lexuspleus

Car: 2014 Lexus RX350 AWD with 62k miles, mostly highway.

Observation:

• Sometimes, when I release the parking brake, a metallic thunk sound is heard when the parking brake pedal is about 25% of the way back to the off position.This happens about 40% of the time. I don't know how else to describe the sound, and I don't know how the parking brake on this car works. But when I release the parking brake briskly, I hear that sound about 40% of the time.
• The sound is noticeable when I have the window rolled down.

How I use the parking brake:

1. Shift to neutral and hold the regular brake down.
2. Push in the parking brake pedal all the way.
3. Release the regular brake pedal.
4. Shift transmission to park.

Other notes:

• I use the parking brake on this car regularly. When I park, I use the parking brake. I've taken Scotty Kilmer's advice on how to save the parking pawl mechanism in the transmission.

Question: Is that sound normal? If it's not normal, how should I fix it?

salimshah

We will be shooting in the dark and making wild guesses as to the source of the sound.

It would take 2 people, one to engage and release the auxiliary bake and the second to crawl under and see/feel what is causing the noise. It can be a simple thing as adjustment or lube.

Yes, I would definitely have it looked at or investigated. If the sound is there, there might be metal to metal rub and with exposure to elements rust can set in.

Salim

iolmaster

iTrader: (1)

The parking brake is nothing more than the old style drum brake system. It has shoes, retaining clips,hold down springs and a mechanical adjuster. It is far more complicated than disc brakes. Every time you put it on the shoe moves to engage the drum. Depending on how well adjusted the shoe is it could be traveling a fair distance and creating a noise. These are not hydraulic activated like the disc brakes. It could be the cable between the pedal and the brake mechanism. When we used to do drum brakes all the time we lubricated the interface between the shoe and the backing plate with Lubriplate. This was a common cause of noise complaints when we all had drum brakes. Remember, the entire system is mechanical. There are a number of places that could cause a noise. If it is all working well I suspect the shoes need to be lubricated where they meet the backing plate. Also, these things get out of adjustment all the time. Even though they are supposed to self adjust. They are easy to adjust. Have it adjusted and see if that helps.

salimshah

Sorry for going off topic ..
I was corrected by members that the fist gen rear drums (parking-brakes) are not self adjusting. I have worked with other drum brakes and simple panel mechanism is there to self adjust the star nut. Please confirm that the 3rd gen has self adjusting drums.

Salim

iolmaster

iTrader: (1)

I do know that the second gen RX has the star nut since I just rebuilt my daughter's parking brake. I assumed the third gen had it also. I know my 06 SC has the star nut. Both her RX and my SC are Japan built. Even if they have the self adjuster I always manually adjust mine anyway. Even in the old days when we all had drum brakes those self adjusters never worked as advertised. I never count on it.

lexuspleus

I thought the RX had discs on all 4 (I see discs on all 4).

Does the parking brake activate all 4 brakes or just some of them?

Does pushing down the parking brake lever merely push the disc brake pistons?

The cracking sound seems to be coming from the front left wheel area or around the wheel well.

Where do I look first?

If I want to see what the parking brake foot lever is connected to, what do I do? Which trim pieces do I need to take out?

iolmaster

iTrader: (1)

The parking brake does not activate any of the four wheels' brakes. It is a stand alone system on the rear only. The parking brakes are inside the rotor of the rear brake system. So, if the sound is coming from the front it has nothing to do with the parking brake. I suspect that you only think it is coming from the front. Sounds are difficult to localize unless you are outside the car.

lexuspleus

So I have an update on this.

As it turns out, the sound only happens when releasing the parking brake and the car is pointed nose downhill (i.e. release parking brake would cause car to roll forward)
It does not happen when releasing the parking brake while the car is pointed nose uphill (i.e. releasing parking brake would cause car to roll backward)

Interesting. Maybe this rings a bell to an expert mechanic here.

Nad1370

I'd say normal for it to make noise once in a while.
Noise you're probably hearing is the shoe pads releasing from the drum. (sometimes they do stick)
If i really want to get my hands dirty, id sand down the shoes (sand paper) just to get any contamination off the surface area.
Make sure the drum of the rotor are free of hot spots or rust.
Adjust both sides evenly.
I usually crank it down till it wont rotate.
Then back off an 1/8-1/4 of a turn.
Maybe even apply a little lube where the shoe pads contact the backing plate.