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2001 STS *SLIGHT* Howl At Speed


JasonA

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As I settle in with the new STS, and start listening to quieter music and enjoying the drive, I notice a VERY VERY slight howling noise at speed, but curiously, only in a very specific speed range. About 59-65 mph. I've never had a bad wheel bearing before, but I'd say it sounds SORT of like a bad wheel bearing, but the noise is just EVER so slight (nobody else would hear it), and it only seems to happen at those speeds. If I go a lot faster, it seems to go away. And if I slow down to 58 mph or less, it shuts off like a switch.

There is no graininess in the steering wheel or floor, and the noise doesn't change with loading one side of the car or the other (turning the wheel slightly). Very odd. I'm not all that concerned yet about it...just curious as to what it could be. The car is supposedly under the certified warranty through July, so if it is an issue, I hope it gets worse (more apparent) by then so I can take it in and have it checked out.

Any ideas? Anyone else have a slight noise like that at speed?

Thanks

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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Could just be the tires on it, wind passing threw somewhere, could even be the exhaust note at those certain RPMs. Turn the music up or go faster I guess :P

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Thanks guys. Engine speed at that road speed is right at 2000 rpm. I'll keep an ear to it to see if I hear the same noise at a slower speed in a different gear.

Yes, air filter box and pipe are tight. It even has a resonator on the intake tube. I'll double-check all that stuff.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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When my front wheel hub went bad on my 99, I couldn't hear the noise at first ... my wife mentioned it, as it was more apparent from the passenger seat ... a very slight howl, only at certain speeds.

My mechanic couldn't be sure with a road test, but a stethoscope pointed at

the wheel under speed confirmed it.

My replacement hub came with an abs sensor ... if its a wheel bearing, it will definitely become louder long before July. I think my hub was about $275 Cdn, for a cheap aftermarket version.

I'd give it a few weeks, then have the dealer investigate under warranty.

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The howl may be a half-shaft ringing, which can be caused by a wheel bearing, a CV joint, a differential looseness, or anything that couples regular vibration to the half-shaft. That's the way that a hub bearing would generate a hum. Differences:

  • A hub bearing would howl at cerain speeds, or above a certain speed.
  • A CV joint would cause the howl only on slight acceleration or deceleration, and a warble may be present.
  • A gear whine would be present only on slight deceleration, or on slight acceleration, but rarely both, and would be present at any speed at which the engine could prove very slight acceleration or deceleration.
A remote microphone that a mechanic uses to listen while you drive will tell the tale.

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I called my local dealer and they confirmed it was still under the CPO warranty, so I made an appointment next Wednesday. We'll see what they find.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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I have an 03 STS and I hear no howl at any speed. Might be the tires?

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Also consider that your serp idler wheel or tensioner wheel is making noise, just a thought..

A bad hub bearing should be affected by you doing s-turns, next time you hear it, try doing some s-turns in your lane to see if the noise varies.

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They are new Michelin Energy tires. I had thought about rotating them to see if that helped. The are brand new though...or at least very lightly used take-offs. I dunno...I'll let the dealer decide what to do.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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Slight update:

I dropped the car off Tuesday night and I hadn't heard back so I "popped in" on my way home from work tonight and actually spoke to the technician. He has driven the car with a few different other guys there and they all agree it's coming from the right rear (and I agree too, after we both went for a ride together). He didn't seem to want to commit to anything while we were riding in the car (in terms of replacement parts) because they apparently haven't decided what it is at the moment. He has a feeling that it's tire noise. He said after we got back, he would rotate the tires and see if the noise moved. I tried talking him into replacing the bearing if the tire rotation didn't solve it, but he didn't really agree to anything on the spot. He said if the tire rotation didn't help, he'd have to talk to his group manager about what to do next.

I said I didn't want to rush them at all, but the car had already been there for two days and that if we still didn't know anything tomorrow that I'd need a more definite idea from them what the path forward is. He was talking about trying to swap the hub assemblies left and right, if that was possible, to see if the noise moved around. That makes me leery...just replace the dang bearing before going to all that work. Probably much quicker and cheaper for them...

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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He was talking about trying to swap the hub assemblies left and right, if that was possible, to see if the noise moved around. That makes me leery...just replace the dang bearing before going to all that work. Probably much quicker and cheaper for them...

Jason,

That's called "easter-egg troubleshooting". As the owner you should be the one who ca authorize that because now a known good are of the car is being disturbed? What happens if something goes wrong (and it's always a possibility, remember ... Murphy is an optimist)? If you feel they're a good dealer then all is well (my Cadillac dealer has always treated me well) otherwise I'd be skeptical.

Jim

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There was a voice mail on my machine at work that the car is ready. So I'll find out this evening what they did, and if it's fixed.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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Turns out he rotated the tires and claimed the noise was gone. I was slightly skeptical, but sure 'nuff, no more noise. I thought that odd. The service manager said, "not really, wear patterns can develop in tires, etc." I said I've often had some tire noise after rotating the tires, but it was a constant noise, increasing in pitch usually as speed increases, etc. I've never had a tire noise that came about ONLY at a certain speed.

Either way, she's quiet as a cat.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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She got a bath today and we enjoyed some open air cruising (70 outside today). There's not much that tops the feeling of riding around in a clean Cadillac.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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