I'm a new member and don't normally frequent bulletin boards, but this post drew me in.
I bought my first LS in 1990, my second in 1994 and now have a '98 GS 400. I truly love the car, but a few months ago, the sunroof rattle surfaced and I too find it maddening. As an aside, I never experienced it on either of my prior LS models.
The noise seems to come from the right rear corner of the sunroof, but it's tough to localize, even with a passenger using a stethescope. Moving the cover closed only mutes it slightly. It persists with the sunroof in open, closed and tilt positions. It does seem to be sensitive to weather, but I can't determine whether it's temperature or moisture which affects it.
With some research, I learned that Lexus released a TSB on 12/3/99 on the subject of "moonroof creaking and popping". The TSB # is BO004-99. This resulted in a production change, presumably taking place on or about that date. This essentially involves R&R of the glass and adding a variety of felt washers and strips which come in an "interior noise kit" (P/N 08231-00801). The purpose seems to be to isolate the plastic garnish pieces from other hard surfaces. For post change production the fix was covered under warranty, which of course, does me no good.
I wouldn't tackle the job myself without a shop manual, which is price prohibitive for just one task. I do suspect that this is a plastics problem (weather sensitive), but don't know for sure. I shrink from the idea of taking it in to the dealer. Rattle fixes have wildly unpredictable results and price tags. Also, it isn't replicable all the time.
So I seem to be stuck, unless anyone out there has any other ideas...
