Piston Slap: To Battle The Moonroof Rattle?

Sajeev Mehta
by Sajeev Mehta

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 sajeev@thetruthaboutcars.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.

Sajeev Mehta
Sajeev Mehta

More by Sajeev Mehta

Comments
Join the conversation
2 of 11 comments
  • Krhodes1 Krhodes1 on Oct 01, 2014

    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.

  • Wmba Wmba on Oct 01, 2014

    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.

  • EBFlex At the summer property putting boats in the water, leveling boat lifts, cleaning the lots for summer, etc. Typical cabin stuff in the most beautiful place on the planet
  • Lou_BC I've I spent the past few days in what we refer to as "the lower mainland". I see Tesla's everywhere and virtually every other brand of EV. I was in downtown Vancouver along side a Rivian R1T. A Rivian R1S came off as side street and was following it. I saw one other R1S. 18% of new vehicles in BC are EV'S. It tends to match what I saw out my windshield. I only saw 2 fullsized pickups. One was a cool '91 3/4 ton regular cab. I ran across 2 Tacoma's. Not many Jeeps. There were plenty of Porches, Mercedes, and BMW's. I saw 2 Aston Martin DBX707's. It's been fun car watching other than the stress of driving in big city urban traffic. I'd rather dodge 146,000 pound 9 axle logging trucks on one lane roads.
  • IBx1 Never got the appeal of these; it looks like there was a Soviet mandate to create a car with two doors and a roof that could be configured in different ways.
  • CAMeyer Considering how many voters will be voting for Trump because they remember that gas prices were low in 2020–never mind the pandemic—this seems like a wise move.
  • The Oracle Been out on the boat on Lake James (NC) and cooking up some hella good food here with friends at the lake place.
Next