I have a 2006 Sonata 4 cyl with 106000 miles. I love the car and I only have had 2 problems as of yet. The first is slight oil leakage from engine gaskets which is mild and will address that later. However I have a knocking noise in my front end and knocking is exactly what it sounds like whenever i go over quick fast bumps. I had a friend of mine who is a certified ASE mechanic get my car on the hoist and the whole front end seems tight nothing is obviously loose. He called over and talked to a Hyundai service mechanic at the dealer. That Hyundai mechanic said it is probably the front struts and mounts but hard to tell. THe mechanic said its more than likely that as he has seen that more common than not. I don't want to just replace things as an elimination purpose but the knocking is all the time on fast bumps on mainly my front passenger side almost in front under where your legs are (just further ahead). Been a great car and hasn't cost me anything thus far. Do not know what to do.... My buddy will repair it because i am not going to dealer and paying that ridiculous price on parts and labor....

 

Quit going over "quick fast bumps"... thats an extreme operating condition... you is impacting the suspension hard, and the oil control valving in the strut WILL NOT flow oil that fast through valve restriction, so the oil becomes solid momentarily, and the strut becomes solid to drive the impact force right into the chassis.

Drive down a straight quiet road out away from traffic... rock the steering wheel really hard and quickly left to right and get the car rocking hard while going.. gots any noises now ??

 

Yeah, what did you expect from a car with 106,000 miles that's driven over "quick fast bumps"? Things wear out over time.

It's really hard to diagnose noise problems over the internet. I'd guess the Hyundai mechanic is probable correct. Even if the noise isn't from the struts, they probably need to be changed if they are original.