2010 Impreza Outback Sport "thump" - brand new

I am the owner of a brand new Impreza Outback Sport. I’ve got a noise issue which I’ve not been able to reproduce at the dealership (of course). After shifting out of reverse and into drive, all while going under 10 MPH, after driving forward about 12 ft. there is a clang/thump sound coming from the right rear of the vehicle, near the area of the wheel well or rear door. It comes from underneath the vehicle and I can feel a small vibration in the floor. The dealer had it on their lift for about 30 minutes. They inspected the struts, springs, etc. and report they cannot find anything faulty.

Any ideas what would cause such a noise when moving from reverse > drive? The sound from the driver’s seat is akin to someone lightly punching the upper part of the right/rear wheel well. There are only 1,200 miles on the vehicle and they state it’s still in the break-in period, but something still doesn’t seem right.

The comment about still being in the break-in period is a good one. You know that whatever is going on is in the shouldn’t-happen period. The problem may be in the rear drivetrain or the suspension system. Perhaps without the weight of the vehicle on the ground the trouble won’t occur on the lift. The trouble sounds like it could be a fairly expense problem to fix later on if they don’t find it now. The trouble should be noted down in case they don’t find the trouble and then you find out later on what it is. As a guess to the trouble I would think something in the suspension may be sticking and then releasing when going forward.

Make sure it is noted off.

I think subaru gave up on Limited Slip Differentials(LSD) on new Impreza’s except STI however have you confirmed the tire pressure is proper in all four tires? My 04 WRX (w/LSD) will clunk if pressure is low in a rear tire.

Based on your description, I believe that you are hearing the anti-lock braking system going through its self-test.

This normal phenomenon is supposed to take place when shifting into drive and driving about 10-12 feet. The noise/vibration of this self-test can be felt in both the brake pedal and the floor of the car. While the ABS pump is actually under the hood, a unit-body car will frequently telegraph noises from the actual place of origin, so that the noise can seem like it is coming from elsewhere.

Putting the car on a lift will not reveal anything abnormal if the car is simply doing something that is normal.

While this is my best guess, I have to ask another couple of questions in order to help me with this possible diagnosis:

Does it make this noise very briefly and just once each time that you put the car into Drive?
If the answer is yes, that pretty well confirms my theory. If the noise takes place for more than a brief moment and/or if it happens repeatedly each time that you shift into Drive, then that blows my theory to smithereens.

Is this your first car with ABS?

Have you read the section of the Owner’s Manual dealing with the ABS and its self-test?

Interesting theory, and thank you for being so concise.

  • Yes, only ONCE, right after it’s put into drive. It is very much audible from that left/rear of the vehicle though, as if something is “springing” back into place.
  • While this is my first car with ABS, I have two friends with newer, similar model Subarus (both Impreza 2.5i models) and they aren’t reporting the same issue. However, I haven’t confirmed that they have ABS. I assume they do.
  • I have not read that section on the self-test, but now I will.

I would hope the dealer would have thought of this possibility, but of course nothing is guaranteed.

It still however doesn’t seem like a “healthy” sound. Perhaps the Manual will reveal more…

“Yes, only ONCE, right after it’s put into drive. It is very much audible from that left/rear of the vehicle though, as if something is “springing” back into place.”

I am now more convinced than ever that you are hearing the ABS self-test.
Please read the ENTIRE Owner’s Manual as soon as you get a chance, but clearly you should begin with the section pertaining to the ABS and its self-test.

The reason why I strongly recommend reading the entire manual is because most problems that Subaru owners encounter as the car ages are the result of owner ignorance regarding proper operation and maintenance of the vehicle. Pay particular attention to the section on why you should not drive the car with a donut spare unless you insert the special fuse that disables the AWD mechanism. Those who don’t do this wind up paying big bucks for repairs.

Also, familiarize yourself with the maintenance schedule that is contained in a separate booklet. As but one example, it is VERY important to rotate your tires on the specified schedule, otherwise you will encounter the same expensive repairs referred to above.

Incidentally, first you told us that the noise was coming from the right rear, and now you are telling us that it is coming from the left rear. It is beginning to sound more and more like the noise is being telegraphed by the unit body from the actual place of origin!

It’s the right rear. Apologies for the confusion and typo. I have previously read most of the Owner’s Manual, and just re-read the bit on the ABS self test after your post. It does not state anything about having gone in reverse, then forward. It only mentions the self-test at the point of start up.

I should also add one other observation- I haven’t been able to reproduce it at the dealership, I suspect, because the car has been run for about 30 minutes at that point. So far the times I have been hearing it is after the car has been shut off for at least one hour, usually more. It’s just an observation. I can’t say that it’s a direct correlation yet.

