Water pump is broken.
Heater core is clogged.
Thermostat is broken.
Oil pump is damaged.
Oil level is low.
Engine oil is old, too thick, and loses lubricity.
When any of these occur, different parts of the engine will become damaged. If the engine overheats, it's common for head gaskets to fail which introduces coolant inside the engine block within oil galleys. This dilutes the engine oil and causes a lack of lubrication, or excessive heat.
Rebuilding an engine involves removing the engine from the vehicle and completely disassembling it. Once the engine has been disassembled, cleaned and inspected, all the damaged parts will be replaced with new or refurbished replacement parts. All the new gaskets, seals and lubricants are used in the assembly of the rebuilt engine.
1. The length of the lifespan of the engine will be extended because of the closeness of the inspection done during the engine rebuild as well as all of the new parts.
2. You are recycling engine parts to help reduce the amount of scrap in the environment by not replacing the entire engine but rather replacing the specific parts of the engine that were damaged and keeping the ones that were still in working condition.
3. The best benefit of engine rebuilding is the connectivity and compatibility with the existing ECU and electrical system. The ECU is programmed to communicate with the engine originally installed in the vehicle. With new engine installs, often the ECU has problems connecting and communicating with the new engine, and with engine swaps the ECU will either have to be reprogrammed or replaced entirely.