empty, should i put same brake fuild for both tanks? whats the difference why they are seperate ?
Take the vehicle to mechanic NOW! If brake fluid almost empty it means you have a leak somewhere and more the likely air in the brake lines. You will need to get the leak fixed, and brakes bleed before driving again. Otherwise you're risking your life and the life of the guy in front of you!
There are two tanks because you have two separate braking systems on the car--usually hooked up on what is called a dual diagonal system. The idea behind this is that if you spring a leak or otherwise have a problem with either system you do not lose all braking capacity. Usually each of the systems controls the front brake on one side of the car and the rear brake on the opposite side so that you will not have a torque effect when you hit the brakes after one side has failed--hence dual diagonal. Now, in that both reservoirs are being drained, I would guess it is fairly likely you have had a master cylinder failure and this would be evidenced by wet looking areas below the tank which have probably gathered up a fair amount of grime by now. Your other respondant are correct in pointing out that if you are losing brake fluid fairly suddenly and rapidly, you need to attend to this promptly, as if you lose your brake fluid the brakes will cease to function.
Those are fine answers listed above, however they do not go into enough detail. The brake master cylinder is designed to hold just the right amount of brake fluid for your brake system. There are two things to note. 1) As the brake pads wear out, the calipers piston has to move farther out to press on the brake pads. As the piston moves farther out, the area behind the piston becomes filled with more fluid from the master cylinder, and the level of fluid in the master cylinder goes down. When the fluid level in the master cylinder gets too low, a light should come on indicating that your brake fluid is low. That does NOT mean you need to add brake fluid. It means your brake pads are VERY close to being worn out. 2) If you add brake fluid today, and have your brakes done tomorrow, when the mechanic compresses the caliper piston ALL the excess brake fluid is going to spill out of the master cylinder all over the engine compartment and make a huge mess. Not to mention ruining your car. Just a note: Brake fluid does not evaporate. So, unless you have a leak, NEVER add brake fluid. Have your brakes serviced.
