Hydraulic master cylinder consists of a fluid reservoir along with a double cylinder and piston assembly. In your Acura TL, a new innovation in the brake systems is employed to heighten safety. A double type cylinder is designed to separate the front and rear braking systems hydraulically in case of a leak. The  master cylinder converts mechanical motion from the pedal into hydraulic pressure within the lines. This pressure is translated back into mechanical motion at the wheels by either the wheel cylinder or the caliper. Steel lines carry the brake fluid to a point on the Acura's frame near each of the vehicles wheels. The fluid is then carried to the calipers and wheel cylinders by flexible tubes in order to allow for suspension and steering movements. In the disc brake systems, the cylinders are part of the calipers. At least one cylinder in each caliper is used to force the brake pads against the disc.

All  Acura TL's Master Cylinder pistons employ some type of seal, usually made of rubber, to minimize fluid leakage, a rubber dust boot seals the outer end of the master cylinder against dust and dirt. the boot fits around the outer end of the piston on disc brake calipers, and around the brake actuating rod on wheel cylinders. When at rest the entire system, from the pistons in the master cylinder to those in the wheel cylinders or calipers, is full of brake fluid. Upon application of the master brake pedal, fluid trapped in front of the master cylinder piston is forced through the lines to the wheel cylinders. here it forces the pistons outward, in the case of drum brakes, and inward toward the disc, in the case of disc brakes. The motion of the master cylinder pistons is opposed by return springs mounted outside the cylinders in drum brakes, and by spring seals, in disc brakes. Upon release of the brake pedal a spring located inside the master cylinder immediately returns the master cylinder to the normal position.The master cylinder pistons contain check valves and the master cylinder has compensating ports drilled in it. These are uncovered as the pistons reach there normal position. The Acura TL master cylinder piston check valves allow fluid to flow toward the wheel cylinders or calipers as the pistons withdraw. Then as the return springs force the brakes pads or shoes into the released position, the excess fluid reservoir through the compensating ports it is during the time the pedal is in the relished position that any fluid that has leaked out of the system will be replaced through the compensating ports.  

•  A double type  Master cylinder is designed to separate the front and rear braking systems .