Probably your power brake booster has a air leak, and is letting off pressure.
coz ur momma is in ur bonnet!
Just under the left side of the dash!
under the dash, driver side
it is located under the steering wheel column. unscrew the cover under the dash and it should be there. that's where it is on my Volvo s80
underneath the dash (under the steering wheel)there is a switch you have to pull...
under the dash on the passengers side and below the glove-box..attached to the firewall
Hello you need to change your master cylinder.
Perhaps a vacuum leak either under hood or under dash Perhaps vacuum booster unit check valve defective
you have a control vacuum leak, listen for hissing noise under dash when engine is running.
Under Dash Passenger side to the right of the kick panel
Sounds like a vacuum leak - check the hoses to the vacuum actuated motors under dash Could be a bad check valve in the vacuum booster (for brakes)
Under the dash above the radio remove the plastic panel this is a common place for the CB check under there.