2005 Toyota Prius, Grinding Noise when Accelerating after a Complete Stop

welcome!

that's pretty loud, would someone be able to hear it if they stood next to the car?

have you looked underneath and in the wheel wells for any loose underbody covers or liners?

 

I wouldn't assume your transmission is toast unless acceleration also feels bogged down while that noise is happening. The water pump replacement means belt off which is easier if the plastic trim/undercarriage piece on the inside of the right front wheel well is unpinned. If that's loose it could be dragging against the RF tire in a certain speed range.

 

there is a clutch/damper between the tranny and the engine that sometimesgets noisy and needs to be replaced. i hope that isn't it.

 

Hello! Having what I think is the same problem - have you been able to safely get around for a bit now?
Hoping to get through a few more days on it.
I noticed a little squeak which after about a week turned into this. Would love to hear any solutions and will share whatever I come across.

 

We just bought an 09 and im noticing the exact same thing. Any idea what it is?

 

I am having this EXACT same noise/issue on my 2004 on takeoff. I can mitigate the issue based on how intense I lay on the accelerator, if I punch it it causes it to prolong the noise and make it more intense. No matter the case it will smooth out and go away eventually. If I baby the accelerator I can almost dodge the noise completely. It has been driving me crazy as I have found nothing on this issue until finding this thread, mine is doing the exact same thing!

Though it was happening before I did any of the following work, the noise remains and seems to be affected by temperature or how hard the car is being driven overall for the current drive session. Car drives like normal up until certain certain temps or something occur...I am stumped.

Recently completed: typical oil change, transmission fluid (genuine Toyota WS fluid used), accessory belt replaced (tensioner pulley seems fine), replaced front struts/coils with Detroit Axle easy swaps. Car has 186k with a rebuilt HV battery going on 3 years olkd now and near no issues aside from a few bumps and bobbles up front due to bad bushings I believe.

Has anyone in this thread resolved their issue? Could a bad water pump bearing on the ICE make a noise like this? Any information on this would be amazing so I can figure out what is likely 99.9% wrong with my car as well, thank you!

 

Same exact grinding noise issue on my 14 Prius C 87k with a newly installed catalytic converter shield, which was also when I started noticing this problem. Strangely enough, OP 05prius_pal and VOXul also have catalytic converter shields. I think I'm gonna remove mine, go for a test drive and see if that fixes it. Will post an update.

 

Did you ever take on this feat of shield removal to see if that was the gremlin? I know I had my catshield installed for about 5-6 months before this issue showed up so maybe it is something odd where the metal plate expanded/contracted over time to start a rattle under there. I believe mine is riveted on my frame so removal for me isn't exactly easy or temporary, haha.

 

Did anyone on this thread figure out the cause of this noise. I had the exact same thing happen to me earlier today. It got worse as I drove, and by the time I got home, I was worried I was doing real damage. Also had the BRAKE, (!), ABS, and VSC lights turn on within a block of home. Have people been driving with this issue for any extended period of time?

 

The noise in the OP's video, to my ears, is surely something contacting the exhaust pipe.

There are some stamped metal heat shields above the exhaust pipe to protect the body floor, and in an old-enough car any of those could come loose and hang down, and vibrate against the pipe and sound awful. Happened to me on a road trip this spring. I pulled over for the night wondering if the car was toast.

The next morning I got down and reached under and felt along the exhaust pipe (careful if you've been driving, hot!) and found a heat shield that was hanging down above it, and when I gave that a twang with my hand it made the same awful rattle I had heard the night before, so I realized it was nothing serious and continued the trip. I keep a little roll of stainless steel wire in back, so I stopped at a Jiffy Lube and asked the guy if I could drive over the pit and just tie that shield back up away from the pipe. Stayed quiet the rest of the trip.

Another possibility, mentioned in #11, is the exhaust pipe contacting a cat converter shield. Maybe you have one of those? When accelerating from a stop, the torque on the driveshafts tends to twist the engine/transaxle so the exhaust pipe moves downward, so there could normally seem to be enough clearance between the cat and the shield below it, but under acceleration the cat moves downward and rattles on the shield.

If that's the problem, I'd recommend doing something about it before too long. A floppy heat shield is one thing, makes an annoying noise but isn't going to hurt anything. But a securely-mounted cat shield, on the other hand, could put some force on the exhaust when you accelerate and the exhaust gets pushed down on it.

I had an old Bronco II once where a tranny shop managed to reinstall, backwards, the skid plate that went under the transfer case. That skid plate was shaped to give the exhaust room to move, but not when the plate was backwards. I didn't figure out that was what they had done until after some months of driving that way, when my catalytic converter broke off from the repeated flexing force.

Nothing making a rattle-on-the-exhaust-pipe noise is going to be the reason your brake system lights are on. You should just go ahead and find out why those are on. If you haven't got a scan tool to use for that, you can do it this way: Blink (a/k/a Flash) Codes – How to. | PriusChat

 

Brake system (BRAKE, (!), ABS, and VSC) errors are serious!
Check the error codes to find out exactly where the damage is or the unit responsible for issuing the error code.
One of the brake cylinders on the wheel rims may be damaged.

 

So I'm relieved to say the answer is what I suspected. The exhaust pipe/cat was leaning against my cat shield which caused a terrible grinding/scraping/banging noise just like the one in the video the OP posted. The culprit was one of the rubber bushings on the exhaust pipe hanger (the bushings fasten the hanger to the body of the car), which had torn, and so wasn't properly doing its job of holding the pipe up, leading to the pipe vibrating against the cat shield. See attached bushing pic for reference, ignore the blue recycling bin underneath. The bushing in the pic is fine, the torn one had a rip through one side of the outside oval.

 

This gives me hope it is something simple as you state! I did have a shield installed after my CAT was stolen a couple years ago and my noise showed up about 6-8 months after the shield install. Through my manic self sleuthing and trying to find clues to this noise I have run across people with damper plate issues between the ICE and MG1 where plastic retianing clips break and the balance springs shatter inside the case. You wouldn't think this could be something that severe? I figure if that damper plate was not balancing the ICE and MG1 properly the noise would happen every time those systems engage on takeoff, right? My noise definitely seems to be influenced by temperatures which made me think maybe the ICE mechanical water pump or something. I cruise the highway home everyday to and from work, I can guarantee the noise strikes my car on that first red light takeoff from the off ramp but by the time I hit the last light before my house (about 5 miles away from highway) the noise is almost completely gone on all takeoffs so it could very well be a shield or that catalytic downpipe striking the shield moreso due to the system being very hot and fully expanded?

 

Was the noise on your vehicle temperamental, not happening all the time but seeming to happen stronger/louder if the system was really hot?