Grating Sound when Gas Engine is used, help!

TL DR: the black plastic shield under the front bumper and front passenger side fell off while driving and I ran over it. A few weeks later the car makes a grinding noise that turns into a grating noise whenever the gas engine is engaged. Is it safe to drive it to the mechanic? What could be wrong?

Background info: I have a 2011 Prius hatchback (regular trim) with 179k miles on it. Bought it used at 171k in March 2020. Then we WFH’d so I didn’t drive it much. I had the engine oil changed twice according to schedule, replaced the 12V battery, and replaced the strut assembly, PCV part and a leaking bearing on the driver’s side. Dealer diagnosis came out clean.

On 7/10/2021 I was going 50 mph on a freeway when the black plastic shield (splash guard?) that is under the front passenger side began dragging on the ground. I pulled over, saw the piece hanging and taped it up to the bumper. It was just the passenger side, cracked. It held and I went on my way. I usually drive in the city, so max 25mph and usually slower because of traffic. When I do go on the freeway I usually go 45mph-55mph. The tape would sometimes come off but the plastic didn’t drag again. I noticed at higher speeds it was more likely to fall and drag.

On 8/3/2021, I was driving on the highway going 55mph when I heard a loud ripping crunch and bumpiness as I drove over it. I saw a huge L shaped piece of black plastic piece in my back mirror and couldn’t stop to pick it up. When I got home I saw the dangly piece I had taped up had fallen out (probably because of the wind/speed) and I ran over it. I heard the loud noise in the center of the car as I ran over and was worried I knocked anything out of its place, but there was no noise, no lights on the dash.

Suddenly on 8/9/2023, as I started the car and pulled out of my parking spot I heard a grinding/squeak from my tire axles and later the car just started sputtering. As I pressed the gas pedal the sputtering turned into a grating noise. I thought either a rock got in there and was continuously hitting something.

When i drive using the big battery or coast (no gas pedal) there is absolutely no noise. The tire axles never made another squeak. Its only when the gas engine is engaged (whether the car is in Park mode or running) that I hear the noise. At first it reminded me of priuses with their cats stolen. It was super loud.

What do you think is the issue? I have to take it to the mechanic but I’m afraid driving over there will damage the car even more, as its a 30 minute drive. Also, sometimes the sound disappears. When i turned the AC on there was no grinding. But later when I tried the same trick it didn’t work. So it really comes and goes, but is just too loud for me to ignore. Should I have it towed?

attaching pics and a video.

 

Also I forgot to add, what is the black plastic shield piece called? I wanted to look it up to order online. Ah im trying to upload the video but it wont let me use a link…

 

Here is the video with sound while the car is parked.

 

And here is a later video. In the beginning there is no noise as its running on EV but at 0:08 you can hear the rumbling start. Windows are up and it is very loud. Please excuse our conversation as this is from my dash cam lol.

 

How could you tell its the head gasket? From the sound? The coolant is not low, but I am taking it in to the dealer today. Thanks for reply!

 

Hey everyone thanks for your input. I took it to the toyota dealership 10 days ago and they're releasing the car to me today citing that they couldn't recreate the noise for the 2nd time (meaning initially they heard it). This is so frustrating not being able to move forward with a repair.

 

Understood, and thank you for the advice/information. To everyone who replied - this has been so helpful as I've been getting nowhere IRL. I've relayed this thread and info to my usual mechanic as well as the dealer's master mechanic, but I guess hearing it from a young female's mouth about 'internet information' won't ever be taken seriously. I'm gonna have to shop for a new mechanic, and/or consider the car a loss to tinker around with rather than drive. If anyone knows anybody (or even hobbyist) in NYC/NJ, feel free to let me know!

And once I do get an answer/diagnosis I'll update the thread for posterity!