Q: Rumbling noise and brake light

The brake light is there to let you know when the brake fluid is low. It is very common for it to turn on and off when it is right at the point of being to low. When you stop, the fluid in the reservoir and the force created by decelerating your car pushes the fluid forward making your fluid level just low enough to turn on the light. Once our stopped, the fluid rests back to its norm and the light goes off. This can happen under many different circumstances. If the fluid were not moving through the lines as it is suppose to, you would notice very uneven braking. Your car would move around a lot under braking.

As for the noise under the hood, I would need more detail to give you any advice. There are hundreds of possible noises that can occur under the hood. Including belts, mounts, and other types of noises coming from the engine.

If you need further help diagnosing this, I would recommend having an expert inspect the Brake Warning Light and the rumbling noise firsthand to get precise advise on what should be repaired.