wild boar

The pedal is doing as you say alsalih, and the master cylinder is not leaking. I agree that it is probable that there is air in the lines,but the only thing I have not done is bleed the abs unit, how do I do this? ps I know that the vacuum system is working ok, as I have had the pipe of the booster and it is sucking like a Monika! :D

Please help me! I have a 1997 LS400 and I am having some really annoying problems with excess travel in the brake pedal. I took the car for its annual roadworthiness check (MOT here in the uk), and it failed on excess brake pedal travel. The brake balance and efficiency were both ok. The mechanic who tested the car said that it could be either that the pads on the car were worn, or the master cylinder was bust. So I took the car home and checked through the system myself, what I found confused the hell out of me. When the car is not running the brake pedal feels absoluty fine, nice and firm. If you then start the car, the pedal sinks easily to the floor. So far I have put new pads on the front, checked the rear pads (ok), and rebuilt the master cylinder with a Lexus supplied kit (£100/$170! for the internals only). I have blead the brakes as it instructs in a workshop manual that I have. Can anyone suggest what the problem may be? All that I can think of, is that it is the brake servo (brake booster?).