Brief rattle/knock at cold start

How many miles on it, new purchase? I would think oil would have been at full mark when delivered to you; was it higher before?

 

No rattle here, at 10000mi // 17000 since June 2016

 

Mine had the same rattle at cold startup with genuine Toyota oil but not with Mobil 1. Mobil kept it quiet for about 6500 miles, then the rattle started again. I changed the oil at 7k, again with Mobil 1, and all is quiet again.
See this thread,
Only Mobil 1 For My Prius | PriusChat

 

Can you upload a video so I can listen to see if I great something similar?

 

I can often hear mine start first time in the morning, I wouldn't call it a rattle though - just slightly more noise than if it's hot. Much less noise than say a "normal" starter motor. Or my previous diesels starting.

 

congrats and welcome!
just sounds like a normal toyota engine anomaly. 'snafu'. enjoy the mpg's!

 

I see. Yea I've always wondered about the pronounced noise and vibrations the engine makes during the first two cold turns. But like Alanclarkeau mentions, it's probably the lack of starter sounds that drowns out everything I'm not used to. I'm thinking as long as it pumps in oil before combustion, I'm at ease.

 

2019 with 5k same issue. Did you ever figure out the reason?

 

That's noisier than mine - though to be honest, I've never listened from outside. Maybe check with your dealer.

 

Does it have 0w20 oil in it, thicker at cold oil such as 5w20 will not circulate as quick.

 

My 2017 Prius has a rattle noise at start-up coming from the timing chain cover. Does anyone have an idea what is causing this noise? Is there a tensioner I can replace from the outside?

 

I occasionally have the same rattle on start-up on my 2017 as well and it's been like that since new , now at 35km and I'd think it's a normal characteristic of this engine.

 

Thank you Yousef for your response. It sounds like a metal to metal clatter with no oil lubrication for a second and then goes away. It only happens when the engine sits for a while. Do you have the same experience?

 

Yes usually when the engine is cold as I notice it more during the winter months.

 

Did anyone ever get a definite answer/solution on this? I have 2021 awd, 3,000 miles, so it still has oil from factory. When gas engine first starts, occasionally i hear this brief rattle/clicking noise from engine compartment for about 1-2 seconds (if you were not paying attention or had radio up you probably wouldn’t notice it). A little disconcerting……

 

Just think - if you had, say a Corolla NON-HYBRID, and turned the key - you'd hear the whine of the starter motor and the ICE starting up - and wouldn't notice that momentary rattle/clicking for the racket from the starter.

I occasionally hear it, but it doesn't worry me.

 

Just think - if you had, say a Corolla NON-HYBRID, and turned the key - you'd hear the whine of the starter motor and the ICE starting up - and wouldn't notice that momentary rattle/clicking for the racket from the starter.

I occasionally hear it, but it doesn't worry me.