timing belt needs thorough inspection – if it snaps on the highway, the engine is done for. The throttle body is surely caked with thick sludge and needs a deep clean. Finally, check for carbon buildup in the cylinders with a borescope to see if the piston tops are black. This full service can add years to your car's life, far better than breaking down midway.
