Hi All,

Looking for some input from whomever that may had experienced the same thing before.
Recently I started noticing that sometime when I apply the brake, a single clonk noise can be heard and also felt through the brake pedal (very light). It only happen once per deceleration. And this noise come and go seemingly randomly.

I been trying to troubleshoot myself and have not figure out the reason yet. Here are all the scenario I tried (Each scenario I tried at least 5 times):
1. Light braking from 40km/h to 10km/h. One clonk at 25-28km/h.
2. Normal braking from 60km/h to 10km/h. One clonk at 25-28km/h.
3. Hard braking (wheel did not lock by ABS) from 60km/h to stop. No clonk.
4. Hard braking (wheel locked by ABS) from 40km/h to stop. No clonk.
5. Light braking from 20km/h to 10km/h. No clonk.
6. Normal braking from 20km/h to stop. No clonk.
7. #1 to #6 was all done with the car set in Auto shift mode.
8. Manual shift mode then set to 2nd gear. 40km/h to 10km/h without braking (engine brake). No clonk
9. Manual shift mode then set to 3rd gear. 60km/h to 10km/h without braking (engine brake). No clonk

The noise sounds like solid metal knocking on solid metal. It sounds more like a something hitting the suspension arm (just figuratively speaking) or anything in that vicinity. Definitely not brake squeaking nor a loose hose.
What is confusing me is when there is noise, the noise always happens when the car is under braking and clonk around 25-28km/h. However, the noise will just completing goes away sometime. I would have thought if it was something loose, it would always be there.
I am leaning towards something mechanical that kicks in when the car is around that speed. Or only activate when the speed is above 25hm/h. And maybe when it activates, it generate that noise.(due to a worn out/ corroded seal or part). However, I don't know what is activating at that speed.


ps. I also previously had a small issue where my brake pedal will be very hard the next day morning after the car is parked for the night. Already tried changing the booster valve and did not solve the issue. The brake pads are after market that was changed by the previous owner so I have no idea what they are but definitely still have plenty of thickness left. Not sure if this have anything to do with the noise.

Please let me know if you had similar experience before or have suggestion on what else I can test to limit all the possibility.

Thanks in advance!

 

Dont know if its the same thing. I have a slight clunk type noise when braking at very slow speed, right before coming to a complete stop. I checked and concluded its the rear pads moving around because of worn clips. Not worried about it until it needs rear pads replaced

 

Thanks for the reply.
I did in fact been hearing brake squeak for a while but both Lexus and private shop had measured my pads and concluded the pads still have plenty of thickness left. Both of them said it is probably the pads compound causing the squeaking noise. Maybe it is possible that the clip is worn which caused the squeaking AND the clonking noise?!

 

Had a noise as described under equivalent circumstances. Removed pads, cleaned all components, applied correct brake lube compound as per FSM, noise remediated.

 

I have observed something similar. I occasionally hear a "greeeeek" sound and feel something shift slightly in the brake pedal. I took it to a mechanic and we noticed that a pad retention pin on the left front caliper had slipped axially about 0.25in. (The pin is tapered, so there is little danger of it slipping out entirely.) He tapped the pin back in with a mallet, and the sound disappeared until I got into stop-n-go city traffic some 50miles later.

The brakes are powerful, consistent, and work well. The pads have plenty of meat on them, and the sound and feel is not like a "pad slap" clunk sometimes caused by sticking calipers. My mechanic observed the pins and spring were worn, and advised me to replace the brake hardware kit (04947-0W010) at the next pad/rotor change. I might do the replacement early to see if it resolves the issue, but at this point it seems to be just a nuisance.

Diagram of brake hardware kit at link below. The top pin had slipped on mine, the bottom one and the center bolt were fine.
https://www.lexuspartsnow.com/parts/...947-0w010.html

 

Thanks for the info.
Over the weekend I asked my wife to drive the car while I was outside the car listening. I thought that if it was indeed the pad slapping like everyone is talking about, I must be able to hear it louder outside the car and pinpoint the noise to around the brakes.
And you know what? It was the brake!
The noise was so loud that I am surprised that none of the pedestrian had been staring at me when that happened around them.

Now that we found the issue thanks to everyone's help, do I need the brake hardware kit or is it the brake piston needs to be cleaned? I should be able to change the hardware kits but taking apart the caliper to clean the piston might be a little more challenging. (Never done either before).

Lastly, while my wife and I was out there testing, the rear brake also clonked once. I might decide to just change the parts for both front and rear. Is the part number you provided for both front and rear?

Thanks!

 

Glad you could narrow it down. I have a bit of experience servicing pins, boots, and pistons on sliding calipers...but unfortunately no experience with monoblock/fixed calipers and opposed pistons. My plan was to get in there, take the pads out, check the pad shims, check the piston boots, and then replace the hardware kits upon re-assembly.

Hopefully others here can chime in with their experience.

Note that rear brake hardware (aka "fitting") kit is a different part number (04948-0W010).
https://www.lexuspartsnow.com/parts/...948-0w010.html

 

Photos of referenced parts...

Front.

Rear.