Mechanics

I HEAR A LOUND HUMMING NOISE WHEN DRIVING AT SPEEDS FROM 35-60 MPH WHAT COULD IT BE?

1999 Mercury Mountaineer • 128,000 miles

I have a 99 mercury mountaineer 5.0 v8 and its making a loud humming noise when driving at speeds of 35-60 mph. Noise starts of low then gets louder at 40-55 mph unless I let go of gas pedal then it just goes away until I start to apply it again but doesnt get louder if I apply the passing gear just stays the same until like I said I let go of the pedal which I think is wierd but cannot figure out what that noise is. What do u think it could be?
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Danny8109
May 24, 2012.



Noisy front wheel bearing. Any tire and alignment shop, and most mechanics can identify which one is responsible.

Caradiodoc
May 24, 2012.
All the wheel bearings are good the noise comes from under u vehicle and noise stops when gas pedal is not applied while rolling

Tiny
Danny8109
May 24, 2012.
How do you know the bearings are good? The only way I have ever had good luck finding the noisy one is with a stethoscope and running it in gear on a hoist.

If you're thinking this noise is being caused by something rubbing on the engine, you should be able to make it occur by doing a light "brake stand". Put it in drive, hold the brake, and press lightly on the gas pedal. That will cause the engine to rock a little. If you hear the noise, have someone do that while you look under the hood. You can also look on the inside of any plastic shields to see if there's signs of a pulley rubbing. That is typically caused by a collapsed engine mount that lets the engine sit a little lower than normal on one side.

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.

Caradiodoc
May 24, 2012.
Ok thanx ill see if I can try that if not do u have anymore suggestions that I can try incase I am not able to do this

Tiny
Danny8109
May 24, 2012.
One of our other experts says he can find the noisy bearing by rotating a front wheel with one hand while feeling for the vibration on the spring or strut, (on small cars) with the other hand. I never tried that myself yet.

Older Chryslers, Fords, Toyotas, and Hondas used pressed-in bearings. With those it was easy to determine which one was noisy by turning left and right as in changing lanes at 35mph. If the noise got worse when turning left, the right bearing was the culprit. They get noisier when more vehicle weight shifts onto them, and get real quiet when you turn the other way.

With the newer bolt-on assemblies, it is impossible to know for sure which one is noisy just from driving the vehicle. I used to be fooled many times until I started using the stethoscope. You might turn left, it gets louder meaning it should be the right one that's noisy, and it turns out to be the left one. It can sound like the noise is coming from the right side, and the left bearing is noisy. There's just no sure-fire way to tell by driving, but the good news is if you replace the wrong one, the old one can be installed on the other side. With the older pressed-in bearings, they had to be destroyed to remove them, but fortunately there was never a need to remove them other than to replace them.

Once I started using the stethoscope, I replaced the correct bearing 100 percent of the time. When you listen underneath next to each bearing, one will sound a little rough, but then the other one will be very noticeably louder. If you don't have a stethoscope, auto parts stores sell them for under ten bucks. If you have a Harbor Freight Tools store nearby, they will probably have them too.

Caradiodoc
May 24, 2012.