hfahmy

600 owners,

2008 LS600hl with 30K miles, when de-accelerate/brake I hear like jet engine slowing down sound, I think coming from the CVT/Electric motor area. Do you have similar experience?

caha14

This is interesting... Before I ask any other questions or speculate, if you brake with the car in neutral (i.e., effectively disengaging the hybrid drivetrain from the rest of the system), do you hear anything like this?

hfahmy

tried it this morning and I don't hear the sound when in neutral, only when I brake on D. I am thinking that this is the sound of the electric motor reverse charge to the hybrid battery when braking??

Vansibel

The way you describe it make the sound appear pretty loud, which shouldn't be. Did you just bought the car or does it started doing this recently ? A video with sound would help.

caha14

That's the thing. Regenerative braking would've been my guess, but it isn't super loud, and given that you've owned this car even longer than I (you're one of the folks I blame for my own upgrade :-) ), I'd imagine you would have noticed before. Has it gotten louder? One thing to do, fwiw, is to listen closely, as a pedestrian, the next time a Prius or other Toyota hybrid stops near you and compare. Separately, a video (as suggested) might help.

hfahmy

Sound is not loud. It did not go louder in the year I owned the car. I just want to make sure that there is a logical explanation to it. There are many things that are different about the 600 from the 460 and don't know what is and isn't normal.

One other area that annoys me is when the hybrid system runs low triggering a switch to gas, if I am in heavy traffic the car feels jittery and I feel some vibration until the hybrid system is back above 3 bars, then it is smooth again. Do you experience this?

Don't get me wrong, I still love the car and believe it is the best car Lexus ever made!

caha14

The noise does seem normal. You probably hadn't noticed as much before?

As far as the jittering goes, I don't know if it is the exact same issue, but I do feel it sometimes. In my case it seems less related to battery level and more to whether the system is "cold". Yes, it's annoying.

I do have an intermittent shudder when braking which feels like warped rotors (even though it isn't) and drives me nuts, as it damages what would otherwise be a perfectly smooth ride. Sometimes it's there; sometimes not, and it is unrelated to battery level, temperature or anything else I've been able to notice or measure. It's quite the mystery. Car is still awesome, though.

hfahmy

I also have the vibration when braking. I chased it a while ago, changed the pads and resurfaced the rotors and it is still there. Drives me nuts!

caha14

Is it intermittent for you like it is for me, or there all the time? It's definitely the regenerative braking. If I throw it in N and brake, it is smooth as glass (better be - my brakes are 12k miles young!).

hfahmy

Was not paying attention to braking when I put it on N. Let me try this again on the way home and will let you know.

sprtent

iTrader: (1)

I also think this is regen braking and is normal, unless the noise is loud. To further confirm, you can do couple things. Switch to the screen where charging is displayed and note if the noise and regen braking charging happen together. The other thing is find a small down slope and try put the car between neutral and drive (noise). Regen braking tends to get noisier with greater slopes.

Love to own an 600h someday. Had 2 Pri and 2 GS450h

hfahmy

So here is the verdict; when braking on N vs. D the following is observed:

1. No jet engine slowing noise
2. No braking shudder
3. Used to hear couple of clicks right before I stop that I thought either control arms or actuator, all gone!


So, can someone help me understand how can the regen cause braking shudder and/or clicking noise right before stop??

This is very interesting, the mystery of problematic pads/rotors is solved with another one

caha14

Some thoughts... In a nutshell, even though the brake pedal is involved in this whole episode, your brakes per se have nothing to do with these issues (putting aside any problems you might have had with your pads/rotors, which have now been addressed, as you've confirmed).


#1

When you are "braking" (and by that I mean stepping on the brake pedal or letting the car coast), the service brakes do not kick in until you are at very low speeds or in an emergency situation. Instead, as you are likely aware, one of the hybrid system's motors is used as a generator to charge the hybrid batteries (i.e., recovering the vehicle's kinetic energy instead of dissipating it as heat), and the "jet engine" sound is just a characteristic of this. I can't explain the precise origin of the sound - bearings, oscillation/cycling of the magnetic field, etc. - but it's how these motors sound, also under acceleration (particularly noticeable in EV mode).

#2

Building on #1, what we are feeling is not related to the service brakes. Again, what it is specifically that is causing this shudder (which, as I said, is intermittent in my car) is not clear at the moment (though under investigation in my case). However, putting aside any issues you might have had with your service brakes (yours are fine now, and mine have always been fine), this problem has nothing to do with the brakes, even though rotor warpage is a good analogy to explain what we feel. Something is happening within the motor-generator (MG2, I think) and/or within the CVT or CVT-to-gas-engine interface that creates this jerkiness. Throw the car in N, this is all disengaged, and your car is stopped strictly by the service brakes, which feel smooth as you (and I) describe.

#3

Not sure precisely what you were hearing. However, to the extent that what you heard is related to the pads floating within the caliper due to loose spring clips and/or not enough grease in back of pads (a known observation in the 460), that would be gone when the brakes engage, which you are doing by virtue of stepping on the brake pedal while in Neutral.

I hope this helps in some way. Allergies are affecting my sleep, and I don't feel particularly coherent by this time of the day

hfahmy

Very helpful! Thank you!

Is there anything I need to do about the brake shudder from the regen? Take to the dealer (CPO)? Is this considered normal in hybrids and I am being OCD?

caha14

I don't know that it is normal and, in fact, lean strongly toward it not being normal.

For one, I've never noticed this in other Lexus and Toyota hybrids, and if anything, I would expect the 600 to be smoother, not less so, than any other vehicle in the lineup. Secondly, the fact that it comes and goes, where sometimes there is zero shudder in my car, only underscores the abnormality of it. Lastly, there are folks here who claim to have no shudder.

So, while the issue (whatever it is) may not be major, I truly believe this is not normal.