Mystery Noise - Suggestions Appreciated

[Carmel Corn]

Hello, I have a 2007 Forester with an automatic transmission and only 12,000 miles. There is a low rumbling noise that I hear only when:

 

1. Begins at higher speeds, minimum 50 mph (no noise whatsover below 50 mph regardless of whether accelerating, coasting, etc.)

 

2. Only happens during throttle/acceleration - noise disappears when the vehicle is coasting or maintaining speed (50+ mph), and re-appears the moment I hit the gas.

 

3. I sometimes hear an occasional exhaust system rattle, not the rumbling noise, but perhaps related?

 

I know other threads touch upon wheel bearings, but would that be case when the noise only appears when accelerating? Might another possibility be the transmission?

 

The tires are the original Yokohama and again only have 12,000 miles of wear.

 

Would greatly appreciate any suggestions on where to start.

 

Thanks!

[Log1call]

Does the noise happen in all gears the same? Does the noise get noisier as you put more load on it, say by going up a hill and giving it more throttle, would the noise get louder? Harsher? Does it get noisier as speed increases, once the fifty threshhold is passed that is? Does the noise get louder as you corner? Does it sound louder the harder you corner? How would you describe the frequency of this noise... at engine speed? Wheel speed? Somewhere between?

 

We can probably narrow down the likely places then it will take a careful examination and perhaps a bit of experiance to spot what is causing the noise.

 

I suppose you have checked tyre pressures and wheel alignment?

[ericem]

Probably just the heatshields.

[Carmel Corn]

Thanks. The vehicle tires and alignment are fine. The noise seems to get louder as more load is applied. If I really hit the gas and the automatic transmission downshifts, the noise seems to get louder. It appears to be related to the wheel speed vs. engine speed (I say this because engine at higher revs produces no noise at lower mph wheel speeds....only once I get to 50 mph or so). I cannot say as to whether the continues as I corner because I ususally am letting off on the gas (therefore the noise disappears).

 

Would appreciate it if somebody could me to understand the potential link between heatshields and this noise?

 

Thanks again.

[edrach]

Your car is a bit "young" for this, but problems with the inner (DOJ) joint can give you those exact symptoms when it's bad. Very unusual for only 12K on the car. But if you find the inner joint rubber boot torn, that would be a definite sign that the axle has gone bad.

[nipper]

wheel bearing?

 

 

nipper

[Carmel Corn]

Would a failing wheel bearing only make a noise during acceleration or would it be constant regardless of engine speed?

 

Thanks again.

[ferret]

Remember, we can't see, touch nor hear this ourselves. I would check the center driveshaft, especially the universal joints on the ends. The transmission end usually wears first and exhibits a rumble/vibration when accelerating. This is difficult at best to see on the car as it's obscured by the exhaust and other drivetrain parts. But a bright light and good set of eyes can spot it.

 

I have seen this overlooked many times, and even some other mechanics and technicians looking and saying they were OK. For an 07, this is an early failure unless you have a lot of miles or live in a winter salt area. Nonetheless, it does happen.

 

If I think of anything else, I'll try to update this thread.

[unibrook]

I doubt it is a wheel bearing bcuz it would make that whurring sound very steadily regardless of accelerating/coasting etc.