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2001 Outback wagon, 4EAT
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Discussion Starter · #1 ·
Hi everyone. I've been lurking these forums since I bought my Outback a little over two years ago. Gotten some great advice. I've been searching for a while now and haven't found anyone having a problem quite like this, though. Here goes,

I have a 2001 OB wagon, 4EAT. Bought it with 115,xxx and now it has 139,xxx. It's been making a low, whump, whump, whump sound like it has a flat tire that seems to be coming from the front driver's side wheel. Pressure is normal in all four tires and the tires are maybe a year old with 75% tread left at least. When travelling in a straight line, the sound seems to start out around 30 mph and gets louder from there. At highway speeds its pretty loud. Oddly it seems to stop when turning, EXCEPT when turning left at low speed. It doesn't make the noise when turning right at low speed. The steering wheel is not shaking.

I first noticed it was making a noise on turning left slowly shortly after I bought the car 2 years ago, but didn't think much of it at the time because it wasn't really loud and it was only happening on low speed left turns. But two weeks ago I had the rack and pinion replaced (it was hemorrhaging ATF) and since then the noise has gotten a lot louder, and it's doing it while driving straight. I don't really suspect the power steering though since it steers just fine, isn't losing fluid or making any other noises besides the whump/thump sound. The CV bushings are torn but it's not a clicking noise like a bad CV joint or a grinding noise like a bad wheel bearing. The suspension isn't bouncing around like crazy either. I replaced the front rotors maybe 6 months ago so I doubt they're the problem. Aside from the noise, the car seems to drive and steer like it always has.

I am sort of worried about this though, because I don't want the axel to snap or have the wheel go flying off the car. I'm going on vacation in two weeks and am planning to put probably 500+ miles on the car. The brakes are low and I'm having all four pads replaced this weekend. Think that could have something to do with it?

Any ideas as to what this might be? Maybe a bent rim or a tire problem? Could it be the axel, or is it a tie rod or some other suspension part? And lastly, the big question, do you think it's safe to drive like this?
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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Is the sound the same coasting as under power? Is it in sync with tire rotation or engine speed?

it seems you know some axle boots are split or torn. I could certainly imagine them making a 'whump' noise depending on how they were cut.

I suppose, as a test, you could use some duct tape around the boots, then drive in such a way that the noise should be produced and see if there's an improvement.

After a drive, compare the temp of the hubs left to right side. Be careful touching the wheel - use a remote infrared therm if you have one. dragging brakes or maybe bad bearings may show a higher temp.

Also, be sure to triple check all your lugnuts and examine the each tire all the way around and across the entire tread for cuts/cords/belts showing. perhaps even rotate the tires front to back and monitor for a change.
 

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2001 Outback wagon, 4EAT
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Discussion Starter · #3 ·
Thanks for the advice,

Just checked the lug nuts. They were tight all around, so that's ruled out.

I was thinking of having the tires rotated when I get the brakes done tomorrow or Monday. I'll try the duct tape over the CV joints as well when it's light out tomorrow. If anyone else has any ideas I'd love to hear them.
 

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Discussion Starter · #4 ·
Also, forgot to mention, the noise happens primarily on acceleration at speed, but at low speed it's there when I'm off the gas. I can't remember if it's happening on braking or not. Think I'll go test it now actually.
 

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Discussion Starter · #5 ·
Ok, so I just tested it to try to give a slightly more accurate description of what's going on here. The noise is there whether my foot is on the gas or off it. It's a little hard to tell what's happening on acceleration since the AC belt is squealing (my mechanic told me my AC pulley is going) but it seems to be loudest when my foot is off the gas. The tempo of the noise seems to coincide with the speed of the wheels, because it gets slower/lower pitched as I slow down. It only really goes away upon harder braking. When my foot's just slightly on the brake it seems like maybe it gets a little quieter or lower pitched, but it's still there. Maybe that means something's loose in the brakes? As I said, it needs brakes, and in the last 3-4 days I've noticed some slight feedback from the brake pedal while I'm braking harder, though the brakes have never made anything like a squeal. I'm having the brakes done this weekend, so I'll see if that makes any difference.
 

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The initial description -- whump/thump -- made me think tire -- cupping or a separation in a belt. If it's a tire, as mentioned by others, a simple swap (rotate) with another wheel would narrow this down quickly -- move the suspected left front to the right front and see if the sound seems to move to the other side of the car.

However, I wouldn't discount the possibility of it being a wheel bearing, especially based on the description -- noise first noticed when turning left, not right, but now it is apparent when going straight, but still not when turning right. Grinding is only one possible sign of a bad bearing, and at that point it's more likely on it's last legs. There are many cases here where a bad bearing didn't sound like it was grinding but more of a hum or growl.

While it could be a bad CV joint I would think that would more likely be the same when turning right and left -- it's all the same to the joint.

Is the noise apparent outside the car, or only inside? Is it there when going really slowly? I wonder if you could have someone drive the car slowly while you walk alongside to see if you can better determine where the sound is coming from. (It's hard to be sure when listening from inside the car.)
 

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Discussion Starter · #7 ·
Sorry its taken so long to write back. Okay, so last weekend I had all four brakes and the rear rotors replaced (needed independent of this issue - I did the front rotors about 6 months ago). Also had the tires rotated and the wheel bearings checked, the shop said they were fine. And... the sound is still there.

The shop did say the front driver's side strut is blown. Do you think that could be making the noise? I have noticed that the sound seems to go away when driving up a steep hill.

Also, I tried driving (in a relatively safe, unoccupied area) with my head out the window. It seems to be louder inside the car.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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I suppose the tire could be bouncing, but everything I've read says that would lead to 'cupping' type wear and it seems your mechs found no problem on the tires.

You know you have a bad strut (or, you've been told. If they are original, they EASILY need replacing) so, I see no reason not to replace them if you plan to keep this car. Hopefully, the sound will be gone.

I'm gonna also suggest, a bushing may be bad. There are lower control arm/transverse link bushings that may be allowing too much movement. And forces on those would be different under accel than coasting. Perhaps made worse by a bad strut.
 

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Did you find a resolution?

I am having a similar thump coming from my front driver's side. The thump was there when I bought the car over a year ago. At the time I thought it was a tire and wasn't concerned. So after I bought it, I rotated the tires and it was still there. I checked my brakes, and replaced the bearing (I believe the bearing was bad). However, the thump is still there. Even when barely moving, I can still hear and feel it like clockwork on every wheel rotation. I am about to replace the axle, but I am doubtful that that would cause the problem. If you have a solution, I would greatly appreciate hearing it.

Thanks,
Michael
 

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Me too. This is EXACTLY my issue. Goes away when turning left, it's a right hand drive though, so the same. Bearings axles replaced, RH tie rod inner needs replacing. Drives perfectly otherwise. Mystery!
 

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FWIW it turned out to be my left inner tie rod. The boot had never been replaced and I'm assuming this is what was making the noise. All this after my mechanic swore blind it was tranny or front diff. $150. Fixed. Knew I was right!
 

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Solved. Front diff. $$$$, replacement tranny coming up. Probably caused many moons ago by another owner running irregular tyres and a generally worn out front end. We're around 200k country miles now. Murphy's Law, my luck.
 
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