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

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

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.

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

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 (

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

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...

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.