Why does my ford focus stop running when I hit the brakes

when you brake ,maybe the engine moves due to broken motor mounts, that can cause problems with or on your hoses , like .
inlet hose,vacum hose, crank case hose, and pcv hose. most like it the last one.

This could be one of two things. The test that you need to do to see what it is: Before you stop, shift to neutral and see if it stalls. If it does not stall then it is a transmission problem. The transmission is not letting go of the engine. This is most likely from a torque converter problem or a sift valve. If it does stall then it could be something related to a vacuum leak in the brake booster or a short in the cruise control.

check your brake buster

Did you change the turn signal switch?

on the top back side of brake pedal there is a brake light switch. it maybe just sticking or its out of adjustment. the brake pedal arm hits this switch everytime brakes are applied to activate the stop lights. have a good day !! if it just sticks you may be able to free it up.

Clint, you might want to check your break switch to see if your button is stuck. It is right above your brake pedal. The pedal led actually hits the button of the switch. See if you can loosen it.

Whens the last time you had them changed. Probably hitting the wear indicators. Need to have them serviced.

if you are trying to save the rotors,put a block of wood against the rotor and hit it a few times hard on the top then to the bottom,then the sides providing that it doesnt turn around.if you hit the center be very careful not to hit the lug bolts,it sometimes helps to put 2 lugnuts back on to help protect the stud.

The Focus was desinged in Europe,Think German.......Vw has a similar issue.The brake light switch goes bad.......no lights no shifting out of park.

it's not dangerous to the point you will not be able to stop how ever the longer you wait to replace the pads the more damage it will cause to the rotor which will cost more to replace. the sonner you replace the pads the less expensive it will be.