I need help with my 1997 Ford f250 the brake pedal slips and does not brake well I make a second attempt to brake and it slides to the ground and I changed the vacuum pump the booster the master cylinder the RAP valve and it remains the same
You apparently have a gas engine (diesels do not have vacuum-operated brake boosters), so my guessing: 1. Run the engine for a couple of minutes, then turn off. Push the pedal down several times slowly. If after 3 or 4 times it comes back up, you do not have an air leak in the booster. Start the engine, push the pedal down, shut the truck off. If the pedal stays down, it's okay. Then perhaps the plunger for the brake booster needs adjustment. Or, 2. Bleed the brakes again.