My son is the same--his favourite activity is disassembling mechanical equipment!

Mecano and Lego Technic are some toys I have my eye on for my son (now 2.10) as his dexterity matures.

I have this miniature combustion engine kit in mind for my son for Christmas as a project we work on jointly; your son might be able to construct the engine more or less independently.

http://www.fatbraintoys.com/toy_companies/perisphere_and_trylon/haynes_combustion_engine.cfm

As for machines to take apart and rebuild together: electric kettles, toasters, clocks, computers, inexpensive electric toothbrushes (you can buy new ones for $5-10), hair dryers, computer printers, handheld electric kitchen mixers, fans, and vacuum cleaners are good ideas. My son enjoys plumbing, so we've taken apart the pipes to our toilets, dishwasher, sinks, and showers to show him how they function.

These are interesting sites for engineering/construction projects:

http://m.instructables.com/id/Project-Based-Engineering-for-Kids

http://www-tc.pbskids.org/designsquad/pdf/parentseducators/DS_Act_Guide_complete.pdf


What is to give light must endure burning.