Looking for a little help here. I'm a car repair newbie, but need to save some money these days. I have a 1997 Legacy GL wagon 2.5 automatic - 122K. Two things. From the day we bought it at 65K it has had a small hesitation when accelerating. It is the same today as 50K ago. Not a terribly big deal really, but would be nice to get rid of it. Is this a common thing?

 

Now the bigger deal. I have a deep pulsing / whoomp, whoomp, whoomp (not whomp) noise coming from the front wheels (I think - I guess it could be anywhere up front). It generally sounds like a tire problem, but the tires only have 10K, and look fine. Frequency goes with RMP. At high speed it just sounds like terrible road noise, but when slower you can tell it is individual whoomps. Turning doesn't matter. Breaking doesn't seem to matter.

 

What's the deal?

Now the bigger deal. I have a deep pulsing / whoomp, whoomp, whoomp (not whomp) noise coming from the front wheels (I think - I guess it could be anywhere up front). It generally sounds like a tire problem, but the tires only have 10K, and look fine. Frequency goes with RMP. At high speed it just sounds like terrible road noise, but when slower you can tell it is individual whoomps. Turning doesn't matter. Breaking doesn't seem to matter.

 

What's the deal?

 

Maybe a bad wheel bearing...

I would think that if it was a tire problem, you'd feel some vibration in the steering wheel. (you didn't mention if it did)

Could be a CV joint issue too...

 

Advise on what you find...

No steering wheel vibration. Wouldn't a CV problem be mainly when turning? Turning doesn't affect the noise.

I'd look at the cv's closely for rips in their boots and such, and for rotational play between the axle and joints.

 

It sounds like a bearing. I'd try to rule out the CV joint first (without replacing it, of course.)

if it's AWD you need to inspect the ujoints in the driveshaft.

 

did it just come one day, or has it been getting worse for awhile?

Thanks for the suggestions! It has been getting worse over time - I'd say over the past two months. And, yes, it is AWD.

 

I guess I'll try to rule out the CV joint(s)...umm...how does one do that? And the u-joint?

 

Are these things a tool-challenged guy can do himself?

To check for bad u-joints:

 

Get a large pipe-wrench (one that will open wide enough to fit the outside diameter of the drive-shaft). Grip the drive shaft with the pipe-wrench and try to rotate it first one way then the other (with the transmission in gear, and the of course the handbrake on).

 

If you can see any movement across the u-joints, then the bearings may be shot.

 

You can also do this by hand, trying to rotate the drive-shaft. You may see some movement in the u-joints, but only if they are very loose, and completely shot. Best to put torque on the drive-shaft with a pipe wrench.

even better to remove the driveshaft entirely. only requires 6 bolts on my subaru XT6, very easy to do. remove it and check all the joints. a bad ujoint will either be seized or feel very lumpy. they will fail and i wouldn't like to see what happens if they fail at 50 or more miles an hour.

 

on my XT6 all you do is remove 4 10mm bolts where it bolts to the rear differential. then remove two bolts holding the center bearing in place. the drive shaft will slide out of the transmission and the entire thing will be setting there for you to look at. very simple.

Great. Thanks. I'll give it a shot.

Don't rule out the tires just because they are new. You could have a defective one. Rotate front to back and see if the problem follows the tire(s).

 

Is the acceleration problem when coming off idle (eg 600 to 1000 rpm) or mid way thru (~2000 to 3000 rpm)? If the former, probably carbon build up. If the latter, could be the knock sensor. Also, if you haven't already changed out the O2 sensor, it is probably time. It will aggrevate the carbon issue.

 

Commuter (97 OB, 2.5 auto)

Don't rule out the tires just because they are new. You could have a defective one. Rotate front to back and see if the problem follows the tire(s).

 

Is the acceleration problem when coming off idle (eg 600 to 1000 rpm) or mid way thru (~2000 to 3000 rpm)? If the former, probably carbon build up. If the latter, could be the knock sensor. Also, if you haven't already changed out the O2 sensor, it is probably time. It will aggrevate the carbon issue.

 

Commuter (97 OB, 2.5 auto)

 

Hmmm...possible tires even though new, eh? I'll get them switched front to back. Boy that would be nice.

 

The acc. problem is mostly at low RPM, so is there some easy "carbon clean out" thing? I haven't ever changed out the O2 sensor. The check engine light is on all the time (I have ignored it), so it could be pointing to that - although the acceleration problem started long before the check engine light came on and stayed on.

 

Thanks!

Hmmm...possible tires even though new, eh? I'll get them switched front to back. Boy that would be nice.

 

The acc. problem is mostly at low RPM, so is there some easy "carbon clean out" thing? I haven't ever changed out the O2 sensor. The check engine light is on all the time (I have ignored it), so it could be pointing to that - although the acceleration problem started long before the check engine light came on and stayed on.

 

Thanks!

Have a MotorVac treatment done. (There are similar treatments under different names.) It worked for me. The second time it happened a couple of years later, the O2 sensor was aggrevating the problem (making the car run even richer). After changing it, the problem cleared up considerably right away, then slowly disappeared over the next several weeks. Over the counter stuff isn't strong enough if your problem is this bad. However, once done, the occasional bottle of something, or tank of premium does help to keep it from reoccurring. Check your tailpipe. I noticed that mine was blacker than ususal. Afterwards, it went back to more of a dark tan color.

 

Commuter

i wouldn't like to see what happens if they fail at 50 or more miles an hour.

 

 

It's a **** your pants sort of excitement right there. Oh man. Ask how I know.

I had a noisy wheel and narrowed it to bearing or brakes, and it was a bad caliper. Brakes worked so I did not notice any pull. Good luck.

If Calvin is Calvin College, I have room in my home garage, tools galore, and a spankin' new Haynes manual. Even keys to a machine shop if it gets that bad. Fair warning, I just bought my Subaru and know few specifics about them.

If Calvin is Calvin College, I have room in my home garage, tools galore, and a spankin' new Haynes manual. Even keys to a machine shop if it gets that bad. Fair warning, I just bought my Subaru and know few specifics about them.

 

What a great offer! But, alas, its our favorite little imagination machine, Calvin of Calvin and Hobbes. Thanks anyways!

 

I'm taking my first shot at it this afternoon so hopefully I'll learn something.

Maybe a bad wheel bearing...

I would think that if it was a tire problem, you'd feel some vibration in the steering wheel. (you didn't mention if it did)

Could be a CV joint issue too...

 

Advise on what you find...

 

You got it, unverviking. I took it the tire place to rule out tires and the mech. there said "hub and bearing assembly," certainly drivers side, maybe both. Is this something I can fix myself with a little help from Chilton's or alldatadiy.com?

 

Thanks!