2024 RX 350h rear left brake disc blazing hot

[everestto]

I bought the 2024 RX 350h and have been driving it regularly for about a year now and without issues. I recently observed that after each trip, that the rear left (driver's side) brake disc is extremely hot while the rest 3 are cold. The 2 front brakes are consistently cold like they were never used. The rear right is cold though not as cold as the front. I could feel the other 2 with the back of my finger with confidence but was scorched when I touched the rear left (the hot one).
The rear left is so hot that even the rim is hot too and I could feel the heat radiation if wearing shorts and walking past. I rely a lot on regen to slow my vehicle so I rarely brake and never into shock braking so don't expect this extent of heat on my brakes.
Curious why that is and I asked ChatGPT for possible answers and it came up with this:
"The RX 350 hybrid uses the front wheels for regen and rarely applies the friction brakes to the front. EBD (electronic brake force distribution) is why it might apply more braking force to one rear wheel over the other". While I agree with AI on this explanation, the degree of temperature difference between the 2 rear whiles is to the extreme: one too hot and the other too cold. And why is one wheel consistently the hot one. I tried some tests by having my wife and my daughter occupy the passenger sides to increase weight on that side but the result is still the same: the driver's side rear disc extremely hot.
I took it to the dealership and they said they believe the car is working normal if there are no lights in the dash indicating a fault.
Anyone else experiencing this?

[McBrian]

You have a caliper that is not releasing properly when you let off the brake. Weird, but still quite possible on something this new...

Slide pins need servicing or you have a failed/rusted caliper/piston that isn't relaxing pressure. Also a symptom of a parking brake not releasing due to corrosion/damage/cable binding.

Could be one or a combination of all of those. A visual inspection will undoubtedly find one or both of the pads dramatically more worn than the other.

If you've regularly got the pads and rotors that hot you should replace them (do both sides when you do it)

AI is only good to get you near the ballpark. Useless for real world solutions. Thank you for asking here.

[everestto]

You were spot on. The dealership fixed it.

Thank you

[RX400h06]

In hindsight:

You're not alone—this exact issue has been reported by other 2024 RX 350h owners, including one detailed post on the Lexus Owners Club forum. The symptoms match yours almost identically: rear left brake disc getting scorching hot, while the others remain cool, even after light driving with heavy reliance on regenerative braking.

While EBD and regen logic can explain some uneven brake usage, the extreme heat on just one wheel suggests a mechanical issue rather than normal hybrid behavior. Here are the most likely culprits:

1. Sticking or seized caliper: If the caliper piston or slide pins on the rear left are sticking, the brake pad may be dragging constantly, generating excessive heat.
2. Collapsed brake hose: Internally damaged hoses can act like a one-way valve—allowing pressure in but not releasing it, keeping the brake engaged.
3. Faulty parking brake actuator: If your RX has an electronic parking brake, a malfunctioning actuator could be partially engaging that wheel.
4. Uneven pad wear or warped rotor: These can cause constant contact and friction, even without pedal input.

The dealership’s “no warning light, no problem” stance is frustrating but not uncommon. Unfortunately, many brake issues don’t trigger fault codes. You might consider asking them to inspect the caliper, hose, and parking brake actuator directly, or even request a thermal imaging scan after a short drive to document the temperature imbalance.