Does the 2006 BMW X3 have a timing belt or chain?

The 2006 BMW X3 has a timing chain. This is typical a "no-maintenance" part, beyond the typical engine lubrication. However, timing chains can and do fail, often in spectacularly messy and noisy ways. If You hear a rattling, clacking, or Your engine hood pops up, and a metal chain flies out, You very well might have an issue with the timing chain in Your X3. Typically, though, the part that's going to fail is the tensioner, which will allow the timing chain to become too loose, which then results in it coming off the guides. This is bad, so when You do Your maintenance, or have it checked over at the dealer, always check that the tension is still correct.