Hyundai Repair: timing belt replacement, timing belt replacement, drive belts

Question
Thank you for your response!  In response to your questions:

The noise seems to originate from the engine area

When accelerating I first notice it when I get over 40mph.  It is especially noticable when I slow from 50mph or higher to a stop.  It sounds like a racecar slowing down with the humming/buzzing in the engine.

In conjunction with the noise, I feel faint vibrations in the dash and floor.

The frequency of the noise seems to be in proportion with the engine speed, although I'm not certain of this.
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Followup To

Question -
I recently brought my 2001 Elantra GLS in for a 90,000 mile service, at which time I was informed that I needed new timing and drive belts.  My question is two-fold.

First, how often should you need to replace these belts?  I had it done at 60,000, and was surprised to have to do it again at 90,000.

Second, I have had the car back for about a week and it is making strange noises that sound like the belts working too hard.  They are humming/buzzing, sounding sometimes as if I'm driving a racing car.  Is this typical of new belts or is something wrong?  I notice it especially at 45-60mph.

Thanks for your help!
Lisa

Answer -
Hi, Lisa.  Your timing belt should be replaced every four years or 60k miles, whichever comes first.  Since you've got a 2001 Elantra with 90,000 miles, I'll presume it hasn't been four years since you replaced the belt at 60,000 miles.  Chances are the shop which looked at your car didn't realize the timing belt had already been replaced.

The drive belts should be replaced whenever needed.  It's not uncommon for the a/c belt on this car to start cracking after about 3 years or 30k miles or so, so if they were replaced when your timing belt was done, it may be about the right time to do them again.

My first reaction on the humming/buzzing is that you may have a worn wheel/hub bearing.  This noise will vary with vehicle speed and will tend to get louder as the car goes faster, and as the car is turned to the side opposite the bearing in question.  But this is just a remote guess at this point.  It could be something aerodynamic such as a loose splash shield which vibrates when you drive.

Can you tell me:

Where does the noise seem to be originating?

Does it occur only within a certain range of speeds (understanding it's worst between 45 and 60 mph)?

Do you feel anything in conjunction with the noise?  If so, where, what, and how?

Is the frequency of the noise proportional to vehicle speed? or engine speed?

Answer
I'd recommend taking it back to where the work was done (especially if the noise began immediately after they did the work) to have them check the noise.  If you can feel it in the floor, it could be a sign of some sort of impending failure.  It's possible the right motor mount (they would have needed to remove this to do the timing belt) or some other component is loose.  Of course, it's also possible that the noise isn't related to the work that was done.