Lord...the bolt is loose or worn out? Can the threading of the caliper bracket wear out, causing the caliper to rattle?
You'd probably end up with a stuck pad.
I'm doubtful you have a rattling callipper. Brakes are pretty simple.
- Waved disks, may cause rattling / vibration, scrubbing noise. Usually rare but might happen with uneven pad wear and maintenance.
- Pad wear : brake fade, screaching noise, mooshy pedal
- Stuck piston on brake calipper : either no brakes on that side, more likely brake lock, followed by screaching noise and smoke
- Stuck slider / hardware / unlubbed : scrubbing or screeching or brake fade
The only ' rattling ' i'd see described as an intermittant noise is from a dust shield which usually desintegrates in a few years around here or simply ends up scrubbing against the disk or the caliper.
I'd lift the car, take off the wheel, spin the disk see what's up, inspect pad wear,
if you go further, take off the caliper, inspect slider, pins, disk, dust shield, see if you get movement from the piston when you apply brakes,
inspect bushings while you're at it, look for dry rot / loose ends in the suspension assembly,
broche à metal + brake cleaner then reapply propper lubrification, change necessary parts, torque to spec
Not a professional mechanic, so correct me if I'm wrong.
if you still get a knock / rattle, start thinking about down to up : wheel bearing, any end bushing, strut hardware, strut top plate.
