I wonder if this issue you are talking about might be an injector sticking? I've seen quite a few Prius that sound like they have a bad rod knock (it's actually the transmission making the noise). Some of them sound so bad you would swear the engine was toast (see video) but in the end a new injector was actually all that was needed. Depending on how badly the injector was clogged it may make more or less noise. Something to look at anyway and injector problems are more likely on hybrid cars since they go through continual on/off cycles which causes deposits to form much faster than with normally driven vehicles.

 

Same noise in mine, '06 Hibyrd HiLand 265k
It all went away after I filled the transmission up.
It was 1 1/2 qts low. Too easy! Holds 4qts ttl.
nice & quite now 🙂

 

...

 

I know this is an old thread but I'm hoping someone has an answer. I have an 08 highlander hybrid with EXACTLY the same symptoms as you described. I can feel the knocking through the driver side axle. The transmission fluid was changed 20k ago. Took a sample and it looks decent. What can this knocking be from??

 

Hi Abbas, were you able to learn what the cause of knocking was? I have 2006 HiHy and just recently experienced this after (long story short lol) an incident I caused which triggered a dtc triangle of death warning to signal and my car sounded awful during these couple minutes! But now, just this morning I noticed a similar noise at beginning of video but doesn’t get as bad as Prius in vid.

In July I had my cvt fluid and inverter coolant changed and timing belt replaced at dealership.

I have just over 114K miles on mine and never any dtc’s prior to the one I recently caused! I’m not sure if they’re related or coincidence but the timing is uncanny.

I’m not sure if you would be familiar with my comparison but the sound mine made this morning sounds like an older water heater in an area with very ‘hard’ water (high mineral content builds up inside over time and causes similar sounding noises while water is being heated). I know the inverter pump is also on the driver’s side of vehicle in this location and that’s where it sounded like it was coming from. I had just started my vehicle and it was idling for a couple minutes and the ICE was on. I guess it could be injector like they mentioned above because I think the noise stopped or at least subsided when the ICE stopped. I don’t have a stethoscope and it was kinda hard to pinpoint location exactly over the noise of my ICE.

 

Any one looking for answers to this knocking type noise, it's (mostly normal at start up) but can also be worsened by any misfire.
the felxplate/flywheel design is 2-peice and needs a perfectly smooth engine, or it can knock and rattle. Hence why it may be heard on start-up, it takes a second or 2 for the engine to smooth out.

 

Thank you for this information @Altezzars430! It’s very helpful

Mine has actually been better for some time now so maybe the maintenance I had done needed time to ‘settle’ or something (for lack of better term) lol