Whining/Almost vibrating sound at 40+ MPH

FINNADDICT9898

MEMBER
2006 VOLVO S40
2.3L
5 CYL
2WD
AUTOMATIC
150,000 MILES

OK folks here is the dilemma:

06 S40 w 150k miles. I noticed a few weeks ago there was a whining/vibration sound coming from under the car as I pass 40 MPH. Took it to the shop, they didnt notice anything---even when I rode with them and said "dont you hear that?" The answer was "ummm no". The offered to change out "the bearings" but were VERY insistent that this MIGHT NOT solve your problem. The tire pressures are good, the alignment is good. The only issue Ive had w the car in 8 years is the AC compressor, and that was fixed 2 yrs ago and hasnt been a problem since.

Any idea on what this may be. Its more of a "sound" than a vibration. Almost like something is spinning out of balance---but just SLIGHLY out of balance. The steering wheel does not shake or shimmy. It stops on a dime and does NOT pull left or right on a hard brake. The brake rotors are fairly new as well. IM out of thinks I know to check for and Im not going to roll the dice on bearings only to find THAT wasnt the issue.

HELP!

JM

1 Reply

CARADIODOC

MECHANIC
33,873 POSTS

There is a tool you might be able to borrow or rent from an auto parts store that borrows them called the "Chassis Ear". It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Be aware that many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises.

To identify a noisy front wheel bearing, a mechanic will run the car in gear, on a hoist, then listen next to each one with a stethoscope. The noisy one will be pretty obvious. You can also jack the front end off the ground, reach over the top of a tire, wrap your fingertips around the coil spring, then feel for the vibration in the spring as you rotate the wheel by hand.