Most likely causes are a rusted metal brake line, cut or hole in rubber brake hose or possibly you have a wheel cylinder leaking. No matter the cause its very important to get it fixed because its likely that at some point your brakes will go out completely.
It all depends on what part is leaking what fluid. Brake cylinder would leak brake fluid. Axle seal would leak gear oil.
where is it leaking from?
brake fluid leaking from a brake drum indicates the brake slave cylander on that wheel is leaking and needs to be replaced you will not see the actual leak with out removing the brake drum
Brake fluid in a Toyota Sequoia could be leaking from several places. Check the wheel cylinders first as they are a common place to leak.
Seal in brake caliper is leaking and needs replacement Flexible brake line to the caliper is leaking and needs replacement
Replace the leaking part
There would be break fluid OUTSIDE of the lines and reservoir
take it to the shop to get fixed!
Worn brake shoes or pads. A leaking brake pipe. Low brake fluid. Air in the brake fluid pipe.
If a Mazda MPV is leaking yellow fluid then it is possible that the fluid is brake fluid. It is best to take the car to a mechanic right away.
You might be out of brake fluid. Our rear wheel cylinder was leaking and ran ours out of fluid and the light came on.
If the fluid leaking into the rear tire is not brake fluid then it comes from the differential. It means you have a leaking seal. It means you are losing differential fluid. When the fluid is gone or gets low, you will lose your differential, the gears will strip, you will hear a horrible grinding sound, the rear wheels will lock up, and you will be stuck with the vehicle stopped wherever you are. Hopefully, it will not be in the middle of an Interstate highway with traffic screaming past at 80 miles an hour.