Sounds like clicking noise from the engine

I trust you've checked your oil level?

Failing that, is the a/c on - is it the a/c relay?

Trust there are no nails in your tyres.

Is a twig or small branch stuck under the car

Is the plastic under tray (under the car) come loose if you've driven through a flood or large puddle? If they come loose they can flap about at 50 mph.

Anyone else any ideas?

 

How far a part is the clicking, is it once a second, fifty times?

 

A leaf stuck in the a/c fan? Brake pump? Front passenger side seat belt tapping against the plastic side panel?

 

It sound like an injector going bad, dealer should see it on a scope.

 

I'm glad you brought this up. I just developed a similar (maybe the same) noise over the past two/three weeks. Mine is between 20 - 30 mph when I leave the house in the morning and go up a slight grade. Sounds like a loose bolt in the engine area that is vibrating. I'm trying to capture it on my phone and will post if and when I'm able too. I did have the TSB for the engine knocking done not too long ago and I'm wondering if there is a bolt that worked a little loose?

 

Sounds like you answered your own question.

Or is this a sound applicable only to those with new replacement manifolds?

 

Good question. I would be interested to hear if the OP had the TSB / manifold replaced.

 

That is the standard line. I would ask to have the shop foreman take a drive with you. If that does not work, find the Toyota Customer Representative at the dealership. Yes... there is such a thing. Made a big difference in getting my issues dealt with!

 

Here is a short video that captures the rattle noise I hear coming from my engine area (hope you can hear it). Not sure if this is the same noise the OP was hearing or not? Mine is at about ~25 seconds into the video. Going 20 -30 mph up a slight grade. Seems to only happen when engine is cold (no warm up) and going up a slight grade. Happens nearly every morning on my way to work.
[ame=http://www.youtube.com/watch?v=PX-19btKSdw&list=UUtDg-YepVr_pQDcc6qnUCFA&index=1&feature=plcp]2011 Prius Unknown Rattle Noise - YouTube[/ame]

 

I have experienced this when I drove a rental Prius and my own Prius. I would think it is normal, but I really did checked my trunk because I thought it was from my trunk. Conclusion, we have good ears.

 

Mechanic told me the clicking sound is an indication that the 12V battery about to go. You might want to get that checked.

 

I'm getting the same clicking noises too, when the engine is cold and upon slow acceleration. The noise goes away soon after the engine warms up.

I have not had the engine knock TSB done so everything is factory installed. My guess is either valve train rattle or piston slap (similar to Chevy Tahoes)?

I'm going to wait and see if it gets worse before I go to the dealer.

 

Interesting... never heard this in my car. Had both T-SBs done related to the engine just recently but never heard this prior to that.

 

Which oil do they use in Alaska? Is it 5w30 like in Canada?

Maybe the thinner 0w20 oil can cause this? I remember my car ran quieter when 5w30 was used by mistake one time.

 

0W-20 GC... just like the rest of the states. That is probably better up here anyway with the colder temps.

Just from listening to the video, it should like the noise if coming from the inside of at the most up against the firewall. Could also be the hood prop...

 

I'm going in Saturday morning for my 15k maintenance. I mentioned it to the service department in the notes when I scheduled the appointment online. I have the video and I'll see what they say the noise is. I should have an update tomorrow.