hybrid450

Hello, I own Lexus GS450h from 2008, the car worked and still works fine but I need your help, because I think something bad is happening to it lately and I have no idea what it is. About a month ago, sometimes I heard a tougher engine work or some kind of knocking once the engine started while driving on the battery. It happened like 1-2 times per around 40 minutes driving. Sometimes it happened again, sometimes I never heard it for the whole ride. It had not happened before month ago at all.

Then, like one week ago, I had my CVT transmission oil flushed dynamically (whole oil was changed using a special machine that made it pump up the whole oil using the transmission's cooling system and pressure to make it safe). The car has around 225,000km mileage and it's been the first AT oil change. After the change, while I was driving, I heard that "knocking" harder engine work again for a few seconds, then for the whole road it was all fine. But...

After I parked the car for the night in the garage, I turned on the engine and I heard a very scary knocking, like in the center/under the car but not sure. It starts like 1 second AFTER the engine turns on and lasts around 10 seconds, then it becomes quiet. While driving, sometimes I hear the knocking come back, only when the engine turns on and it lasts a few seconds, but sometimes it lasts infinite until the engine switches off to battery, or if I rev up higher then the knocking also disappears or it cannot be heard. Now, sometimes that knocking is there for the whole ride (while the engine kicks in), sometimes it happens like before the AT oil flush (so from time to time during the ride), and sometimes it doesn't happen for the whole ride, but sadly it happens much more often now to knock.

What I noticed and tried:
- when the car is left for a few hours, no matter if it's cold or warm, the knocking happens the first time the engine starts up. E.g. if it starts up on battery, the knocking will appear when the engine turns on while I drive.
- when I am in "P" (Park) and the car is started up after a whole night, I can hear the knocking somewhere in the center of the car
- when I drive, the knocking is hearable more on the left front side, but it might be just that it's echo'ed differently while driving
- I recorded a few videos (links below) and tried to record one under the car on first startup, but I can only hear normal engine work without any knocking. I tried to record it beneath the hood - also cannot hear any abnormal knocking. I only caught the knocking while recording with my phone inside the cabin, near the driver's foot and the center console.
- I tried to "reset" the ECU by unplugging the battery for 10 minutes (I thought maybe the AT has to adapt to the new oil pressure or something), the first start was louder than usually due to higher revs, the knocking took much longer and was also louder. After some driving, I get a feeling that it happens more rarely when driving now, but still happens on every engine startup after night. I drove around 70km after the "reset".
- the noise is NOT metallic
- it looks like the noise is dependent on something because firstly it knocks slowly and then goes faster, sometimes it's even rattling I'd say, but it's not always connected with the engine revs being higher.

Now what I thought at first that it's the transmission, because why it suddenly appeared on cold starts after the oil was flushed? But then I realized that the knocking already was there in the past, but only when driving, so I am not sure now if it's transmission related or maybe rather engine? Driving on battery doesn't make any knocking noises either. Pushing the gas pedal while the car is in "P" and warm - no knocking (it happens on first start, if car starts on battery). The engine oil level is almost half full, the coolant level slightly above MAX (both when warm and cold, but it's been like that since coolant change and no issues back then), so I doubt they cause it. The only recent change was that AT oil change, but like I said, the knocking happened before when driving, unless it's a different knock on startup and different when driving... then I would be even more pissed.

Anyway, I really have no more ideas what it is and if it will cause any harm soon or not, but definitely it should not happen, neither during driving nor starting up after night. So I am asking for your help or advice, maybe some of you had a similar issue/symptoms.

The videos from start-up after night are below:
1. Recorded near the shift lever: 2. Recorded near driver foot on the center console side: 3. Recorded AFTER unplugging/plugging the battery after night for 10 minutes to reset ECU:
And the last video, least hearable but it is there when you tune up the volume, I drive on battery and push the gas a little more to turn on the engine and the knocking appears:

Hope someone can help.


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twincams

Is the sound very loud when u are outside the car or driving with the windows down?

hybrid450

Hey, no - the sound is more hearable inside the cabin. Me and my friend could not hear it outside when it occured, also with windows down while driving I don't hear it louder. Moreover it cannot be heard with the hood opened and my head above the engine, I only hear the engine noise.

By the way, I recorded some more videos and apparently the knocking is hearable (It's barely noticeable due to engine noise but it can be heard if you focus and tune up the volume and use headphones) under the car just under the gearbox. I tried a similar video under the engine, and I could not hear it. But on two videos I can hear the knocking in the background when the phone was lying under the gearbox. Thus, would it be possible for the knocking to be caused by gearbox only while engine is running (and not always)? Wouldn't it be all the time and even on the battery with engine off?

