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Jim Grant's Tech Tips
'97 Mercury Sable Wagon, Vibration & Noise
Q:
My
'97 Mercury Sable Wagon with a 3.0 24valve engine and 105K miles is exhibiting
a constant, pronounced vibration and muffled rubbing noise coming from
the left front. It seems to be in time with the speed of the car, not
the engine, and is the same when the car is rolling in neutral. It doesn't
change when making turns. I suspect the axle bearing, but after jacking
up the car I can't detect any looseness or end play in the hub when I
rock the wheel or if I try prying between the lug plate and the steering
knuckle with the wheel and brake rotor off. After removing the brake caliper,
I can't detect any unusual vibration or noise when I spin the wheel by
hand. The bearing seals do not appear to be leaking. Also, after driving
several miles at 40-50 mph, the end of the axle shaft is only warm to
the touch, and no hotter than the other side. Before I replace the axle
bearing, is there anything else that could be causing this? Perhaps the
bearing at the other end of the half-shaft, inside the transaxle case
is the cause? How can I tell the difference? Are there any other suspects?
-
Joe N.
A:
You’ve
really done a good job of covering the bases. I’m inclined to agree
with you that the wheel bearing is the culprit, but as you have found
it is not always easy to prove. Allowing the vehicle roll while in neutral
removes a good amount of load from the transmission/transaxle. Generally,
if the source noise is from that area it will be reduced. Because the
noise doesn’t change, the wheel bearing, which always has the load
of the vehicle weight is once again suspect. A wheel bearing doesn’t
have to be loose, have signs of seal leakage or even feel rough as the
wheel is spun to be a noise source. In some cases the only way to tell
is to remove the bearing and spin it in your hand to get a feel for the
problem. One other note; try rotating the tires. We’ve had tires
make a noise that you would bet coffee is a bad wheel bearing. It’s
just all part of the fun you can have with cars.
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