Strange sound when accelerating on highway

[KC Strip]

I was driving the 1999 Suburban (5.7L with 134K) today and noticed kind of a loud sound when accelerating on the highway. It doesn't make the sound if I let off the gas; it only makes it when accelerating. Also, I don't hear it unless I'm on the highway. I'm stumped as to what it could be - any thoughts?

 

[Colt45ws]

What did it sound like?

 

[KC Strip]

Good question. It seemed to get much louder. No clicking. If I kept on accelerating but turned the wheels to the right, the sound continued. If I turned to the left, it seemed to lessen.

 

[Throckmorton]

Bad wheel bearing, probably the left front wheel.

 

[mechtech2]

Is it an exhaust noise?
The word 'sound' covers a lot of territory.

 

[KC Strip]

Good point, mechtech2. Not sure if the noise/sound is exhaust related. How would I know for sure? Also, if it were exhaust related ... wouldn't I hear it no matter how fast I were going?

 

[KC Strip]

Throckmorton -

Would a bag wheel bearing only make noise at high rates of speed? I guess what I'm asking is if a bad wheel bearing can only be heard while traveling at least 50 mph?

 

[MrCritical]

Do you still hear the sound if the a/c system is turned off?
Belt squeal?

 

[mechtech2]

Having the noise occur when applying power indicates exhaust.
A small hole or leak can make a big noise.
Loose heat shielding can rattle and buzz also, when under load or at a resonant frequency.

 

[KC Strip]

MrCritical -

I haven't checked it yet without the a/c on but I will tomorrow and get back with everyone on it.

 

[KC Strip]

mechtech2 -

My initial reaction was an exhaust leak, but I'm not sure. What's the best way to check that? My guess is that if it is an exhaust leak it's closer to the engine rather than further away (based upon where I thought I heard the noise ... seemed like it was under the engine).

 

[ThirdeYe]

I think probably an exhaust leak or loose exhaust component. Also look at the Catalytic Converter.

 

[KC Strip]

I'll check throughout the exhaust system and see what comes of it.

 

[Throckmorton]

Quote:

---

Throckmorton -

Would a bad wheel bearing only make noise at high rates of speed? I guess what I'm asking is if a bad wheel bearing can only be heard while traveling at least 50 mph?

---

That's how it has been in my experience. And it becomes more pronounced the higher the speed and the greater the load on the wheel. If it sounds like grinding and doesn't correspond to braking it is very likely a wheel bearing. Also if you have large heavy aftermarket rims it puts more strain on the bearings and they are apt to fail sooner.

 

[KC Strip]

Thanks for the insight, Throckmorton. My guess is that it is not a bad wheel bearing. I don't have aftermarket rims. Also, I didn't hear it today - it was much cooler so I didn't need the a/c.

 

[KC Strip]

MrCritical -

I did not hear the noise today. It was much cooler, so I didn't need the a/c. I'm beginning to wonder if it was a belt squeal. If that's the case, replacing the serpentine belt is pretty simple. I'm also wondering if I should replace the belt tensioner at the same time. Thoughts anyone?

 

[mechtech2]

A good quick way to check for exhaust leaks is to stuff a rag in the exhaust pipe outlet, and have have someone rev the engine while you look underneath.
You can do this for a 1/2 minute or so, and the engine will still run, BTW.

 

[KC Strip]

Thanks for some practical advice, mechtech2!