I have a 2014 Prius (4 or 5). I have 216,000+ miles on it and have never replaced the main battery. Recently I started noticing an intermittent rattling when I first accelerate, not always, but intermittently. I had purchased tires for it in December, so I took it back and they rebalanced the tires and said that the were unbalanced. I then took it into the dealer as I also needed an oil change/inspection and had them do a realignment. Hoping the problem was solved I drove it around awhile. I did notice the issue a few times (3-4) over the next couple of days. Finally after a long wait in a drive through it started happening while idling and I noticed the main battery indicator was low, so it might have started at the same time the engine kicks in during a long idle. Can this be an early indication of my main battery going bad?
Check if the middle exhaust heat shield is loose. The shields have a natural frequency which is the same as the ICE at low revs so the rattle sounds like its coming from the engine when it is just a loose shield.
Rattles suck. Can be difficult to find as one may think the rattle is at the front and actually the rattle is in the rear. My 02 cent comment. When idling is the engine "smooth"? Lift the car, make the car idle and crawl under the vehicle.. Take a rubber mallet with you to test panels if the rattle is not apparent. Heatshields, fender liners would be my first areas to inspect as mentioned above. With 200K mileage, perhaps some suspension component or motor mounts needs attention. Checking bolt torque can also help find something loose. And going to difficulty/ false leads, do forget to check the glove box for an item rattling. At this time, you mention after long idle, so some engine component may be on it way to failure, but that is a wild guess, again at this time. Good luck.
That's why you haven't had a problem..... I arrived at Church late Sunday and didn't have anywhere to park except in the front of the building where everybody could see my v. After the services three different people asked me if my head gasket had blown yet. They were all previous prius owners with over 150,000 miles.
And my Head Gasket did blow................. fixed it my self.... this is the only vehicle I've had that blew a head gasket..... and I'm 65. Problems I've had Traction Battery Invertor Water Pump Brake Pump and Master Cylinder Noisy Trani
Never personally had a head gasket blow, but had a car returned to me with one blown. Person I lent it to for a week ran it into the red on the Temp gauge and it warped the aluminum head.
