I recently bought a 2005 Buick Century with 86,140 miles. It has a few things my old Century didn’t have including traction control, anti-lock brakes and 4-speed automatic overdrive. When I slow down to negotiate a sharp turn at an intersection, I sometimes hear a brief humming sound from the front end. It lasts for a second or two. It happens after the car’s been driven for about an hour. I don’t know if it’s the transmission, the brakes or power steering. It doesn’t matter if I turn right or left. Any ideas about the cause of this symptom will be appreciated.
Is your foot on the brake when you turn and is the humming while the wheel is turned and if so, does it stop when you start to return the wheel to center?
yes
Have you checked the fluid level and color in the power steering reservoir?
Are there any unusual wear patterns on the tires, signs of one being out of round, either front or back? Does the car seem to handle bumps in the road ok, no unusual amount of jostling to the passengers when going over a bump?
Here’s an update. About seven hours after my initial post, the car made the same sound WITHOUT turning the wheel sharply. It made the sound before I came to a stop at an intersection. I previously checked the color of the PS fluid and added a little with no results. According to Carfax, the PS pump was replaced at 48,500 miles. There are no signs of unusual tire wear, the handling and the ride are fine. Could it be a transmission problem? My transmission fluid was low, I added a little with the correct type and I think I’ll add a little more being careful not to overfill it.
If it occurs only with the brakes on, that points to the ABS system…sensors (common) or (gulp) actuator.
Topping off the fluid doesn’t always result in an immediate change if the fluid is indeed low. You also need to make sure you’re using the correct fluid. Any old fluid won’t do.
I am not certain, but the century is a pretty old model. Modern steering systems are mostly self bleeding. Older systems required that they be bled manually. If it was low, and the system took in air, merely topping off the fluid wouldn’t do anything for trapped air. So the pump makes a grinding/humming noise.
Even if it is self bleeding, it’ll take some time to work itself out.
A couple of months ago, I had to change the power steering cooler in my car and it took a little bit of driving for the noise to fully go away after flushing and cycling the fluid through. It would make the noise while steering at any angle when it was low prior to fixing the leak even between top-offs.
It’ll always hum a little when you steer it fully in one direction or another.
If the anti-lock brake system is kicking on during stopping maneuvers, that could produce a sort of humming noise. Likewise for the traction control function.
What can happen, the computer is reading the rotational speed of all four wheels all the time. They should all be rotating at about the same rpm right? But if one looses traction, then its rpm won’t match the other three. So the computer then automatically activates the anti-lock brake system to get them to all match up again, the idea is to stop that one wheel from skidding.
But if the computer is mistaken, and it thinks one of the wheels is skidding, but it actually isn’t, then this symptom could result, as mentioned above by @insightful .
Here’s another update. Two days ago my front end made that same humming sound AFTER taking my foot off the brake pedal and gently accelerated from a crawl. Could it still be a problem with the ABS?
^^ If the sound started with no brakes on, it does argue against ABS.
But, do you have traction control?
insightful: QUOTE OP “I recently bought a 2005 Buick Century with 86,140 miles. It has a few things my old Century didn’t have including traction control, anti-lock brakes and 4-speed automatic overdrive.”
I had traction control inappropriately engage ABS one time. I now remember to turn it off when approaching that curve and another which is very similar.
Good catch, Sarge. So, OP, can you turn off the traction control and see if the noise goes away?
Yes, I have traction control.
I don’t know how to turn off the traction control. I’ll have to consult my owner’s manual and possibly my service manual. Also, I did notice this morning my “check engine” AND “trac off” warning lights came on after I backed out of my driveway. The lights went off when I stopped and re-started the car.
Sometimes the engine computer will turn off the traction control when it thinks theres a problem somewhere else. Don’t presume the check engine light on and the traction control off lights means there’s a problem with the traction control. If the CEL comes on, there may be a stored diagnostic code in the computer memory. That’d be the place to start.