09 Outback Sport - One "thump" sound from front passenger wheel whenstarting car

[Dan]

I have a brand new, '09 Outback Sport with an automatic transmission
and less than 1500 miles. I start the car, back up out of my parking
space, and put the car in drive. As soon as I start to depress the
accelerator, no matter how lightly, I hear a thump from the front
passenger wheel compartment. After that, I don't hear the sound again.
So I drive to work, park it for the day and, when I leave work to come
home, I hear the sound again, but only once. The same thing happens
the next day. I've been noticing this for about a week, and it seems
to happen every time.

The sound is loud enough to hear over soft music. I probably wouldn't
notice it with loud music. To me, it sounds like a large plastic flap
closing. I can't think of what part might make a sound like that. Any
idea what it could be? I plan to get it to a dealer to take a look at
it, but I'd like to see if I can figure out what it is. I'm also
wondering if I need to get it to a dealer right away, or if I can wait
a few days. Any advice / opinions are appreciated.

 

[Carl 1 Lucky Texan]

I have a brand new, '09 Outback Sport with an automatic transmission
and less than 1500 miles. I start the car, back up out of my parking
space, and put the car in drive. As soon as I start to depress the
accelerator, no matter how lightly, I hear a thump from the front
passenger wheel compartment. After that, I don't hear the sound again.
So I drive to work, park it for the day and, when I leave work to come
home, I hear the sound again, but only once. The same thing happens
the next day. I've been noticing this for about a week, and it seems
to happen every time.

The sound is loud enough to hear over soft music. I probably wouldn't
notice it with loud music. To me, it sounds like a large plastic flap
closing. I can't think of what part might make a sound like that. Any
idea what it could be? I plan to get it to a dealer to take a look at
it, but I'd like to see if I can figure out what it is. I'm also
wondering if I need to get it to a dealer right away, or if I can wait
a few days. Any advice / opinions are appreciated.

I think people sometimes experience a similar sound from brake pad
movement. I would definitely have it investigated thoroughly. Something
could have been overlooked in dealer prep. Loose lugnuts for instance.

And if they tell you "they all do that" point to one on the lot and ask
for it's keys.

Carl

 

[Clifford Heath]

I have a brand new, '09 Outback Sport with an automatic transmission
and less than 1500 miles. I start the car, back up out of my parking
space, and put the car in drive. As soon as I start to depress the
accelerator, no matter how lightly, I hear a thump from the front
passenger wheel compartment. After that, I don't hear the sound again.

Are you sure it happens after the car has been left idle? Not each time
after you've reversed, or have applied the brakes in reverse?

After you've applied torque in reverse, the suspension may have moved
on a loose point or coupling, which then thuds in the opposite motion
when you apply forward torque.

Same with braking in reverse, except it most likely affects the brake
caliper mountings, and the thud would come when you apply the brakes,
kinda as Carl said.

I suspect a loose suspension mounting. If you had a castor control arm,
possibly a worn bushing there - but struts don't have those. Possibly
a wishbone bearing?

If that's what it is, you'll need to disassemble it to be sure, as
the force applied by springs etc will prevent motion under normal
shop probing.

 

[Dano58]

I have a brand new, '09 Outback Sport with an automatic transmission
and less than 1500 miles. I start the car, back up out of my parking
space, and put the car in drive. As soon as I start to depress the
accelerator, no matter how lightly, I hear a thump from the front
passenger wheel compartment. After that, I don't hear the sound again.
So I drive to work, park it for the day and, when I leave work to come
home, I hear the sound again, but only once. The same thing happens
the next day. I've been noticing this for about a week, and it seems
to happen every time.

The sound is loud enough to hear over soft music. I probably wouldn't
notice it with loud music. To me, it sounds like a large plastic flap
closing. I can't think of what part might make a sound like that. Any
idea what it could be? I plan to get it to a dealer to take a look at
it, but I'd like to see if I can figure out what it is. I'm also
wondering if I need to get it to a dealer right away, or if I can wait
a few days. Any advice / opinions are appreciated.

It COULD be the ABS system recycling. It typically does that every
time you start and drive the car. In some cars, like my Audi, it's a
'crunch' sound, in others, like my Odyssey, a 'slap' sound..... Take a
look in the Owner's Manual and see if it mentions any sort of sound
that you might be related to the ABS system.

Dan D
'99 Impreza 2.5 RS (son's)
Central NJ USA

 

[Dan]

Are you sure it happens after the car has been left idle? Not each time

after you've reversed, or have applied the brakes in reverse?

It only seems to happen once per journey. It doesn't happen while
idling or reversing. If I leave it in park or neutral and rev the
engine, it doesn't happen. It only seems to happen when I start moving
forward. And once it happens, it doesn't happen again. I have gone
back and forth a couple of times, but only gotten it to happen the
first time forward.

Given what Dano58 said, I'm going to try starting, pulling out,
parking, TURNING THE CAR OFF, and starting again from ignition. If it
is related to the ABS startup sequence, I would expect to hear the
sound again.

Thanks for the tip about the suspension mounting. If I can't get a
good diagnosis, I'll ask the mechanic to consider this. I'd be
surprised if I have a worn bushing at this point (<1200 miles), but
maybe a bad one to start with.

 

[bugalugs]

It only seems to happen once per journey. It doesn't happen while
idling or reversing. If I leave it in park or neutral and rev the
engine, it doesn't happen. It only seems to happen when I start moving
forward. And once it happens, it doesn't happen again. I have gone
back and forth a couple of times, but only gotten it to happen the
first time forward.

Given what Dano58 said, I'm going to try starting, pulling out,
parking, TURNING THE CAR OFF, and starting again from ignition. If it
is related to the ABS startup sequence, I would expect to hear the
sound again.

Thanks for the tip about the suspension mounting. If I can't get a
good diagnosis, I'll ask the mechanic to consider this. I'd be
surprised if I have a worn bushing at this point (<1200 miles), but
maybe a bad one to start with.

One test you could do is to reverse (don't just roll backwards) and
apply the brakes firmly. Then drive forward.

 

[S.Hansen]

There have been other cars-Outback's I believe, that have had this issue. It
was brought up in a training class and even the instructor's car. I don't
think they have officially found a cause or issued a TSB on it yet. Believe
me, those of us in the shops WANT accurate instructions reguarding issues
such as these-
I'll look around the Subaru net for any new info
Steve

 

[Hachiroku $B%O%A%m%/(B]

There have been other cars-Outback's I believe, that have had this issue. It
was brought up in a training class and even the instructor's car. I don't
think they have officially found a cause or issued a TSB on it yet. Believe
me, those of us in the shops WANT accurate instructions reguarding issues
such as these-
I'll look around the Subaru net for any new info
Steve

Not a sticky caliper, eh?

Does Subaru still put the parking brake on the front wheels? I'd be having
a look at that, although it seems that someone at Subaru would have
investigate that already.

I would suggest to the OP that he try to not use the parking brake for a
few days and see if it stops...

 

[S.Hansen]

Not a sticky caliper, eh?

Does Subaru still put the parking brake on the front wheels? I'd be having
a look at that, although it seems that someone at Subaru would have
investigate that already.

I would suggest to the OP that he try to not use the parking brake for a
few days and see if it stops...

No, brakes are in the rear now- where they belong.

I'm thinking it may have been (talk around the water cooler) a strut issue,
but can't find any info on it. Am back in school mid april, will ask the
instructor.