Hi guys and gals, I was driving to work the other morning and when i applied the brakes, i could feel the brake pedal slowly going to the floor when i hit the brakes. It doesnt do it all the time, but i would say every 6 or 7 times the brakes are applied. Would the booster be causing this?? as there is no sign of fluid under the car, and the resivoir is full. Any help would be appreciated. James.
Forgot to mention my van is a 1993 glx starwagon. Thanks again.

sounds like it is the brake master cyl (booster)

I've had that problem on my old cars (honda crx, typeR)
ended up getting the master cyl rebuilt and was all good after.

More likely air has entered your system which simply needs bleeding out again. Ensure the reservoir is full. Start at the wheel furthest from the reservoir, place a piece of clear plastic tube of suitable diameter on the bleed nipple outlet next to the in brake line. Using typically a 10mm spanner prepare to loosen the the bleed nipple after someone else has pumped the brake pedal until it is hard thus any air at that wheel will be compressed and in the vicinity of the bleed nipple and ensure they hold the pedal down as the pedal goes to the floor. Watch the tube when you loosen the bleed nipple and observe if air bubbles accompany the outflow of fluid as the pedal lowers to the floor then lock off the bleed nipple and have your helper pump the pedal again until hard. If air bubbles were present repeat the procedure until they are no longer present. Remember to keep topping up the hydraulic fluid reservoir which is located at the right hand end of the dashboard console accessible with the drivers door open. If no air present move to the next furthest wheel from the reservoir and repeat the bleed procedure until all wheels have been bled and the reservoir topped up. Good luck.