There is air or water in the brake lines. Flush and bleed the system.
Motor vehicle brakes are usually hydraulic, which means that the brake pedal is basically a pump. pushing the brake pedal pumps some brake fluid through pipes and hoses out to the brakes at the wheels, activating the brake pads. The pipes and hoses are also referred to as "lines", and they can spring leaks if they get too old, damged and worn.
Pedal pumps up fine, but when you run the engine, the brake booster applies more force to the lines. Thus compressing any air that may be in there. You will need to bleed the brakes more. I sometimes bleed the brakes with the engine running to correct this.
sounds like you still have air in brake system ,
It means that your Antilock Brake System is not working. The ABS system works when the system senses that the vehicle is going to go into a skid. While you hold your foot down on the brake pedal, the ABS system pumps the pedal to keep the vehicle straight while stopping. Chances are that you have a bad wheel sensor.
the traction light comes on telling you there is a low traction condition, not that the system needs service. the anti-lock brake system is the noise you hear. it is a series of hydraulic pumps that is cycling the brake pressure on the locking wheel. that is also what you feel on the pedal. the system is working as it should.
asuming the brakes are fine. what we have is servo assistance all cars have brake servo's these unit's aid the driver to operate the brakes because with out servo assistance you could not stop the car on your own. how ever if you must check your brakes turn the car off now pump the brake pedal after 3 or 4 maybe 5 pumps of the pedal it should become solid if it not then get them looked at. but lets say they are now with the pedal feeling solid hold the pedal down as hard as you can now start the car now as you start the car the pedal should go down pretty much all the way down this is the servo kicking in which is great but if the pedal does not go down the servo needs looking at. and this goes for all cars .
I would recommend the place you bought your car, or if it doesn't sell them, you should probably check out eBay I've seen some brake vacuum pumps on there.
If you are sitting at a light with your foot on the brake and you feel the brake pedal slowly sink to the floor but it pumps back up and the brake reservoir stays full, you have a bad master cylinder. -OR, if the brake reservoir gradually lowers every day and you have to keep topping up the fluid. You check each wheel and they are all clean. -Then looking carefully at the master cylinder one day, you see the stains on the front of the booster - - -
I had same proble with my car just today. Mechanic asked me to replace brake boosters and also might be need to replace perportional valve. These parts are only available from a dealer and because of weekened i was`t told that how much does it going to cost me.
After changing the brakes the first few times you press on the brake pedal it will go to the floor; that's because the calipers haven't been pushed back to position. Remember that you had to retract the calipers completely before you could put in the new brake pads. Sometimes it takes a few pumps before the calipers are back in position. Make certain that the brake fluid is all the way up, then bleed the brakes again, and watch that fluid level. If it goes low for just one pedal push then you'll suck air again and you'll have to start over. Just one bubble of air in the brakes will cause trouble.
Yes, there are stores that sell vacuum pumps or brake bleeding kits. Sears currently sells a kit for $99. Harbor Freight Tools has it for sale for $29.
Usually, too many pumps on the gas pedal, especially back in the days of carburetors.