Brake leak question

[57larry]

one of my sons has a 2003 Ford F150 truck. He's been driving it with the brake light on. Now the pedal goes to the floor. checked the master cyl, it was empty, he filled it up and still no pedal. truck has 4 wheel disc & master cyl booster. looked the truck over, no leaks, nothing on the ground. Your thoughts please

[chimp koose]

Leak may be out the back of the master cyl. If master was empty then it needs to have the master cyl bench bled and then a complete bleed of the system .

[kb426]

Anytime the master has been emptied, it will have to be bled 1st. You can bleed it on the truck by undoing the lines  one at a time starting with the farthest away from the firewall 1st. Many of those masters have a bleeder above both brake lines on the cylinder. If that is the case, bleed it 1st before the two out going lines. My guess is you will have to fill the system to see where the fluid is going. I would look at the firewall to see if it ran under the carpet as one of the possibles.

[57larry]

thanks guys

[WZ JUNK]

I had one once that was leaking into the vacuum booster from the front of the master cylinder, and then being sucked through the engine.  When it got really bad, you could smell it in the engine exhaust.

[57larry]

bled the master cyl. that did the trick

[39deluxe]

But there is still the question as to where the fluid went. Keep a close eye on it.

Tom