OK - I have had this sunroof rattle thing going on on and off for quite a while now. I have tried all kinds of ideas, from putting rubber hose around rods in the linkage, to putting a length of rubber weather stripping in the trough under the wind deflector, and I thought all was well since the rattle stopped. Turns out, after a while, the rubber weather stripping compresses, and the tension in the mechanism is relieved, and the rattle comes back with a vengeance.
Today, after noticing the rattle was back to its former racket despite grease, rubber hose, and weather stripping, I pushed up on the sunroof panel to verify that that was for sure the cause of the noise. Frustrated, I decided to tilt the sunroof up because this always banishes the rattle since there is no slack or play in the mechanism in that position - just some added wind noise that is muted when I pull the shade closed (I know, I know - I bet many a 4Runner owner has soaked their headliner by accidentally leaving the panel in the up position in the rain, or worse, in the car wash). Stay with me though.
I then had an epiphany - if support at the rear of the panel while tilted up gets rid of the rattle, what if I started at the closed position and just tapped the tilt-up/close switch a little at a time until the support mechanism is just barely starting to raise the panel? I figured why not, and while watching the sunroof panel, I began tapping the tilt-up/close switch and watching the motion of the panel. Here is what I observed:
-At first, the panel begins to drop down at the back just a little at a time.
-At some point soon, with continued tiny taps on the tilt-up/close switch, the downward motion stopped, and then reversed as the tilt mechanism began to SUPPORT THE REAR OF THE PANEL, pushing it up towards the tilted up position.
-When the panel has been raised back up and is flush with the roof while in the tilt-up operation, it is firmly physically supported at the rear of the panel by the tilt-up mechanism, and is in the same position relative to the roof as it is when in the regular "closed" position.
I took it for a spin on some rough asphalt roads, over a couple railroad crossings, some potholes, and other places that I know always make the sunroof rattle at least a tiny bit even when I had effected other attempts at a fix, but absolutely no rattles from the sunroof this time because it is being rigidly held in place and supported by the tilt mechanism. Since I rarely open the sunroof, this will probably be my fix for now.
I expressed enthusiasm for other things I have tried that hushed the rattle, but that all ended up ceasing to be effective long term. I am skeptical with this solution too for now, but thought I would add this observation in my ongoing search to fix this issue.
The next step I am going to check into, if this particular position of the mechanism proves to be the key to finally banning the rattle completely and for good long term while keeping the sunroof 100% functional, will be to look at the position feedback circuits to see if it would be feasible to adjust them to make this position the new "home" position that it would automatically go to when closing the sunroof from either the tilt-up position or the fully open position. That would represent a better and more elegant solution than brute force jamming the mechanism with rubber hose / washers / weather stripping / rags etc., or having to tap the tilt-up/close switch every time the sunroof is opened and then closed. Those other solutions worked for me for a while, but they all ended up letting the sunroof go back to rattling.
I know I don't visit and pipe up on here as often as others do, but life gets in the way of things a lot of the time. I will keep coming back as I make progress.
If all else fails, and I end up being driven to distraction (no pun intended - well, maybe a little) by this rattle, I know of one 100% certain method to stop this noise: take denatured alcohol, and with the sunroof tilted up, clean the rubber gasket and metal surface the gasket seals to very well, let the alcohol dry, and then run a bead of clear GE Silicone II around the gasket, close the sunroof for the last time, and take the fuse out of the sunroof motor circuit. 0% functional, 100% silent. I hope to not have to resort to this sort of kludge, but I am not above it.
Comments to follow.