Hyundai Repair: 2006 Sonata noisy start, chain tensioners, ugly noise

Question
my 2006 Sonata with 30K miles has started to make a ugly noise when starting for the first 5 seconds.  I have tried to turn off the AC but it does not change.  it does not happen when I turn the car off then on again, car must be sitting for 15-30 minutes  

Answer
If you have the V6, the ratchet mechanism on one or both of your timing chain tensioners has failed.  This is a well-known issue, and Hyundai has released a redesigned part to correct it.

Your timing chain tensioners are primarily operated by oil pressure.  To keep them extended when the engine is not running, there is a rod with a ratchet on it that keeps the tensioner piston from returning too far.  If that ratchet mechanism fails, the piston will release the tension from the timing chain until oil pressure is built up again.  The rattling noise you hear is caused by the loose chain slapping around.