I have an odd knock caused by movement in my '09 (standard suspension with 71,000 miles on it..)
This knock only happens when I (1) backup a few feet and brake to stop then (2) move forward and press on the brake. When I step on the brake I near "knock.." from the front of the car. It's most noticeable with the top down. Top up - I don't hear it.
I may also (not really sure) feel something too. There are no other signs of anything funny with the suspension, no noises going down the road and my brakes are fairly worn (front rotors and pads will need attention before long). That's the only condition where I hear this knock (first noticed it in my garage some months ago..)
So it goes into my mechanic for an oil change in about 2 weeks, I'll be investigating more while it's up in the air. I'm interested in seeing what people think the noise is. I've had similar knock noises from disk brakes when the pads have a bit too much end clearance in the calipers and the anti-rattle spring gets old... but I've also heard similar noises from a bad suspension bushing.
What makes me guess the brakes first is they're pretty worn, the rotor has a healthy lip on it, and the pads are getting near where I expect to see the brake warning light turn on before long. When I bought the car, 20,000 miles ago I had all intentions of doing the brakes at that time, but they work perfectly so I left them alone.
Guesses? Theories I haven't thought of?
I think you're onto something given your description of the brakes. The fact you said you discovered it in the garage means you recreated the sound at a very low speed, that's a factor in my agreement. Unless it was a very faulty suspension component I do not think it would reveal itself in those conditions. Additionally, if worn to the point of making noise, the suspension piece would most likely present itself at speed during normal driving. That's especially true with a car that provides feedback of road feel with great precision. You also might see evidence of a suspension worn part in tread wear over time, so if your tires look uniform that also supports your brake theory. Most of the car's life is spent going forward, with the worn pads and rotors, perhaps a pad is monetarily chattering within the pad carrier from directional change. Big red
Brembos
have their own signature noises, they grunt differently with softly released brake pedal more than other OEM calipers when the grip force yields to motion.
Sounds like a pad is moving inside the caliper slightly and hitting the inside wall.
Possible that it's a bushing but sounds like front brakes to me.
I agree with your diagnosis.
I had my mechanic go through the suspension last time it was up on the lift and everything is fine with the suspension, so I'm inclined to agree with you. I'm suspecting a rear brake, since when it was on the lift he was replacing the front pads and rotors and the anti-rattle clips/springs... and he didn't note any loose pad issues.
I've decided it's part of the charm of the car and I'm ignoring it. I did install a louder radio so I can use the "Al Meski" suggestions for noises (a Volvo mechanic 50+ years ago) "Turn the radio up.."
