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Medium Pitched Tone Above 20 Mph


amcdonal86

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Finally I am having an issue with my LS400 after about 15k miles and 1 year. I'd say that's not bad!

There is a strange tone (almost like a whirring without the actual whir...) that seems to occur now above 15mph. The closest noise I can approximate it with is the sound of air rushing out of an exhaust fan outlet (like the exhaust outside coming from a clothes dryer). It seems to be drivetrain related.

Notes:

**The tone does not change pitch with increasing speed and does not appear to go away at higher speeds.

**Even if I shut off the engine at speed and cruise in neutral, the noise remains unchanged.

**The noise continues until I drop below about 15-20 mph.

What on earth could this noise be? I am thinking of changing the transmission fluid and see if that has any effect.

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Strange for sure. Since its not speed related I'd be inclined to check things unrelated to drive train first. If it were drive train I'd think there would be some RPM or vehicle speed correlation. A noisy blower fan? A tired fuel pump making noise?

Can you locate a direction or source its coming from? This may sound crazy but they make these mechanics stethoscopes for locating noise and pinpointing it. Maybe a few bucks on them will help you get a directional fix on it and better understand the source.

I had a car several years ago with a bearing to support the driveshaft midway. It started making noise but the ptich varied with speed. Since your doesn't vary it is puzzling.

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It's going to be impossible to use a stethoscope while the car is moving. I am not sure, but I FEEL like this noise happens more loudly when I am off the gas going downhill--perhaps when the drivetrain is doing some engine braking.

It's not a noisy blower fan, because I've shut off my A/C to check if that was the problem. I don't think it would be the fuel pump either, as I shut off the engine while driving the vehicle to see if there was any change in the noise (there was not).

At this point, I am not sure what to think. The car is parked under a tree, and tons of leaves are falling on it right now and seem to be getting into the air vents near the base of the windshield. Perhaps it could be something that simple.

I, too, am perplexed by the fact that the pitch does not change at all when the vehicle is moving at different speeds, so perhaps it is the wind blowing over the car or some strange leaf issues.

Thanks for the help, curiousB! I would welcome any more ideas/comments that anyone might still have!

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To me its sounds as if maybe something is getting caught by the wind as you ride. Wind related annoyances seem to pick up around 15-25mph i would guess. Try looking for a loose panel or cover that may have become dislodged or shifted under the car or hood.

Just my two cents! :whistles:

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Okay, well I did some more tests in an attempt to diagnose the noise. The noise, as I said, happens when moving above 20mph and happens whether or not the engine is on. I checked the tranny fluid level, it looks good (the color is okay--still a nice amber color) and power steering fluid level, engine oil, coolant, etc. All seem to be okay.

I cleared all the leaves from under the hood and at the base of the windshield.

I then went for a drive and continued to hear the same noise. It is incredibly strange. Then I did some hard turning maneuvers at above 20 mph. There was some rough-ish sounding noise when turning hard to the left and right, but I attribute this to normal tire noise. The noise continued at the same pitch throughout these maneuvers.

Then I started doing some hard braking tests. At 35 mph (the noise is occurring at this speed), I braked hard and reduced my speed to 20 mph within a second or two. The noise stops! However, 1 second or so later, when the car returns to its normal balance, the noise begins again at the same pitch and volume. It almost sounds like fluid isn't getting to a place it's supposed to get unless I brake hard.

It is very difficult to determine where the noise is coming from. I think I need to have someone else ride in the car with me and listen.

Does anyone have any idea what it could be?!

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Actually, what I did notice was that the passenger (right) rear wheel didn't seem to be locked by the parking brake. I wonder if the parking brake could be the culprit here.

EDIT--I don't think so because I just tried to drive the car and see if engaging the e-brake made any difference. It did not.

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Here's a thought. My wife's car (Lincoln Aviator) started making a ticking noise as you coasted along. Was the strangest thing, not affected by speed. Removed brake rotor/drums in rear and found the parking brake shoe had broken and the lining material came off the shoe and was bouncing around as chunks of friction material inside the drum. The rattling around of the material was creating the noise. Not the same symptoms as yours but maybe you need to pull a rear rotor and see if there is anything strange going on in there. The inner drum was severely corroded as well so replacing shoes only wasn’t an option, shoes, pads and rotors all new.

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