Ok my boyfriend says that when his truck is on the pedal goes straight to the floor, doesnt stop. When its off the brake pedal has pressure again. He got some kinda cap and bled the brakes but he still has brake fluids. Hes getting real frustrated. any ideas on what to check next?
Check for leaks in the brake lines. Check the brakes to make sure th fluid isn't leaking there. If still the same, have the lines changed.
It's most likely the master cylinder. My truck did the same thing and I replaced it and it worked perfectly. It could also be the brake booster depending on what kind of truck it is. Tell him to check the vacuum line going to the booster. It is the big metal pod that the master cylinder bolts to. If that is off it wouldn't have any pedal. Also, the little plastic fitting the line goes to is a check valve. If he pulls that out, he should only be able to suck through on side of it. The master cylinder would be the first thing I would replace if the line is connected and the check valve is good cuz it's the cheapest.
The brakes use what called a vacuum booster. The vacuum booser ONLY works while the engine is running. Therefore, with the engine off, there is no boost to the brakes. If the brake pedal is going to the floor, there is air in the brake lines, or brake cylinders (at the wheels). Air compresses as the brake fluid pushes into the brake system and alows the pedal to go to the floor. 1) Look at the inside of all four wheels for a fluid leak. 2) Check the brake fluid resevior to see if it's empty. 2a) If it's empty, he needs to have the brakes replaced or find out where it leaked out from. 3) He WILL need to bleed all four wheels to get the air out of the system in this sequence: Right rear, left rear, right front, left front.) Don't let the master cylinder go dry, otherwise he'll have to bleed it all over again.
