Hello I will help you with your question,
Which engine do you have in your Sonata?
There are two belts on this engine with the adjuster for one below the power steering pump. Loosen the lock nut on the adjuster bolt and loosen the bolt. You may have to loosen the nut on the pump pivot to allow it to move and loosen the belt.
The other adjuster is on the top of the alternator. Again loosen the lock nut on the adjuster bolt and turn the adjuster to loosen the belt. You may have to reach through the wheel well to loosen the pivot bolt for the alternator. In any case you will have to reach through the wheel well to string the new belt around the crank pulley. Once you have the belts installed tighten the adjusters until you can just turn the belt 90 degrees at its longest span between pulleys. Remember to tighten the nuts on the adjusters and the pivot bolts
Let me know how I can help you with this
NO the 6 cylinder has a serpentine belt which has an automatic tensioner. You put a wrench to the center bolt on the tensioner pulley and rotate clockwise to move the tensioner away from the belt enough to slip the belt off a pulley and slowly release the tensioner. Unstring the old belt and restring with the new belt leaving the same pulley off that you used to remove the old belt. Put the wrench back on the tensioner pulley and turn clockwise again til you have just enough slack in the belt to slip it back on the pulley and release the tensioner. Check to be sure the belt is on all the pulleys and you are done.
Let me know what further questions you have about this
If you turn the belt flat against the timing cover it will just fit or you can loosen the two bolts that mount the tensioner to the front of the engine. They are tight so use a six point socket if you are going to loosen them