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twincams

Does it happen when u are accelerating, cruising, braking, or engine braking?

What is the battery state of charge when it happens?

Are u able to pay attention to the energy flow on the display, to see the coloured arrows, when it happens?

Can u try to see if u can immediately shift to neutral when the sound appears to see if it also disappears at the same time?

Maybe u can let the state of charge drop to 2 purple bars to make the engine run continuously and then drive around at very low range of speeds to see exactly when the sound appears very consistently to be get a more accurate diagnosis.

My guess is that if the sound does not follow engine rpms exactly then it is not likely to be engine-related. If it is really from the engine then the only possibility could be the Dual VVti system that relies on engine oil pressure to function properly.

The problem seems to point towards one of the 2 electric motors inside the gearbox, but it is just my wild guess.

twincams

Repeat post deleted

hybrid450

Accelerating - yes.
Cruising - seems to happen only when in manual (S) mode or when the engine kicks in for some time, but I think it starts to happen more often in D mode too even when normally driving with engine running.
Braking - didn't notice it while braking, most likely due to the engine being shut off or running on low rpms then.
Engine braking - on S mode yes, I can hear it. Best hearable on low rpm or high rpm.

It happens on any state of charge, from full to low, does not matter.

I checked the arrows, and same as above, it happens on every combination of arrows, including arrows indicating running on battery only, BUT engine was running on low rpms in the background. The knocking is gone as soon as I stop the car and the engine shuts off itself. Running again from 0 on battery (with no engine working at all), there is no knocking.

I tried that when I started the car in the morning, and then again after some driving - shifting the gears does not change anything, it knocks the same all time. I recorded that here: https://photos.app.goo.gl/rp74TBvWuyLS2fMFA (sorry for some voices from phone in the background)

I drove with the battery on 1 purple bar, so engine running all time, and it knocked like all the time, from low to higher speeds (to ~120/h you can hear it, on higher speeds you can hear that something is running much harder/louder but you cannot hear the knocking). Especially on higher speeds, when you push the gas pedal harder (like to 60%), it's very bassy and noisy, but I cannot hear the knocking then, but obviously it's not normal because it wasn't that loud before the knocking appeared.

I assume that if that would be VVTI, then it would be rather be on cold engine only (I had that rattle sound which was a dry rattling once when the car stayed outside for 2-3 days, but it did not happen again since then, most likely due to 2 oil changes and staying in garage now). The sound doesn't exactly follow the engine RPMs, but revving higher makes the sound louder, and sometimes it is also faster.

Do you think the oil change could break something there? I mean, that knocking while driving occurred a few times BEFORE the ATF change, but like I said it never happened on start and now (after ATF change) it happens every time I start the car and engine kicks in. Just not always when driving, but much more often now, almost every ride has some knocking or all road knocking.

Few more things:
- last time, there were two cases when the car stayed unused for whole day, the car started up usually with knocking, but there was not a single knock while driving the car then. Maybe it was just a coincidence, because knocking while driving does not always happen, but maybe if the car stays unused for 1 whole day then it matters?
- when driving in S mode, I found out that the engine does not get turned off in this mode. Thanks to that, I can come to a full stop and the knocking is always there - this is different in normal (D) mode, because as soon as you stop, or even drive slower, the engine might shut down and the knocking is gone then. So definitely I will try to find out somehow where the sound is coming from with the car stopped in S mode.

Video showing that with opened doors the knocking is almost not hearable (even in reality, same with windows down), and closing the doors/window make the knocking really stand out: https://photos.app.goo.gl/C4knZpyahWDTuTsz6

Video showing revving in P mode: https://photos.app.goo.gl/cemdHw6R6nEJ8oxJ6 (there's also a weird knock - stop - knock at the end when engine shuts off)

I am giving the car to the workshop this week and I hoped I could at least find some clue for them to faster identify the issue, although knocking happening in S mode on stopped car will definitely help them identify it.

twincams

From your detailed observations, it seems like a shot engine/gearbox mounting issue instead of a broken internal part. Especially so if you have observed that on 1 or 2 rare occasions there was no knocking for the full drive other than during startup/warmup.

Also during higher engine loads, the mountings are stressed more to the maximum freeplay, possibly to the point where noise and vibration will readily find their way into the cabin.

Do you happen to have the full history of service records to check if the mountings were ever changed before?

hybrid450

Well, the issue is that sometimes it's not there for whole ride, but most often it's there for the whole or 80% ride. Also, sometimes it's happening like: knocking 1s - engine running normally 3s - knocking 1s - and so on (happened today when stopped on S mode).

Would mountings cause such symptoms randomly, but more often they would be all the time?

