hello, louder than normal droning when accelerating. No issue with speed, and no lights come on in my 07 prius with 180k on it. Ideas? Was hoping to go on a 1000 mile road trip next week and this happened..
If it changes pitch with the engine speed (which can stay the same as the vehicle accelerates due to the CVT-like-drivetrain), I agree, it's mostly likely your exhaust, this is where I would look. Pretty easy to jack up the car and then examine the exhaust system using a flashlight to see if there are holes. If the droning changes speed with the vehicle speed but not the engine speed, most likely cause is wheel bearings. Less likely is a bad motor mount. I've had a car where you could hear and feel the vibrations of the engine on acceleration when the motor mount failed (metal-on-metal inside the motor mount). This you can tell because it happens more at the start of accelerating, and especially when accelerating rapidly from a stop due to more g forces on the engine. The sound goes away or diminishes a fair amount as the vehicle picks up speed.
