Clunk/pop noise when depressing/letting up on brake pedal

heydanno · Post by **heydanno** » 15 Aug 2006, 19:32

Hi folks,

96 855 here, just over 100k, with brakes that are nearing the end of their lives (i.e. soon to be replaced).

My car has been exhibiting something a little unsettling, and I'd like to figure out what it is. When I put on the brakes, the car slows down fairly well, without a lot of pull (I think one of the rear calipers is partially frozen, and the rotor is pretty badly grooved so a little pull I can understand). What's bothering me is when coming to a full stop, the brake pedal will "clunk" right as the car stops moving. That is to say, it drops a tiny bit when right as the car stops, like something is a little loose and everything shifts just a little bit. A faint clunking noise also can be heard/felt. It's tough to describe, but I haven't experienced it in any other car. The steering is fairly loose (alignment needed?), though I don't know if the problems could be related at all. Any ideas?

Thanks!

Post by **MadeInJapan** » 15 Aug 2006, 20:33

Well, let's see....hmmm,
1. ABS system engaging?
2. The transmission shifting (bad motor mount(s))?
3. A loose caliper?
4. Steering rack clunk?
5. I don't know.

A visual inspection is probably needed

heydanno · Post by **heydanno** » 15 Aug 2006, 21:01

Thanks for the quick reply... some answers:

1. kinda doubt it's ABS; it doesn't feel the same way. This is more of a, um, clunk. I need to drive it tomorrow and really think about how to describe it.
2. not the transmission, it's a 5-speed.
3. caliper? intrigued. could this cause this?
4. steering rack? there is a very small hole in one of the steering rack boots and a tiny leak.

Post by **MadeInJapan** » 15 Aug 2006, 21:03

Could be a bad CV joint...sort of dout it but could be if all of the grease has leaked out....with it coming to a stop, the pressure on the joint is fairly intense, thus the clunk...does it go click, click when you're hard turning on the side with the hole?

Post by **pfeener** » 16 Aug 2006, 05:44

Change out your pads and rotors if they are deeply grooved and I'll bet it'll go away.

Post by **MadeInJapan** » 16 Aug 2006, 08:42

Ah....a voice of experience! I second that!
But like I said at first, a visual is probably needed.
Get down there and get dirty and SEE what's going on.

heydanno · Post by **heydanno** » 20 Aug 2006, 17:02

OK, thanks for the responses, guys... sorry for the delayed response, but here's some more info...

I did a bad job describing the problem, and I drove it some more, thinking about how to describe it better. The problem is more like the pedal pops up a little bit when removing your foot from the brake. It doesn't happen all the time, and actually it happens more often if you let up on the brake while the car is still moving. It's accompanied by a small clunk/pop/click noise just as you remove your foot. A similar noise sometimes occurs just as I'm putting my foot on the brake, too.

Re: the CV joints, I checked the boots last time I had it up on a lift and they were in good shape, though I didn't check the joints themselves. Also, there is some scoring on one of the rear rotors but the front rotors look good. Again, the click or clunking noise doesn't occur while I'm actively braking, just when I first depress the pedal and just as I let up on the pedal...

Thanks, and sorry for describing it so poorly the first time...

Post by **MadeInJapan** » 20 Aug 2006, 18:30

Now it's a clicking sound rather than a clunk and as you let off the brake. Are you sure it's not ABS...sure sounds like it when it takes over.

heydanno · Post by **heydanno** » 20 Aug 2006, 19:45

Hmm, maybe I shouldn't have dismissed ABS so quickly. Any suggestions on I can check to see if that's the problem? Would it require any kind of advanced equipment, or is it as simple as reading a code?

Thanks for the helpful replies, MadeInJapan.

Post by **pfeener** » 21 Aug 2006, 06:46

Very simple. Pull the fuse for the ABS unit and see if the symptom is still there.