If your vehicle has a vacuum brake booster the brake fluid may be entering the vacuum booster with no visibly spots on ground. To check remove rubber hose usually about 3/8"-5/8" in diameter depending on model of vehicle, look inside of hose to see if it is wet, if so the Master Cylinder needs to be replaced.
Is the brake fluid level low in your brake master cylinder in the engine compartment ?
Your brake fluid is how the brake system converts mechanical force of your foot on the brake pedal, into hydraulic force that applies your brakes. Without fluid, your hydraulic brakes will not function.
In the brakes.
Brake Fluid.
Check the brake fluid reservoir, it may be low on brake fluid indicating it is time to have the brakes inspected.
Open brake fluid reservoir for the brakes - make sure it is full of brake fluid - put lid back on reservoir then pump the brakes then hold the brakes on - have someone open the bleed screw on the brakes and let the air and oil out and close it again quickly and repeat until the air bubbles stop in the brake fluid, also checking to make sure you do not run out of brake fluid before you finish bleeding the brakes.
No but, the brake fluid level will drop as brake pads/linings wear.
Sticking caliber. Flush the brake system and install fresh brake fluid, then bleed the brakes. If that does not help, replace both calibers and brake pads on the axle where the brakes are grabbing.
Siphon it out. Do not drive or pump the brakes. Replace the brake fluid. This will cause the brakes to fail.
If you replace any brake component that breaks the brake fluid seal or you let it get very low of brake fluid, yes, you must bleed the brakes.
The hose that your brake fluid flows through when u mash the brakes
A few reasons. Fluid has a much higher density, and makes it easier to apply more force to the brakes. Fluid is much easier to contain and refill. No special equipment is necessary to fill a brake fluid reservoir.