As I was driving my '84 F-150 today, I put on the brakes and the pedal went almost all the way to the floor. After pumping the pedal a couple of times, it returned to normal. I pulled off the road and checked the reservoir -- it was full. This kept happening until I finally got home. Any ideas? Could it be a vacuum line or something simple like that?
Thanks, Okie
Sounds like the seal in the rear of the master cylinder has failed. If you have a brake fluid trailer on the front face of the brake booster, it is a sure bet. In any case, if you cannot find any external leak(s), replace the master cylinder ASAP. They are not expensive and are readily available in most places these days.
Still looking for help.
Okie
Master cylinder is kaput.
i got a 93 taurus and had a similar problem... thought it was the mast. cylinder also.. brakes worked fine about 20 minutes after driving in stop and go city traffic to work the brakes went to the floor.. you pump it up and it would work.. after the car cooled off it would work fine also.. thought it was one of the seals being messed up with the heat of the engine under the hood while driving.... was changing the rear brake shoes and discovered that the passenger rear brake spring were not pulling the shoe back like it should when you take your foot off the brakes... discovered that the meta rod that comes from inside the sides of the wheel cylinder were moving to the side as the brake shoe was not there to guide it and would come out too far: results more fluid went into this wheel cylinder and the pedal would go to the floor... never had a leak anywhere on the car.... fix was some $5.00 for the rear brake shoe springs at auto zone..(new spring pack).... never had a problem since.. that was about 8 yrs. ago.. the heat from the brakes was messing up the spring tension on the metal in the springs....
Bleed the brakes. Check for leaks. It has air in the lines.
If it only happens when you have been driving for a while then it is water (which boils from the heat and turns into a gas). Liquids cannot be compressed, gasses can.
Either way you need to bleed them.
Empty out the brake fluid from the reservior and clean it with a rag, an old t-shirt or something that will not leave any fluff behind, and fill back up with clean fluid.
Crack the bleed nipple at the furthest point from the reservior, furthest in terms of the longest brake line, and get someone to depress the brake pedal. Close the nipple before allowing the person to release the pedal. Repeat this 7 or 8 times and check the level in the reservior. Keep it topped up. Keep pumping the old fluid through the first nipple until clen fluid comes out.
Repeat this for each of the nipples, going from furthest to nearest the reservior, until each has clean fluid coming out of them.
Also, when was the last time you checked the brakes? Are the rear brakes drums? Check the wheel cylinders for leakage by pulling back, with clean hands, the rubber dust covers. If brake fluid comes out they are leaking and need to be replaced.
Scott.
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