MASSMINI

Looking for help finding the source of a hollow knocking sound from the rear end of my 2001 RX (125K). I hear it almost all the time when starting from a stop or coming to a stop and it sounds like a loose marble in plastic container. I never hear it at speeds over 25 mph. It has irregular frequency that can vary between 2+ knocks per second and slower.
The following parts have been replaced within the last year:The noise sounds a bit like a rattling exhaust however I’ve shaken the exhaust with someone sitting in the drivers seat and could not reproduce it. I’ve also walked along outside the car as it was driven slowly and was unable to hear the noise from the outside (driver could hear it). It doesn’t matter whether I’m touching the brakes. Also, I’ve verified that the 4 large bolts mentioned by LexMex in another post are tight. All advice appreciated...

salimshah

I suggest start with simple things like looking under the rear hatch carpet. Loose tools and even the hook not held by velcro can be the source of noise. I woudl suggest take out the spare and examine the cavity.

Did you mention Awd?

If the Aux brake cable is loose, you can hear a clunk.

Salim

MASSMINI

I should have mentioned that the hatch area is empty and there is nothing loose in the spare tire area.

I'll take a look at the brake cable. Thanks.

Australian

Can you reproduce the sound out of gear. What have you eliminated so far?
https://www.clublexus.com/forums/rx-...mph-fixed.html
found this in 2nd gen forum is this anything like your experiencing?

MASSMINI

Yes. If I coast down a hill in neutral the noise is there.

It's not the rear stabilizer end links or stabilizer bushings (new last weekend)
It's not the exhaust.
Rear struts (KYB) and mounts (OEM) have 9K miles on them
Rear strut top bolts are tight.
Nothing loose in spare tire area
Bolts mentioned by LexMex in the thread below are tight.

MASSMINI

After a little quality time with my mechanics stethoscope and a floor jack I've isolated the sound to the headlight height control sensor mounted on the right rear control arm. It sounds like a spring slipping inside the sensor housing. From what I read the sensor is about $300 at a dealership but I can't find it on the Sewell site. Anyone know the part # and where it's available online? Or whether it can be fixed?

salimshah

Can you remove it and drive around without it to confirm that it is the source of problem.

Salim

carguy07

I think it is part # 89407-33020

Something like this: https://www.clublexus.com/forums/sc-...ng-system.html

MASSMINI

Thats it - Thank you!
Wow - $333 with the Sewell discount.
The search for used begins...

carguy07

Yea, that's ridiculous for what it is. The guy in that other post said that the ES uses the same part with a different bracket that can be switched over. These are only used on cars with the HID headlights. I don't see much there that would make noise though. Is there a linkage that goes to the arm on the sensor that might be the source instead of the sensor itself? Sort of like the tie rod looking part on ride height sensor?

http://www.ebay.com/itm/LEXUS-LS430-...26e276&vxp=mtr

salimshah

I am with carguy07 .. mechanical linkage should be the source of sound.

Salim

MASSMINI

I will take it out soon to determine exactly what is making the noise.
Question: If I have the sensor out for a few days do I need to temporarily level the headlights using the manual adjustment? And does that need to be undone once the sensor goes back in?

salimshah

If you allow me to speculate ... when you disconnect, you will get a warning light and the system will use default levelling.

I would not touch anything .. specially when you intend to put things back at the end.

Salim

MASSMINI

Update: With the sensor out I found that the main arm was not moving freely at all. I really had to push hard on the arm go get it to move by hand. Seems like the bearings inside the sensor are corroded and binding. As far as I can tell the sensor bearings were making a popping noise as the weight of the car causes the arm to move in small increments. And the noise seemed to be amplified by the suspension part where the sensor mounts. I could reproduce it easily lifting slowly with a floor jack. No corrosion visible inside the sensor, Lubing the heck out of it made it move a little more easily but still not as freely as I assume it would when new. I also insulated the sensor with a piece of rubber when I re-installed (see pic). It's almost entirely quiet now. Only sharp low speed height changes (like the end of a driveway) make any noise. And even that is much more faint than before. Done for now.