Also during higher loads and higher speeds, it works louder/bassier only when knocking occured earlier during the ride. If no knocking, then even on higher speeds it works all normally and engine sounds great. Wouldn't mountings cause it to work louder all time?

Yes I have the full history, mountings have never been changed. In transmission, only the AT oil pump was changed by previous owner as the dealer suggested that (owner said all worked fine but he changed it).

twincams

I feel the confirmation can be clearer as the days go by when u find the noise getting more frequent and intense inside the cabin, but yet on the outside there seems to be no observable difference.

I certainly wish for you that this would be the case, considering the mountings haven't been changed despite the mileage, because then the fix would be straightforward and instantly comforting.

hybrid450

I really wish that this would be the case, too, but IMO if the mountings were bad, the sound would be there all the time and not random, or at least it would appear on every ride, but I'll tell them to check the mountings for sure.

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Lwerewolf

Just a thought, in case all else fails. Haven't seen this confirmed on a GS, and the symptoms are usually somewhat more catastrophic - you can look in the LS section, plenty of misdiagnosed "hybrid failures" were tracked down to this.

Part number on the GS is different, but it has the same function:

31290-30010 (the LS/LC500h use this part as well)

At any rate, from what I've heard so far - mountings are a possibility, as it does seem to "resonate" at certain RPMs when revving in park.

Re: transmission flush - the oil is ATF-WS spec, and is filled to spec (barely dripping out of the "check level" hole with the engine running and ATF temperature between 30 and 40 degrees), correct?

Re: transmission aux. oil pump - usually the two bearings go bad, it's a known DIY job.

Just to confirm, no error codes whatsoever?

lexeu

to mod: please remove my post

hybrid450

Were the first symptoms also a knocking sound, only with engine running? I'll check the threads, too.

I really, really hope it would be only mountings, either engine or AT, I assume that'd be the cheapest job among the other stuff.

The flush was done with ATF-WS spec, around 15L was flushed to properly clean the internals from the old fluid (was dark, but not terrible, nothing metallic in it). I haven't done the flush myself so I am not sure about that "check level" and oil dipping, but the guy has already done multiple GS450h's ATF's and never had any issues after them.

As for the AT oil pump, since it's been changed by the previous owner at the dealer (invoice from 4 years ago), I doubt that it would fail again after that short amount of time?

No errors, checked all ECUs both in health check mode and one by one to be sure, nothing popped up.

I also tried to do a "Reset Memory" thing in the "Hybrid Control" ECU to somehow reset the transmission's learn model and adapt it to the new oil pressure, but as soon as I started the reset procedure, the engine turned on for 1-2 seconds and then it failed saying that one of the conditions on the first screen is not met, I pictured that here:
https://photos.app.goo.gl/y7jEDT4SBB77NLG28
https://photos.app.goo.gl/6B8UHgq6KpSMsmUJ8
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Lwerewolf

If the auxiliary AT oil pump fails, the symptoms are very different.

Re: the reset procedure - ensure that the ATF temp is in the proper range (30 to 40deg.) and that the hybrid battery has >55% state of charge (SoC). Might also be the techstream adapter that you're using - the minivci clones are notoriously... bad. I'm using the VCX Nano, so far I haven't had problems with it - other than the not-so-great live data update rate. Mongoose pro is where it's at, I guess... at this point I'm justifying it, given how... interested I've become in Toyota/Lexus vehicles

The "reset memory" thing shouldn't affect this, the only time the transmission plays with clutches/bands is when it changes gears... of which there are two in a gs450h, and the gear change doesn't happen very often at all - in EU spec cars, >95kph when accelerating (or >115/120kph when flooring it), or <55kph when decelerating (unless you're in S-mode - I've had it not change gears until approximately <40kph in S-mode, for some reason).

Put it on a lift and have a look/feel. Mountings might be obvious.

hybrid450

I just left the car at the workshop and told them all I know + to check the mountings, to check it in S mode to replicate it on the lifter with someone listening under the car (I don't have such ability alone), so hopefully they find the cause.

I used the MiniVCI cable so yeah, could be that, but I could not find the required temperatures or SoC anywhere in the internet for this Reset Memory, so didn't check that before starting the procedure - so it could be the values were different than you provided. But if you say it has no other effect than on the "gear" change, then yeah it will not matter in my case, because the knocking is happening in both gears, of course with better audible knocking noise in the lower speeds. I have to admit, that after the failed "Reset Memory", I had a feeling that the gear switch was longer and more sensible, but it "adapted" itself after some time. Anyway I also wanted to reset the transmission memory to better adapt to my driving style, but the "Transmission learning completed" value is always "yes" in the Data, no matter if I disconnected the battery for 10 minutes or did that failed reset memory.