cobalt 2007 LT loud, rhythmic noise

I lent my 2007 Cobalt LT ( less than 24,000 miles) to someone else for a couple of weeks and ended up with a loud whirring or whining sound I never heard before. In every other way the car steers and performs as well as before but I am concerned. I probably will have to take it to the dealer but I am curious enough to try to find out what the problem might be before I do so.

It’s a rather melodic sound – something like an old motorboat or the rhythmic tire noise you get on a rough but regular pavement. You might say it even sounds sort of like a tuned muffler but the sound is not there when I stop and rev up the motor. The car sounds normal up to about 20 mph then the loud, rhythmic noise kicks in but disappears again when I drop below 20 mph. From the driver’s seat it’s hard to tell where it is coming from. I ran my hands back and forth over all four tire treads thinking it might possibly be very loud tire noise but didn’t feel anything abnormal. I didn’t see any tire bulges or other abnormalities either.

Has anyone else with a Cobalt had this problem? If not, does anyone have an idea as to what the problem is?

Thanks.

Drive the vehicle until the noise is loudest......then when you can safely do this on a straight stretch of road, turn the wheel SLIGHTLY to the left and then SLIGHTLY to the right.....if the noise is present or greater when you turn in one direction, and is less or eliminated when you turn in the opposite direction, you have a front wheel bearing problem......it's the whole hub assembly that has to be replaced....

Yep, TechII's on it, you've got a noisy hub bearing.

Thanks for the quick response Tech II. I took the car out to the freeway and found a place to try what you suggested. I went up to 65 or so then turned slightly to the right then slightly to the left. I did this 3 times. However, there was no change whatsoever in the sound or the handling of the car. I bouhgt the car new a little over 4 years ago and have 24500 miles on it. It has the original Continental tires which were rotated once at 19000 miles. The back tire on the passenger side has a slow leak and has to be pumped up from tiem to time. I would not expect to have tire problems at 24500 miles but do you think that could be the cause?

You don't feel any choppy/cupped/rough edges on inside edge of any of the tires?
Only rotated once in 24,000 miles? I would expect to see some tire issues with the lack of rotation. They should be done at LEAST every 6000 miles. That being said, you can usually hear a tire noise at low speeds also, a freshly repaved road is ideal to hear a tire noise. If your area is anything like mine, good luck finding a freshly repaved road.

I ran my hands over the inside of the tires this time but did not find any choppy/cupped/rough edges. I almost hoped I would. I did find a relatively freshly paved road but there was too much traffic to go very slow. I believe I do have some tire noise at low speeds but nothing like after getting up to 20 mph. I guess I wasn't aware that one should rotate every 6000 miles. I will certainly do so in the future. Would it be a practical idea for me to replace the tires one by one with the spare just to see if there is a change in the sounf? Thanks for your input. It is much apprecdiated.

If you have the time to swap tires, go for it, but if your not feeling anything on the tires, they are probably ok. I have seen several Cobalts with wheel bearing issues.

If it was a bearing, you wouldn't need to get up to 65 mph....normally, that noise would be there at 30-40 mph.....

The noise might not be completely eliminated, just dimished, when turning one way as opposed to another.....

It could be a tire, but you said you felt them and there was no cupping......but since you said the first rotation was at 19K, they are suspect...could even be a belt shift....

Are you sure you can't tell whether the noise is coming from the front or the rear? Have someone ride in the back to help listen...if you rotate the tires and the noise now goes with the rotation, you know it's tires...

I would do this......jack the rear end up enough so the tires are about 2-3 inches off the ground....with e-brake off, spin the rear tires one at a time, and look at the flat edge of the tire from the rear, to see if there is a huge jump(belt) or if the edges have cupping(easy to see when spun)......

Hard to spin the front tires as fast as the rears....so rotate tem, front to rear.....now with the front tires on the rear, again jack up the car and spin each wheel....like I said, look for a belt shift/break, or cupping....

As Gmtech1 said, tires should be rotated every 6K, for even wear.....I would be suspicious of the tires that are rotated to the rear and spun, for cupping.....cupping usually happens due to poor struts/shocks OR lack of tire rotation(this is due to less weight in the rear and going over bumps, the rear tires may actually lose contact with the road, and tend to cup........the front of the car is so heavy, the wheels generally don't lose contact with the surface)........

Please pardon the length of time I took to reply but it took me awhile to get up the nerve to tackle the task of substituting my spare for each of the 4 tires to see if doing so made any differeence in the noise. Sad to say it did not so I guess I will have to take it in to the local Chevvie dealer. I would rather not but unless someone has an additional step for me to try I can't thin kf any alternative.

Anyway, thank you very much for your time and consideration. You were very helpful.

Albert22

Still say it's a noisy hub bearing

Still say it's a noisy hub bearing

The prize goes to gmtech1 for his absolutely accurate solution. I took it to the Chevvie dealer and was told mit was the hub bearing. They replaced both front bearings and the nosie is no longer there. What surprised me was that the cost was covered under the power train warranth - a pleasant surprise!

THANKS GMTECH1. YOU WERE RIGHT ON.

Happy to hear! Great that it was taken care of under warranty!