Brake knock when hitting brake fast.

[Erin]

So when on a clean road, regardless of speed (even walking speed), when I hit the brake pedal quickly, there is like a single thump.
This thump happens only when the car is moving, not at standstill.
When either wheel is off the ground and I put it in gear and hit the brake, no noise.
It is not a continuous thumping like a warped rotor, just a single one. Best I can describe the sound is like if you hit rubber against metal.

I have checked – Upper control arms (brand new anyways), lower ball joints, tie rod ends, sway bar linkages (new),
springs and shocks seem stable (prying with a bar or shaking by hand), steering is solid, brake calipers and brackets stable,
brake lines don’t seem to be moving around, axles solid, tires do not wobble in any direction,

Reason I am concerned is when ABS activates (icy roads tonight), that thump happens several times.
Am I overlooking something?

Topic

[Mike]

I\\\’ve been noticing this effect on all kinds of cars for years. Most cars do it, some don\\\’t. I\\\’ve never been asked to fix or officially address that problem though because most people never stab the brake pedal like that. I\\\’ve poked around many cars looking for something wrong but never found anything. I belive that sound comes from the minimal but often normal amount of slack/clearance between the caliper slide pins and their bores in pad brackets, but tends to happen if the pads are also a little loose in the bracket. You can normally grab a caliper and shake it and feel that little bit of inherent looseness. On many cars, you can hit the tire with it up on a lift like you\\\’re checking for general looseness and you\\\’ll hear the caliper rattle a little bit.

I have a 99 Accord which is similar to your Acura, I\’ll try to remember to stab the brakes a few times on the way to work this morning and let you know if my car does it.

EDIT: My car does not do it, but the brakes are original to when I bought it and they may be crusted up and seized tight. The front brakes and lower balljoints are whooped and I’m going to be doing them very soon, and I’ll take notice to see if it does it after when everything has been cleaned and freed up.

Also, I had this right in front of me this morning and figured I’d take a video to show you exactly what I was talking about:

http://youtu.be/5y7ioHeLca8

[Erin]

So basically nothing to be real concerned about if everything else seems OK?
With my Acura having only 264,000 miles, I cannot imagine anything being loose. 😆

My car also has ABS problems – sometimes works sometimes not. I already know what the problems likely are there
but not about to spend a fortune to repair it.

I was just trying to make sure the actual brake system wasn’t gonna give me the bird one day.

Still trying to come to terms with the fact that my car isn’t exactly brand new anymore.

[Ingvar]

Clean ABS sensors.
You do NOT have lower control arms? As those will make noise like this. You said you checked UPPER ones.

[Author]

Replies