By on October 1, 2014


TTAC Commentator Sobro writes:

Hi Sajeev and your goateed evil twin Sanjeev!

Beige. We all know it, we all love it, especially when it comes in Lexus Pearl White as my wife’s 2003 ES 300 does. This vehicle has had exactly one non-maintenance item replaced since bought new: the A/C compressor relay. My wife installed it since her office is near the Toyota dealer. And it was July. In Nashville. It was my research in the Lexus forums which led to this fix for the flashing LED in the A/C button.

Which brings me to my question.

The sunroof has started to clunk occasionally when hitting bumps, and the clunk is directly overhead of the driver. This sort of thing drives me nuts, so I’m glad I don’t commute in the wife’s ride. The Lexus forums have very little to offer, and what they do tend to start with “remove the sunroof”. Any ideas? Thanks!

Long time lurker, first time caller!

Sajeev answers:

Take it from someone working on moonroofs for 10+ years, you almost always remove the glass to do anything. The forums seem scant on info on a cursory glance but–ZOMG R U SAYIN’ ME AND SANJEEV COULD BE DAVID HASSELHOFF?

Wait, that’s no goatee on Garth!  (sigh of relief)

So anyway, moonroof rattle: since you mention the glass itself opens/closes/seals like new (no wind leaks), I betcha the rattle comes from the shade or the wind deflector.  Rule out the shade by pressing your palm against the shade and drive over a road known to cause the rattle. Start with light pressure and use more if the rattle doesn’t go away, to ensure the shade can’t possibly mask another problem with the track.

I have my doubts about the shade, as most Lexus’ products have a rather heavy and rattle-resistant shade, adding weight to silence a rattle isn’t likely. The (often spring-loaded) wind deflector is my bet. But other problems could be at fault: judging by the Sunroof Doctor‘s comprehensive repair kit.

What’s the fix?  Get a factory shop manual (no exceptions) to ensure you don’t break anything.  I’d venture a guess, but I’d prefer to remain lawsuit free after you install it wrong and the moonroof launches itself on the highway.

Sanjeev answers:

Wait, wait: you think anyone cares enough to actually want to sue you?

I’m too busy growing a goatee now, otherwise I’d tell everyone about that time you didn’t install a moonroof correctly and it flew off the car. If only people knew The Truth About Sajeev


Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice. 

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11 Comments on “Piston Slap: To Battle The Moonroof Rattle?...”

  • avatar

    LOL, nice answer Sanjeev. An 11-year old Lexus does not signify deep pockets so I’m betting the farm you are correct in my case. Your brother’s pockets would deepen if only his obsession with rare Ford products waned.

    As for Sajeev’s reply, I’m thinking that after 11 years and 146,000 miles it’s time for me to visit the Flying Spaghetti Monster’s bookstore. The shade has already been tested and passed.

    I pulled the shade back and pressed on the driver’s rear corner of the glass and that stopped the rattle, if that helps with the diagnosis. And as an update to the near bulletproof beige, I can sadly announce that the upper motor mount was replaced shortly after contacting the brothers.

    • 0 avatar

      “I pulled the shade back and pressed on the driver’s rear corner of the glass and that stopped the rattle, if that helps with the diagnosis.”

      Well in that case…I suspect that either there’s a loose screw (the one that holds the glass to the arms) or the driver’s side arm is busted. Or the part of the frame that holds the arm. That repair kit should fix it.

  • avatar

    Excellent! Thanks. Of course the “Step 1, remove moonroof” is still in play. Yikes!

    • 0 avatar

      At least refitting it will be easy – the reverse of removal.

      Does anybody else it it when a manual says that? Haynes do that a lot. Aaarrrgghhhh!!!!

      • 0 avatar

        Yes. And I also blow out blood vessels when a manual says stuff like, “Remove engine per Chapter 1″….

        • 0 avatar

          +2 both situations are encountered daily. I do some manual writing as part of my job and truth be told it just makes life easier to refer to an already documented process this way. Its annoying to the reader but it is even worse to repeat yourself over and over. However this is also the difference between someone experienced in fixing such things and those new to the task.

      • 0 avatar


        But it is usually true. It goes back in exactly opposite the way it came out. If you have parts left over, you did it wrong.

        I love the super-murky photos, usually of a RHD car, when you are working on a LHD car, probably with a different engine and more crap in the way.

  • avatar

    Try cleaning the rubber seal around the glass and the body where the seal touches. A light application of rubber conditioner wouldn’t hurt either.

  • avatar

    Removing sunroofs is usually not particularly hard. Typically a couple screws on each side hold it to the mechanism, and it lifts right out. I’ve had a bunch of them out to replace seals and such over the years.

  • avatar

    One of the three rubber bumpers at the front that forces the glass to push up against the roof’s opening lip when closed fell out in my Subaru. Caused rattle.

    Opened roof to halfway position, did not notice rubber bumper missing. Closed roof, but it wouldn’t go all the way. Hmm. Noticed black object in well under roof at front, extricated it, placed in only hole available, closed roof, rattle gone. Siliconed bumper in place at trip’s end.

    You never know, might be as simple as that.

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