vibrating while at red light coming from brake pedal

So my brakes were pulsating so I had them changed today. I drove it around a bit and after about 60 miles I noticed when I was COMPLETELY stopped at a red light I could hear this vibrating noise sounding like its coming from my brakes. I can hear it when i stick my head out the window and from the inside of the car near the floor. the car is an 07 ion with just barely 50,000 on it. I'm pretty sure its brake related but not sure what they did to it. something must be loose. it doenst do it when its in park only when I have pressure applied to the brake pedal. the second I let go it stops.


Any ideas?

Sheryl

I would guess that you have a vacuum leak. The power for the power brakes comes from the vacuum system. When you apply the brakes the vacuum leak is probably causing a misfire to be more noticeable due to the load. Does your car have a tachometer and if so, does the engine speed drop when you apply the brakes?

-Rod

i'll double check today on my way to work but i didnt notice it drop no. and when i first apply the brakes it is fine but if i lift on the brakes and reapply pressure it starts to vibrate so the vaccuum leak could be possible. i just though it was so ironic it started 60 miles after my brake pads and rotors were done. figures right haha

thanks