Folks,
I posted on this last August shortly after getting the IS 200. In my case an NCT (MOT) vehicle tester found wear in the caliper locating bolts. The (Toyota) dealer who supplied the car checked, tightened them as much as he could without stopping them from working and packed them with grease. The rattle stopped for all of 15 miles!
My car definitely has a rattle as opposed to a thud and it's reminiscent of the time I forgot to replace the anti-rattle clips on the front of my absolutely reliable, sorry I ever sold it, Citroen Xantia. When the Lexus was serviced in February, the brakes were "cleaned and serviced". Silence was restored for a good 4000 miles but the rattling has since returned. I have now decided to examine the brakes myself and look for weakening shims and springs. This may not be until next weekend but I will report back and photograph anything interesting such as gaps and the lack, or otherwise of Coppaslip.
I do wonder at the success reported by the replacement of shock absorbers because the brakes need to be dismantled, I think, in order to replace the shocks and this may make the problem go away for a while at least.
I say again, I'm hearing a rattle over rough surfaces not a thud as described by others.
Mike
The Bigger the Problem, The Bigger the Hammer