Thumping from left brake

[repenttokyo]

Friday I had Hawk HPS pads and new brembo rotors put on the front of my car. Over the weekend, the left brake started thumping rhythmically upon braking, and I could also feel it in my pedal. By monday, this had turned into a metal on metal sound, a clanging. I returned to my garage and I discovered that the bracket holding the caliper had a stripped bolt. I replaced the caliper with a rebuilt one and now the thumping has started again. Any ideas as to what is going on? This is at low speeds, high speeds, etc.

[Barney Paull-Edwards]

I suspect the disc(rotor) is touching the carrier,due to either dirt behind the rotor or loose bolt on the carrier, look for wear marks.

[repenttokyo]

forgive me, but I am a bit ignorant in this area. What exactly do you mean by the carrier?

[whiskychaser]

forgive me, but I am a bit ignorant in this area. What exactly do you mean by the carrier?

The carrier is the bit that you position the pads into before you slide the housing with the piston in over the top of them. Does sound like the disc is out of true - similar symptoms to a drum thats worn oval. Cant see that happening to a disc overnight though

[Ross]

Your old caliper may have been stuck causing the brake to drag and heat the rotor to the point that it warped.A slight drag is normal as the pads are always in LIGHT contact with the rotor. Check to see if the drag is even for the entire rotation of the disc. If one spot is catching the rotor is warped or something is attatched out of line as BPE stated.
I noticed your other posts regarding this job and am wondering if A: You are out "testing" the brakes in a harsh manner preventing them from bedding in properly. B: Why, if you had this done for you, aren't you back to the shop who performed the work?

[repenttokyo]

Your old caliper may have been stuck causing the brake to drag and heat the rotor to the point that it warped.A slight drag is normal as the pads are always in LIGHT contact with the rotor. Check to see if the drag is even for the entire rotation of the disc. If one spot is catching the rotor is warped or something is attatched out of line as BPE stated.
I noticed your other posts regarding this job and am wondering if A: You are out "testing" the brakes in a harsh manner preventing them from bedding in properly. B: Why, if you had this done for you, aren't you back to the shop who performed the work?

when I first got the car back after having the pads and rotors installed, I followed the break in procedure that came with the pads. I haven't really driven the car much at all in the intervening time - so no harsh driving, or even highway driving. I don't know as if the old caliper could have warped the rotor with only about 20 km of driving, but i suppose anything is possible - it just seems unlikely.

I did got back to the shop the first time this happened and they replaced the caliper for free. I am not able to leave my car with them indefinitely, so I am trying to figure out how to fix this problem myself - as replacing the caliper, while fixing the metallic clanging noise, has not seemed to fix the thumping noise that preceeded the clanging.

I normally do my brakes myself, but September has been a terrible month and I have not had the time to do so. Lesson learned, I suppose.

[DanDombrowski]

I've done a lot of 'pad slap' brake jobs in my time, and there's not much to them. If the shop replaced the caliper for free with no questions asked, I'm thinking that they may have known they did something wrong when they installed everything, but thats just a suspicion on my part.

[Ross]

If the caliper was replaced I'll assume it was stuck since you didn't mention any leaks.
A stuck caliper certainly will warp a rotor.
They rust inside the bores. Having the piston retracted to accomodate new pads could plausibly put the piston in a position where it would hang up even though it previously had not.
Check the rotor for runout like I descibed before. A large amount of warpage/runout will also cause the piston to be pushed into the bore causing your low or soft pedal.
If the rotor is warped make them replace it. Machining it will eliminate the runout but the thickness will be inconsistant making it predisposed to future warping.

[Barney Paull-Edwards]

The caliper won`t warp the rotor, the person applying the pressure will! In 20 miles its not likely unless its really dragging badly.Go back to shop and get them to check carrier bolts and turn the rotor to check alignment.

[repenttokyo]

The caliper was replaced because the bracket for the caliper had a completely stripped bolt and groove. A new bracket is 230$ from bmw plus 60 for the bolts so I went for a loaded rebuilt caliper for $100. The caliper moving was what was causing the metallic noise initially. When I say they replaced the caliper at no charge, what i meant was that I paid for the part, and no labour. It wasn't underhanded, I was with them for most of the steps of the process.

I went back today and they are going to turn the rotor tomorrow and check for warping, as that is their diagnosis as well. They will also disassemble the brake assembly to check for any weirdness.

I bought the rotors from BMA, so it's not the shop's fault if I received a bad rotor. I also brought them the pads and the brake fluid. I don't buy any parts in Canada if I can avoid it, the markup is incredible.