Trust me–it does correlate.

On my Outback, the self-test manifests itself only after the car has sat for several hours.
I back out of my garage, put it into Drive, pull forward about 10-12 feet, and then I feel/hear the Thump–BRRRRRRRRAAAK of the ABS self-test for about 1 or 2 seconds. I will not hear it again until the car has sat for several hours and is put into Drive for the first time.

Edited to add:
Even though my ABS pump is located under the hood, the noise from the self-test is really non-directional. More than anything, it sounds like it is coming from underneath the car.

What you are hearing is normal.

I always agree with VDCdriver when it comes to Subaru advice, and he may be on the right track, but I’m puzzled by your original description of the sound as a “clang/thump.”

The “clang” part is what bothers me, and the further description of something “springing back into place” in a later post. Those don’t sound like ABS noises to me.

My Legacy never makes any ABS noise, but the ABS system on my Acura sometimes makes a distinct BRRRRRR (is that enough Rs?) that can be heard and felt in the car. I don’t know if it’s a self-test or the high pressure pump charging the system, but I know it’s the ABS. It happens on start-up, after the car has been sitting a day or two. There is, however, no clanging or springing noise.

I don’t think the ABS system should be making any clanging or springing noises.

Let me rephrase that. The ABS system should not be making any clanging or springing noises.

BRRRRRRR, yes. Clanging or springing, no.

Please answer this question: Do you apply the parking brake when you park your Impreza?

I do not apply the parking brake.

Is the ABS self test always after going from reverse to drive? I ask this because I always back into my driveway and pull forward when leaving. I have yet to notice any real noise in my Mazda when I leave in the morning or after work. Maybe it’s because I’ve got my iPod playing(though not very loudly), but I’ve not heard any noises or felt any bumps when I put it in drive. I know just about the only new cars that don’t have ABS today are in the sub-$15k price range(Aveo, Yaris)

Edited :wink:

“Is the ABS self test always after going from reverse to drive?”

According to the Owner’s Manual for my particular vehicle, it is at “start up”. It does not mentioned drive or reverse.

Interesting about the self ABS test. I have owned three Subaru’s(although turbo) and never noticed any noise like that described not the self test.

With all due respect to VDCdriver, I’m not convinced this is the actual ABS self test. It various in loudness (it’s not uniform each time) and only comes from one side of the vehicle, nor does it fully match what’s described in the Owner’s Manual regarding the self test. It does not have a “staccato-like” sound as an ABS test would. It sounds more like a prong or spring clanging/thumping back into place. It may be related to the ABS self test system but, again, I’m not convinced that it’s the self-test itself.

At any rate, I greatly appreciate and value everyone’s input here.

If you really want to get to the bottom of this situation, you need to do the following:

Leave the car at the dealership overnight.
Go there the next day, and get a mechanic to accompany you to the car.
Make sure that there are are no extreme noise conditions nearby, like jackhammers, loud stereos, etc.
Start the car and do everything as you normally do, in order for him to hear exactly what you are hearing.
If he confirms that what you are hearing is not normal, hopefully he will have a fix in mind for the problem.
If he tells you that what you are hearing is normal, and if you are not satisfied with that explanation, then you need to contact Subaru of America. Contact info is in your Owner’s Manual.

After this situation is finally resolved–one way or another–please come back to this same thread to report the outcome. Bookmark it, or you may not be able to find it after a few days have elapsed.

Our Saturn Vue always has a thump after the first few feet of driving… sounds like someone bouncing a basketball off the rear quarter panel precisely three times. We brought it into the dealer and it is was a system of some sort but not the ABS… I’m sorry that I can’t remember what it was but maybe your Suburu has a similar thing? We also couldn’t get it to occur after driving it over to the shop, but they kept it overnight and when they started it up in the morning and drove it a few feet they heard it immediately.

This is, in a nutshell, precisely what’s happening with the exception of three times. I’m only hearing it once.

I am able to get it to occur after at least one hour. I think I will make another appointment and camp out for a while this time around. Believe me, I am eager to report back on any fix!

If you have any way of checking your service records I would LOVE to hear about what the fix was, if it was an actual fix and not something you’re living with. It might greatly assist in diagnosing my vehicle.

After reading jasendorf’s post, I had another thought regarding the problem!

If the noise is indeed coming from the right rear fender area–which is also where the gas filler is located–it is possible that the noise is a wonky purge valve in the evaporative emissions system. Truthfully, I have never heard a noise like this from the evap system, but I guess that anything is possible.