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Rebuilt engines are also referred to as overhauled engines. Engine rebuilding involves taking apart the engine and checking each part. The parts that are of no use are scrapped and new replacements are obtained and fitted. Parts that can be used are cleaned, inspected and machined before reuse. Care is taken to ensure that the overhauled engine meets the latest manufacturing specifications.

Rebuilt Engines

The Challenge

Rebuilding used engines is very challenging because the rebuilding firm must ensure that the overhauled engine works exactly like a brand new engine. The rebuilder has to offer a warranty that almost matches the warranty that comes on a new engine. Such remanufactured engines work like new and can enhance your vehicle’s life and save you loads of cash. They also make you environment-friendly.


On a technical level an overhauled engine is different from a rebuilt engine. An overhauled engine typically does not involve machining parts – the mechanic replaces the parts that are old or worn out and that’s it. On the other hand, remanufacturing an engine involves machining certain parts that have effective reuse value, and replacing only those parts that are not working. After the machine is rebuilt, it is tested against a new machine to figure out if it performs like new. No such tests are carried out on overhauled engines. That said, in today’s times, the words “overhauled” and “rebuilt” are used interchangeably. Therefore if your rebuilder talks about overhauling an engine, he is likely talking about rebuilding it. Take precautions though and check with him if he means the same thing.

Machined parts include the piston-cylinder system and machining involves re-boring the cylinder channels and fitting the pistons into the new, larger cylinders. Bearings are cleaned, smoothed and greased. The camshaft is re-grounded and its heads are resurfaced. The rods are gauged with precision after machining. Small time parts such as gaskets, belts, etc., are replaced.


You would have understood by now that a r/ebuilt engine contains parts with different operating histories. This is the reason why such engines are not guaranteed for as long as a new engine. That said, every single part that goes into a remanufactured engine is thoroughly inspected and tested. In fact the entire rebuilt engine is tested right beside a new engine and the rebuilder ensures that his engine performs just like new. Every single part that goes into a remanufactured engine conforms to the current OEM standards and specifications.

This was all the “grease” you always wanted on remanufactured engines.

Clive K. Malley is a blogger and car fanatic who rebuilds vehicles using remanufactured engines.