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'07 Sonata Making a Loud Screeching Noise - Can't Be Identified

My car - a 2007 4 cylinder Hyundai Sonata - is making loud screeching sound more than occasionally but not all the time at high rates of speed (70 - 75 mph) and ESPECIALLY when I am exiting the highway to go to the train station and I turn to the left on the exit ramp. Never the right - only the left, and it stops immediately when I touch the brakes.

About 6 weeks ago, I had 4 new tires put on, and thought maybe they were not installed properly. I saw a mechanic today who put it up on the lift and said everything looks in good order and he could not find anything wrong with the driver’s side front wheel, which is where it sounds like the noise is coming from. Of course, when we drove around in it, there was no noise. In fact, after I dropped him off and went to the train station it DID make the noise, so I turned around, picked him up and drove back exactly the same way - no noise.

It is a very, very loud uninterrupted screeching sound.

Any ideas? Thanks in advance for any insights!!

My first suspect would be a bad wheel bearing. Did your mechanic check the front wheel bearings? If not, it may be time for a new mechanic. My money would be on a bad right front wheel bearing, but both should be checked.

If the bearing(s) check out okay, the only other thing that I can think of would be possibly a bad CV joint on the right front axle, but I think that is much less likely than wheel bearings.

Also, the condition of your brake pads should be checked, since the noise apparently disappears when you apply the brakes.

Additionally, if the noise only began after installation of the new tires, it is possible that the tire installer bent a brake dust shield during installation, and that this part is rubbing and making noise.

What–exactly–has your mechanic checked so far?

He said he “put it up on the lift and checked it out” - but I know he didn’t check the brake pads b/c he said he didn’t look at them, that it could be the brake pads, and suggested I have them checked out when I come in for an oil change ( I am due in a little more than a month). The good news is I wasn’t charged today - but I am not sure he did much more than eye ball the car when it was up on the lift. I am almost certain he didn’t remove anything.

I did tell him the sound stops when I hit the brake pedal - can that be an indication that it is the brakes? (I apologize for my ignorance - I am new to driving…)

Also, the car has just over 40,000 miles on it and is 4 1/2 years old. I am its first and only owner, and I have done all required routine maintenance and upkeep. Could a car with so few miles on it have a bad wheel bearing or CV joint?

Or, with that in mind, is it more likely that it is the brake pads or the brake dust shield? (again, sorry if this is a dumb question - I am new to this car thing. I lived in cities most of my life and did public transit.)

Thank you for your help!!!

When you exit at that speed, you place a lot of stress on the brake rotors and bearings. They deflect and then the brake pad squealers rub creating the noise that is intended to let you know your pads are worn enough to need replacing. A slow test drive or the car on the lift and rotating the wheels won’t produce the noise. However, a competent mechanic should be able to check bearing play as well as brake component wear (pads worn, caliper sticking etc) to find out what is causing it.

Thank you both, @TwinTurbo and @VDCdriver!