I need some insight here. I did a total brake job on the '99 this fall including new rotors, pads, lugs, fluid, sensors, and lines. I reused the caliper spring clips, pins, and pad dampeners. Ever since I completed the repairs, I get "clunk" noises from what seems to be most if not all 4 of the brakes whenever the car moves for the first time after having sat for a few hours.

At first I thought it might be caliper piston retraction, but I've verified that the pads are still sitting flush on the rotor faces. I've speculated that I should probably consider replacing the caliper spring clips as their age is unknown. But I just went to check the pad seating on the rotors and noticed that the hole on each brake pad (that the caliper spring clip pin goes through) is about 1/8" bigger than the pin itself. The pins all fit perfectly into their respect guide hole on each caliper so the pin sizing is correct. I don't recall how big these guide holes were on the old brakes. Can anyone offer insight to my problem? I imagine the pads are floating a bit in the caliper because of this larger hole on each pad.

 

 

Is the car wet at all (or even just in a humid environment) when you park? It's very common for the pads to rust to the rotors overnight if it's AT ALL moist. They'll then "break free" when you first move the car, making a clunking noise. Perhaps your new pad/rotor combo love each other more than the old set did, and are more prone to becoming one overnight.

If it's clunking only after sitting for many hours, I wouldn't worry. If it clunks every time you leave from a stoplight, something is wrong.

The fit of the retaining pin shouldn't really affect the positioning of the pad in the rotational direction or inward on the radius; those directions are controlled by the pad backing plate riding on the caliper. All the pin does is prevent the pads from moving outward along the radius and falling out of the caliper.

 

No rust or corrosion on the rotor surfaces. Car does it when it's bone dry. It really does make me think that maybe the spring clips are simply weak from age?....

 

When you say "spring clips" what do you mean? The cotter pin that goes through the retaining pin? Or do you mean the dampers that go behind the pads and into the piston recesses? I've removed those from my car entirely and can sense zero difference, so I'd suggest removing all those if you think those could be the source of the noise.

The retaining pin and cotter pin shouldn't really be able to "weaken" with age. If they are not all rusty and falling apart, they're fine. All they do is hold the pads from jumping out of the caliper.

 

The spring clips are what keep pressure on the pads against the pin.

The silver pieces in this pic:

 

Ah, yes. I supposed it's possible those are worn out, but I'd be surprised. Mine were totally rusty and gross-looking so I bought new ones, but the new ones weren't really any stiffer; just prettier.

 

I think he is referring to #15 in the diagram, the spring and retaining pin. I always replace those when I do a brake job. I agree about the pads sticking after a car wash or if they get soaking wet. When I back out of the garage after having washed the car the day before, I get a really good clunk from all four wheels. So sometimes I take the car for a short drive after washing and that seems to do the trick.
http://www.autoatlanta.com/porsche-p...section=602-00

 

Replacement hardware is cheap from RockAuto:
https://www.rockauto.com/en/catalog/...dware+kit,1736

 

Akebono pads are known to klunk on BMWs due to the floating caliper design and the undersize of the back plate of Akebono pads. However 911s have an entirely different caliper design and as long as the pads fits into the slot, the retaining spring should wedge it against the caliper. I would suggest pulling the pads out and apply some hi-temperature grease where there is metal to metal contact. Use it sparingly to avoid getting it on the pad surface. If that doesn't help then the problem is similar to BMW application where the backing plate of Akebono pads are undersized. It is unfortunate because Akebono ceramic pads are very good and dust free for street driving, but the clunking noise although won't hurt performance is quite annoying.

 

 

I have a set of calipers on the bench with what I believe are Textar pads. There seems to be a snugger fit between pad/pin than shown in your pic but I'm dubious if that's the cause of you noise.

 

Not sure about the clunk, but the clips should always be replaced and lubricated every brake job.

 

I agree. I replace the clips and use Ate Plastilube or Dow Corning Molykote on the guide surfaces.

 

Disagree. It's just a spring. No need to replace it unless it's broken or near-broken. Certainly not on every pad change. Maybe once every 20 years or so to be conservative!