Cardone Select 13-4007 New Brake Master Cylinder Quality that meets or exceeds OE fit, form and function Aluminum casting units designed to exact tolerances for proper fit and function Castings protected by anodized coating to resist rust and corrosion Testing that exposes seals to extreme temp changes to ensure reliability in the harsh 'underhood environment' Exceptionally smooth bore that minimizes wear caused by every brake stroke resulting in longer service life Check booster for a defective push rod seal. If this seal is bad, it could drain the brake fluid out of the master cylinder. The master cylinder is working correctly. Check for a faulty brake booster or frozen wheel cylinder/caliper. Check booster for a defective push rod seal. If this seal is bad, it could drain the brake fluid out of the master cylinder.