Diagnosing Suspicious Noise - Ford ZX2.
My daughter’s car makes a noise that sounds to me most like a bad wheel bearing. She thinks it sounds like her brakes when the rotors have rusted after she has not used it for a few days. It is droning, whooshing, scraping noise. She says it started a few hundred miles ago. It changes pitch with speed. It does not change if the car is taken out of gear and rolling. (It is a manual.) It does not do it when standing still and the engine is revved in neutral. I jacked up one front wheel at the lower control arm and slowly engaged first gear at idle. It makes the noise. I did the same with the other front wheel. Same sound. (Note that the other wheel is on the ground and not turning when doing this test. The car does not have traction control or a locking differential.) No clicking or grinding from the CV joints when making a turn. Even at full lock. I think the only thing common to both axles when in gear would be the output shaft of the transmission. Thoughts?
In a well controlled manufacturing process it is very likely they both fail at the same time. It may be that the differential carrier bearings in the transmission are failing. Less likely than wheel bearings but certainly possible.
While the car had one wheel jacked up, did you check for bearing play? Roughness? Slop in the CV joints? Checking those should narrow things down a bit. If both sides feel OK, I’d suggest driving it until it gets worse. If it is the transmission, you might start looking now for a shop that can rebuild it or a rebuilt unit. They may not be so easy to find.
For wheel bearing noise, usually the sound will increase or change pitch if you make a sharp turn. Turning left, the right wheel and bearing recieve more weight and the sound should increase, and vice versa. If the sound doesn’t change during sharp turns, I wouldn’t say it eliminates wheel bearings as the cause, but it would seem less likely that it’s the wheel bearings.
I jacked up the car and checked the bearing play last night by pulling in and out and by rocking with my hands at the 9 o’clock / 3 o’clock positions and at the 12 and 6 positions. The right wheel had no slop in any of those tests. The left had a little play at the 3 and 9 position which I traced to a worn tie rod end. I also turned the wheels by hand listening and feeling for any grinding or clicking in the bearing or the CV joints. They seem to be fine. The wheels turned easily the only sound being the dragging of the disc pads. I did the above with the wheel jacked up by the control arm so it was in a “normal” position and when hanging down with the jack stand on the frame. I also turned the wheels from lock to lock and turned them to put the CV joints in the most flexed positon.
I did not. I had my daughter drive in tight right and left circles at her school. She says no noticeable difference. I did notice last night that while the outer brake pad is nice and thick the inner one on both sides is almost down to the backing plate. So I’m thinking the wear sensors are making all the noise. But the sound does not stop when I apply the brakes which is my past experience with wear sensors. On Friday I will replace the pads and rotors. While it is apart I will retry the driving the wheels with the engine at idle before in installing the new pads and rotors. I’m thinking it is the worn pads at this point. Cross my fingers. Will let all of you know.
I unscrewed the fill plug and a little transmission fluid dripped out. It was a pinkish brown that I would expect of used transmission fluid. Did not smell burned or odd in any way.
When you do the brake pads, be sure to take the caliper slide pins out, ensure that they’re smooth (not worn on one side or corroded) and grease them. They could be hanging slightly, causing one pad to wear against the rotor.
Yes. I pull the slide pins, clean the hole in the caliper, buff the pins smooth, and grease them every time I change the pads. But that effort doesn’t seem last very long as the inner pad is always worn out while the outer pad has lots of material left. I always say I’m going to pull them a year later but it never happens. I think the pads might be identical, therefore reversible. I’ll have to check that tomorrow.
I had both front wheel bearings fail at the same time on my VW Rabbit, so don’t discount that possibility. Wheel bearing failures are usually reported as a “growl” or a “roar” that gets louder the faster you go. On my Rabbit it sounded like I was driving on pavement that had been roughed up in preparation for re-paving, definitely a roaring sound. You description of the sound seems a little different from that, so before replacing the wheel bearings make sure it isn’t the brakes. Might just want to replace the pads and rotors first, especially if they’ve been installed for some time.
I removed the brake calipers and rotors. “Drove” the car while on the jack stands. Prevented the right hand hub from turning then the left hand hub (a differential is an amazing device). It is the left wheel bearing.