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Discussion Starter #1
Hi All
I purchased a used 2016 highlander last weekend and over the week and a half I noticed that during idle and acceleration the v6 motor is producing very high levels of loud bass muffler sputter.. the dull loud kind with a "brrr". There isnt a metallic sound so it isn't the exhaust heat covers or anything.
I had my indie mechanic take a look with hoist and he couldnt tell anything on it running on idle...ie anything on the muffler. But I feel its distractingly and annoyingly loud inside the cabin with windows closed. There is no way that's normal. There are no lights on, and the car has a clean history on its 45k miles. Runs fine. Mileage is about 26mpg (9L/100).

Electric motor is whining a bit as well all the time which is also a significant but secondary concern I want to get to after the v6 engine and exhaust loudness.

Hoping someone can direct me to diagnosing both issues please.

Thx.
 

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Discussion Starter #3
As of motor... check invertor coolant level. That coolant is cooling down MGs. Just in case.
Thx. Had Toyota check it out and did an early pilot change as well (oakville ontario).
They called everything sounding as normal.
While I am getting used to the whine...though no comfortable with it...the rumble from engine at mid range rpms is really bothersome. I had a couple of folks look at it and visually the exhaust system doesnt seem out of place. It's just not outside I actually feel the rumbling inside with the windows up. What are my options to diagnose... other than compare with another hybrid and same MY and mileage.
 

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This:


compare with another hybrid and same MY and mileage.


As I do not recall any rumbling etc in my HiHy.
About the only thing I can think of causing this, as what you describe is power train vibration felt in the body, is bad torque mount on the R hand lower side. It's right behind the R front wheel, you can see it with slight attention. Elbow depth in. Toyota also has vibration dampeners all over everywhere, some might be missing. They look like rubber pegs or squares or rectangles on metal "legs", attached to various components. My torque mount was bad at about 80K miles.
 

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Discussion Starter #5
Still trying to find figure out a similar vehicle to compare it with. the burbling sound is only coming out of the tailpipe. No other source of the sound.
Was out on a family trip this past weekend - mileage is reasonable. No CELs.
Sound varies based on RPM. Particularly rumbling when accelerating uphill on a load - and when it comes on while starting in Park and/or charging the battery when sitting. I haven't tested it on Neutral if that makes a diff.
When momentum is driving the car and the load isn't that much I feel the burbling isn't that loud. Re the note on worn-out/broken-mounts... scary to consider/appreciate the hint... but there aren't that significant amount of vibrations felt inside the body - just enough audible burbling from the exhaust tailpipe are audible enough that they leak into the car with windows closed, particularly when there's no stereo going. The electric whine I am mostly accustomed by now - I kind of enjoy that.
The brrrr-ing not so much. I'll likely make a video and post here in the coming days.
Since the last few posts, I've had the exhaust examined at a couple of place. No issues detected.
And given that its happening when the car is in Park - And at specific rpms makes me think its something on the other end of the exhaust system (i.e. the engine). But without CELs no one suspects any intrinsic issues with Cat or the muffler.
 

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Your ICE should not even be running when in P.

Otherwise, as tailpipe is connected to cat and J pipe and all that to popwer train - look at the head of the snake for vibration cause. Can be as simple as lost vibration dampener, as Toyota has them all over everywhere, torque mount included. Some are on exhaust. Without knowing exact layout of them, though, it will be hard to find missing one.
Again, in P, engine should not run at all.
 

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Discussion Starter #7
Had a few more places check it out. Everyone has found the burbling noise normal. I feel is some sort of a resonating vibration thats louder when pulling load on ice only mode on hwy speed. Otherwise at lower rpms when its been inspected at everyone has given it a pass. Torque mounts, muffler and elsewhere, all seemed ok to them.

And enough time has passed now for me to just get used to it.

The electric motor whine in feed and regen mode are also something that Ive become used to.

Another 10-20k miles and we will likely know if it gets worse.
 

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Discussion Starter #8
No update on the resolution of the vibrations... tried to drown it out over the summer/fall with radio. But spent the entire winter so far frustrated. It's the most bothersome part about getting in this car and going anywhere. Over last few months, have had more exhaust specialists take a look. Had a new muffler installed, and transmission fluid changed. At close to a 100K kms. So those things helped 0%.
Because of the cold here the vibrations on the start off from stop going along with with the vibrations are enough now to be felt on the steering wheel and the gas pedal. And some stuff on the cluster and the centre console are rattling at those low rpms under load.
I still haven't test driven another highlander around same age/same mileage because there is no way this can be normal. Nothing from few dealers that have tried to diagnose. No codes. Getting close to losing my mind over this.
 

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Apparently I changed the tail pipe "rear muffler" which isn't the main muffler at all. Maybe something most people know already. But to me, Toyota parts site seems to tell that that's really the muffler.
However this is the real muffler apparently but it is all in once piece without any joints on the ONE part. A Cat, Resonator, Main muffler all in one part. 174200P372.

What I am referring to in the diagram (17420 main muffler). What I tried replacing was 17430 instead - rear muffler/resonator - too small to really solely suppress sounds.

There are other parts that show up when I search for 174200P372 but I have to click on "more images" to determine the right set up matching my vehicle's exhaust components. Other exhaust flows for same year have these individual components split up with joints but for some reason the HiHy from 14-* has this entire thing in ONE piece priced new around 2K USD!


I had another shop take a peek at it and they recognized that this could really be the main muffler underperforming due to some water build up over time inside that's damaged/rusted out the interior. I've noticed (and read here) that the hybrids produce more water than non-hy as part of the emissions process. Looks like no one else has had this issue from what I can tell since I started this thread. My next course of action is to find a used part maybe off a salvaged vehicle to either replace the entire part or worse cut out and implant the muffler only.
 

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In today's vehicles, the exhaust system is mainly made from a stainless steel alloy containing chromium. It is unusual for the system to have rust failures unless there is some normal, non stainless steel, touching the stainless portions. Most modern vehicles end up never having to replace any part of the exhaust system except flex-pipes and they're usually not that expensive. It would surprise me if your main muffler had failed - but anything's possible I suppose.
 
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