DrRocky12

I purchased a "Certified pre-owned" 2012 RX450h. Love the car, it's me second Lexus. I have been to 3 dealers with my issue, with no resolve. Haven't seen this issue in the forum yet. It is an intermittent problem. When I apply the brakes, I sometimes hear a scraping sound --like metal sliding on metal. It could be a panic stop in traffic, backing out of the driveway, or going over a speed hump at 6 mph. The dealers have told me its not in the brakes per se. It seems to happen more frequently when the outside temperature is below 60 degrees. Of course it won't do it when the dealer drives it around the block. One dealer told me it was the sound of the electric motors--but I didn't hear that sound the first 15,000 miles I drove the car! Another dealer told me it was noise from the new tires--yet I heard it before I installed the new tires!! The third dealer told me they didn't hear it test driving the car around the block so there is nothing they can do! I t started around 50,000 miles and is bugging me at 70,000 miles. It puzzles the dealer service department. I put on 2 new rear shocks, four new tires, and had the suspension looked at. Anyone else have this annoying mystery sound? Any seasoned owner/mechanic have any ideas? Help!!

GSteg

iTrader: (15)

Is it possible for you to get us an audio clip of the noise? Is the noise coming from the front or rear? Driver side or passenger?

DrRocky12

I have carried and used a tape recorder in the car for a week now. I have been unsuccessful in capturing the noise. I either have the radio, satellite or CD on and it won't capture the sound. I cannot tell if it is coming from the front or rear, but I think its the front. I don't feel it in the car itself, but I suspect that the car body is moving on the frame when I stop under certain conditions. It mostly happens when the outside temperature is cool and it is dry air outside. I discovered after I purchased the car that Lexus of Pembroke Pines did some body work on the right front before I purchased the car. It did not appear in the Carfax, or on the service records, but I got a look at it after I made the deal to purchase after I transferred ownership of the vehicle. The dealership replaced a damaged right front quarter panel due to an accident. It was not disclosed to me at the time--and it's "certified pre-owned" which means the car is in top condition (or so they say). I made the dealer reseal the right side passenger door bottom as they did not properly put it in place and the bottom of the door seal sagged.. They will do nothing further to help me.

vlad_a

Does this happen after it rains or after a car wash?
It might simply be pads scraping off rust from rotors, which would be absolutely normal.
In RXh, this may not happen right away as the vehicle drives off because the regenerative brakes does most of the braking until you have to do an emergency stop.

Htony

Change the drive mode to see if it makes difference. That is first thing I'd do.

DrRocky12

Thanks both of you guys. I don't see a difference after car wash or rain. I have tried all drive modes on this vehicle and it does the same. I have driven in ECO mode, regular mode, and sports mode (yes I realize that it is a hybrid). Doesn't seem to make a difference. I am not hard on the brakes. Only had one pad change on my 2001RX300 after over 100,000 miles. I have had 3 vehicles with disc brakes and know about the rust on the rotors issues and its not that. My Volvo with disc brakes squeaked so much that my friends all said they could hear me coming--by the brake sounds, so I know about the squeaking issue with disc brakes.!

SteveCraig

A few things come to mind, might be worth checking if you don't otherwise find the issue.
1- slides on the calipers are steel against steel that should be very well lubricated. They move every time you apply the brake pedal.Have a brake shop - or a dealer - pull the wheels & inspect.
2- the parking brake assembly is a small drum brake set-up located inside the hub on the read brake discs.These can get wet & rusty & seize up if not regularly used.
3- metallic brake pads on these cars may/may not have a steel indicator letting you know the pads are getting worn down & time to change.
4- many times you can pull the brakes apart & wash down with a brake cleaner solution. There may be a pocket of fine dust built up against "something " & that may be what you hear.

Brake issues are usually pretty easy to diagnose but you need the wheels pulled off to have a good look.

DrRocky12

Thanks for your suggestions. Next Saturday the 450h goes back to the dealership to find answers. I almost never use the parking brake, so we might be on to something there. Most of Florida is flat, so P is just fine to keep the vehicle in place. Thanks for the suggestions. DrRocky

Htony

I drive '15 450h. Being hybrid this vehicle's brake system is little different I believe. Hydraulic, propulsion motors working together. There may be some electronics
control system involved. Tech. should look at both side. If the problem can be duplicated all the time that will help. Transmission system come to mind as well apart
from brake system.

Droid13

I don't think you mentioned if the sound is continuous, or just a quick instantaneous noise when brakes are applied. You mentioned a suspicion that the body might be moving on the frame. I had a situation where when braking or accelerating I would near a metallic noise. Tightening all the frame bolts eliminated 95% of the noise, so I personally don't think it's far-fetched to consider the body is moving a bit on the frame.

DrRocky12

Thanks to all who have offered to help. I am overwhelmed at your care. I had the frame bolts tightened and I haven't heard the noise since. I am crossing my fingers that this will be it.

N4TECguy

The way the dealer fees are set up, you won't find one that's willing to help you. They charge a flat diagnosis fee and if they don't find an issue, they can't really charge for anything else. Hence, they are incentivized to spend as little time as possible on your car. This is also why they hate looking for squeaks and rattles. Lots of time spent with little billable hours.

You may be better off with an independent mechanic on this who can bill you for actual time spent. It will probably be pricey but if it's driving you batty, it might be worth it. I think you should start by looking on the back of the rotors - the face you can't see through the wheels. Check if there's any abnormal ruts or scars, which could come from a bent dust shield or maybe a trapped rock. Then maybe check the subframe bolts and see if there's any movement there. The RX is a unibody SUV so it shouldn't have true frame bolts to speak of.

Fpan87

Where are the frame bolts located? Can you take a few pictures ?