Cardone 10-2638 Remanufactured Master Cylinder New rubber seals and cups prevent leakage. All rubber meets SAE specifications. Piston assemblies 100% height-gauged to meet or exceed OE performance. Piston bores meet strict micro-finish specifications to eliminate pitting and corrosion. Bleeder kits and instructions provided Every unit is 100% tested to ensure quality and reliability The first step to bench bleeding a step bore is to slowly depress the master cylinder piston, then release slowly and wait 20 seconds before depressing again. NEVER pump piston/pedal with a step bore style master cylinder. Follow the same process on the vehicle. Check booster for a defective push rod seal. If this seal is bad, it could drain the brake fluid out of the master cylinder.