What is an overhaul?

What is an overhaul?

Many friends often hear people talking about "Engine Overhaul", so what is considered an "Overhaul"?

In fact, "Engine Overhaul" has a specific definition, and it is not just a casual repair of the engine that can be called an "Overhaul".

An engine overhaul can be compared to a very serious illness, requiring hospitalization for very professional treatment, and also spending a lot of money.

An engine overhaul is to disassemble and the engine, clean and inspect all parts, and replace or repair necessary parts as needed to restore the engine performance. The main parts include: crankshaft, piston, connecting rod, cylinder liner, valve assembly, etc. In short, if the engine has a very serious mechanical failure, it must be disassembled.

The main criterion for judging whether the engine needs an overhaul is the degree of wear of the cylinder.

Due to the influence of various factors, the wear of the matching pairs of each assembly will lead to a sharp decrease in the performance of the engine. When the cylinder out of roundness reaches 0.125mm per 100mm cylinder diameter, or the cylinder cone wear reaches 0.40mm per 100mm cylinder diameter, it is necessary to consider overhauling the engine.

Simply put: the cylinder is originally well sealed, and after a long time of use, gaps are worn out.

For ourselves, there is definitely no way to know the degree of wear of the cylinder, but through some fault phenomena, we can simply judge whether an overhaul is needed. For example: the engine burns oil, emits blue smoke, has serious knocking sounds, engine abnormal noises, etc. In addition, the engine also needs an overhaul if it is flooded or soaked in water. The performance of a qualified overhauled engine is about 90% of the original standard.

Although an overhaul can make the engine look brand new, the performance cannot reach a brand new state. The technology, component precision, and assembly process of the maintenance industry cannot be compared with the original factory process, which is not realistic.

Simply put, an overhauled engine is a bit like a person with a prosthetic limb. It can still move, but its flexibility is definitely not as good as a real hand.