What does rebuilding an engine mean?

Updated July 19, 2017

"You need an engine rebuild" can be some of the scariest words a car owner can hear from his mechanic. These are also words that can be accompanied by images of hefty bills and months of the car sitting unused in a shop. While that can, in fact, be a reality, the phrase "engine rebuild" can encompass a broad range of definitions.

Why an Engine Needs to Be Rebuilt

A engine may need to be rebuilt for a number of reasons, but they all involve the internals of the engine, which include components such as the connecting rods, the crankshaft, pistons and assorted bearings and seals. A motor's pistons ride up and down inside the engine's cylinders. There are rings installed around the pistons which seal them, which create the motor's compression. If the rings become worn, the engine rings will need to be replaced, which entails a teardown of the engine. An engine can also need a rebuild because of a lack of oil, dirty oil destroying bearings over time or by the engine being over-revved, which can break a connecting rod and cause other problems.

What Is Involved?

The first aspect of an engine rebuild is removing the motor from the car, followed by an entire disassembly of the motor. After that, an engine rebuild can be as simple as disassembling the engine, cleaning the parts, machining the crankshaft, cleaning up the bores then rebuilding the motor with the same pistons and rods but using new bearings and rings. It can also refer to the replacement of the pistons as well as the use of new parts everywhere else in the engine.

How Much Does it Cost?

Rebuilding an engine is generally fairly expensive and usually costs at least a couple thousand dollars or more. The engines in some high end cars, such as BMWs, Porsches and Ferraris, can end up costing between £6,500 and £13,000 or more depending on the car. Costs for building an engine include machine shop costs, the new parts, removal and installation of the engine as well as the dozens of hours it will take to perform the work itself.

How Long Does it Take?

It usually takes at least several full days of work to remove an engine, rebuild then reinstall it. It can also take far longer, depending on the complexity of the engine and the car that the engine came out of.

Can I Do it Myself?

While it is possible for the amateur mechanic to rebuild the engine in his car, this is not a job that should be undertaken lightly. There are many specialised tools that are needed, from the engine hoist to remove the engine to tools for assembling the internals of the motor. Engines are built to extremely tight tolerances. If there are any major discrepancies when the motor is built, they can cause the engine to run roughly, or not at all, which can lead to a much shorter lifespan. Generally, an engine rebuild is something that should be left to an experienced mechanic.

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About the Author

William Zane has been a freelance writer and photographer for over six years and specializes primarily in automotive-related subject matter among many other topics. He has attended the Academy of Art College in San Francisco, where he studied automotive design, and the University of New Mexico, where he studied journalism.