2010 Rattling in engine bay on start up?

The only thing I advise is to try to do more research or take it to the dealer...hopefully yours is still under warranty, thats how mines was fixed.

 

Old thread I know, but my work 2014 Prius v (lowercase v for the Prius v wagon because only 2010 Prius used uppercase Roman numerals for model designation) with 46k on it has begun doing this when parked overnight in 50F California "cold". Lasts only 5 seconds or so, but sounds almost like a broken belt end flapping around in circles, the whole car shakes and shudders, giving it gas clears it instantly.

Paul

 

Welcome to the strange world of phenomena that Toyota does not admit to happening.

You had a startup misfire. Probably from condensation in the intake manifold. It would interesting to know what you did with the vehicle the last time you drove it, before the event happened. My reading indicates it happens after a brief (seconds) start time in a high humidity situation. Then hours or days later, when the engine is started again, it misfires and shakes like something is about to fly apart.

Except it doesn't. The rattle stops in 10-20 sec and all is well.....

For 201o and 11 vehicles there might be a TSB that says loud engine noise is due to a bad motor mount. IMHO, the two issues are unrelated. The startup misfire is a misfire, clearly a cylinder not fireing (in my 2011, there were cylinder #1 codes). The motor mount issue, while real and worse with cold, seems different.

I have a 2014 and 2011 Prius. I have driven them both, one with 7k miles, then other with 41k miles, in identical temp and atmospheric conditions. The 2011 clearly makes a LOT more noise, especially when cold. But its not the start-up misfire. What is the problem with them 2011 is yet to be diagnosed. Might be the motor mount. It did the misfire rattle only once....

 

I have a 2011 with now about 75k on it. This has happened to me 3 times. Each when it sat overnight when Temps were 50 to 70 degrees. Once in Florida, Kansas, and upperstate NY. It rattles like something is loose under the hod but only for 5 sec. After that I turn it off fast then on again then it stops. Then nothing again for weeks. I wish someone knee what it was and a way to fix it.

 

Got an extended warranty for the knocking issue and EGR valve in the mail. 150K

 

I have a 2015 Prius that has done the same thing twice on early-morning startups I have less than 25000 miles on the vehicle and it did it in the first 10,000 miles has not done it since

 

"rough idle and/or rattle noise from the transaxle at cold start due to a sticking Exhaust Gas Recirculation (EGR) Valve" is supposedly covered under a Warranty Enhancement Program, but not really--because the dealer can't recreate it (tends to happen on cold mornings after it's been parked for a while). I showed them this video of mine doing it:

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Not good enough for the dealer--or the Toyota Customer Assistance Center. To recreate the condition, it has to be cold and the vehicle has to be parked for a while. So to make sure your dealer can see it misbehave, you must a) identify a cold night at least a week in advance, and b) then leave your car at the dealership for that week. Ugh.

 

15,500+ views and here's the fix.

You sir need an occ, Oil catch can. I bet the rattle goes away in about 30sec. Toyota has no fix for this. If you continue to start your car with this knocking, you will end up blowing a head gasket. Remove your intake tube and air filter right above your throttle body. When you open up the throttle body, you will see oil inside the intake plenum. That oil/water/fuel is what is causing the knock. The occ catches a large majority of this and stops the knock. You will see more knocking during colder weather than in warm.

 

Toyota has no fix for this, Have you looked in the garage to see who is working on your car. If there is no code they cannot fix it. There is no talent in mechanics any more. They need a code and the computer to tell them what's wrong with the car. I was lucky enough to learn how to fix cars with both computer and manual diagnostics. If you are still under warranty, you do not have enough miles on your car yet. Brand new cars that are clean run fine. The cars with some miles on them are the problem. Toyota has a poorly designed pcv system that blows too much oil/water/fuel into the intake plenum starting knock.

 

What was the problem

 

Loud banging at start-up, coupled with dropping coolant level, points to head gasket failure