microsup

@355F1 I noticed exact same. The temperature right now mostly above 90 and knocking gets out of control. Maybe I will schedule an appointment this weekend to show them the issue. I told them before like last fall, but temperature was falling down and knocking was not that easy to reproduce.
the noice coming from either storage compartment or rear trunk, definitely not from subframe like in a coupe.
and it sounds like something is bouncing either in the storage compartment or roof folding mechanism.
what interesting that it may knock even on a flar surface without any flexing.

355F1

I would recommend taking it in now to show them and have it filed.

I have a feeling that I will get a positive resolution after this visit--if not at least an explanation of why it is there. I just have a difficult time believing Lexus engineers designed this $100k+ vehicle to make a noise like this......

355F1

Can you try opening and closing your top a couple of cycles.

Once the tech did that he has not been able to replicate my knocking sound....they are keeping the car over the weekend but he just called me to let me know that it appears that cycling the top has taken the noise away.

Badhobz

Gents. I drove it last night with the top up and I’ve noticed that it seems to come from the rear quarter windows. So I used the all windows toggle next to the top controller toggle and dropped the rear quarter windows a smidge. It seems to have solved the click.

So to me that says it’s either the rubber / plastic that’s rubbing against the top. Or maybe I’m just deaf and I can’t hear it click when the top is down.

I will try and lubricate the top where the plastic / rubber meets the glass with this specialized silicone lubricant that s2000 owners swear by.

https://a.co/d/8QHPtf7

355F1

The knocking sound clearly comes from under the top in the middle and has nothing to do with my rear windows (I tried that many times)

Badhobz

did you try removing that wind deflector? could it be the wind deflector? mine sounds like its coming from the rear above the passenger side's ceiling.

microsup

that was my first idea. I removed wind deflector and it was no change. I can say that knocking sound comes way behind deflector. It sounds like storage compartment lid flexing and making that noice. And as higher temperature the louder the noise.

microsup

I scheduled my appointment for tomorrow, it should be 97 so I hope during test it will show that knocking sound.
meanwhile today I tried one more time to check what could bounce in a storage compartment and I noticed this.
attached video below. Make sure your audio is on.


there is also one area very close to rooftop mechanism, it is a plastic cover which makes click sound if you pull it one way, and only once, then you have to push it opposite direction, then pull it again and it will click. It is from driver side. Same cover from passenger side is dead silent. But it doesn’t make loud knock sound, and nothing would pull/push that thing.

the mechanism on a video, easily could make that sound when in motion, especially when roof closed and those arms could shake easy and may flex.
now question why temperature involved? Maybe because of the grease in that place, it becomes more liquidy and allows that metal pieces knocking.

i will show it tomorrow during my appointment.

Badhobz

good find!

however, mine sounds a bit more clicky? higher pitch..... uhhh not sure if its just the audio

microsup

A little update after 2 and a half days at dealer.

the noice still there. They check all possible scenarios what they could think of.
they check all the torque for rear suspension, checked the storage compartment, put some additional insulation. Nothing helped.

they gave up and proposed to take it to Lexus collision department to check body. I said pass, maybe if it gets to the next level I will consider it.

Brinylon

I still think the problem lies within the brace to B pillar connection. Lexus are aware of this phenomena (at least on coupes) and I, for one, would be all but certain the same problem exists on verts. I also suspect the inherent rigidity of the verts is a tad less than that of a coupe which may well exacerbate the problem. I think someone is going to have to bite the bullet and ask for Lexus to investigate what is now a known problem location and ask for the B pillar plate to be welded to the body of the car.

355F1

After 2 weeks at the dealer I picked up my car yesterday and the noise APPEARS to be almost 100% gone.

Their lead LC tech worked on it and even submitted a TSA case on it (this is the only way to get info like this relayed to engineering dept at Lexus in Japan.)--he had to have someone ride in side the trunk in the 110 degree heat to find the exact location of the sound.

It appears that the tonneau cover stryker/latch needed to be insulated and slightly adjusted (there is room to adjust it left/right as needed). He also readjusted and re-tourqued the rear support brace (which needs to be removed anyway to get to the stryker latch).

He drove 2 other LC verts that they had in the shop around their parking lot and the sound was evident on both although a different volumes.

I drove home yesterday and the sound of the knocking on turns/over bumps was all but gone and not even noticeable to someone who wasn't looking for it.

Only time will tell on this...my warranty will expire in just a couple months but at least we now have an answer to reduce this sound if it gets loud--and my gosh the knocking was extremely noticeable before he fixed it.

Kudos to Sloan @ Bell Lexus in Scottsdale for taking the time to get this fixed!!!

Badhobz

it would be very helpful if you were able to get pictures/videos of where this tonneau cover/striker latch is.

355F1

I didn't get any. You have to remove things (support brace/etc) to get to it, though.

It is literally the only thing that is connecting the tonneau cover to the body of the vehicle.

microsup

What is cover striker latch? If you look at my video, where I tried to shake those arms, those are not it right?
is it the latch mechanism of the compartment lid? And what brace you are talking about? The one inside storage the big one goes across the compartment with about 5 bolts on it?

if you would take some pictures and circle the area would be very helpful

thanks.