2010 Knocking and Thunking on Idle - with video/audio

I don't see anything lit up on your dash I don't even know if I'm seeing any of your dash I don't know what this video I do see the battery no the econo mode and all that but are there lights on on the dash the red triangle any amber lights I don't care about the TPMS or tire pressure light the other lights check engine red or amber triangle any of that going on You're in the area of head gasket failure for this model and this kind of mileage but this is a stretch at this point because that noise sounds pretty consistent almost like the air conditioning compressor or something for it to be making a noise like that it doesn't sound like a piston skirt has cracked or falling away into the pan but it's possible a lot of possibilities they're going to have the car live so they'll be able to put a stethoscope on it and check things really read codes and all that here we would just be speculating wildly speculating probably

 

The sound in the video sounds "slightly" off, a very fast-paced buzz with a bit of modulation. The more typical cold-start shake is very alarming, slower/harsher. That said:

Has the EGR (Exhaust Gas Recirculation) system ever been cleaned (including the EGR passages on intake)? This is best done by 100K at the lastest. Carbon inexorably builds up in the system, thwarting it's design purpose, which is to reduce emissions AND temper combustion chamber temperature.

My 2 cents: neglecting to do this will lead to head gasket failure. 150~200K miles is the danger zone. Usually at the adjoining wall between cylinders one and two.

There are a few places in the states that'll do it effectively and for reasonable price. Tampa Hybrids in Florida, and Hybrid Pit in California are two I've heard of here. Both charge around $600~700 IIRC. Other'n that: DIY is typically the way to do this.

Dealerships are typically the LAST place to consider: they will not clean things, only replace. That is usually completely unecessary, and entails around a grand worth of new parts. Plus multi-hour labour rates.

More info in first of my signature. If you're on a phone turn it to landscape orientation (horizontal) to see sig's.

 

I did it on my 2009 model, not an easy task. Hardest part to get out is the egr cooler, and especially the lower bolt. Its deep under it. It took at least 3 hours. I just replaced it. New oem costs about 200. Also clean the intake manifold, replace pcv valve and clean carburetor while you´re at it.

 

What is it doing when you have this noise? Is it shaking the engine? Does it sound like metal to metal? Does it go away pretty quick and run good the rest of the day?

 

Likely a head gasket caused misfire.

 

The lower nut (screws onto stud) can be removed any time. I would do that in advance, and leave it off. Backing out the stud can be done too, and again, left off. The latter requires E8 socket, and with cramped quarters, a lot of patience and care.

This trumps all the EGR cleaning, needs to be diagnosed first.

 

Is it a Toyota dealer or an independent Prius experienced shop? If it is not one or the other, mechanics are often confused.

 

if they can't pinpoint it, i would clean the egr circuit and see how it behaves.

most dealerships don't understand the egr problem, because toyota refuses to fess up in a technical bulletin.

your mech should certainly know how to test for a bad head gasket

 

The only effective test of an early stage head gasket is a borescope inspection after pressurizing the coolant for a period of time. Requires a high quality borescope capable of seeing the head gasket in the cylinder while looking for very slow drops of coolant. Traditional coolant combustion gas detectors, compression or leakdown testing will leave them dazed and confused. Otherwise you drive it until it gets worse, risking a bent connecting rod.

The egr can't fix the problem. It is extremely questionable if a clean egr can prevent it. Has not worked pre or post symptoms for many. It is a good thing to do during a hg job or as a feel good activity.