Lose break pressure when the truck starts

1999 GMC SIERRA
175,000 MILES
Avatar
DEVORE_80
  • MEMBER
  • 1 POST
When bleeding the brakes with the vehicle off there is great pressure and pedal. Once the truck is turned on, all pressure seems to disappear and little pedal remains.
Nov 22, 2011 at 1:30 AM
Advertisement
Avatar
RASMATAZ
  • CERTIFIED EXPERT
  • 75,992 POSTS
Check for an external leak and also the brake master cylinder
Nov 22, 2011 at 2:34 AM