58510-2T100 CYLINDER ASSY-BRAKE MASTER Fits K5 Optima 2011-2015

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Product Function Description

The brake master cylinder is the heart of your vehicle's braking system. When you press the brake pedal, this cylinder converts the mechanical force into hydraulic pressure, pushing brake fluid through the brake lines to activate the brake calipers or wheel cylinders at each wheel. This hydraulic pressure is what actually stops your vehicle. For a sedan like the Kia K5 / Optima, a properly functioning brake master cylinder is essential for safe and predictable braking performance. It ensures consistent pedal feel, proper stopping distance, and reliable activation of the ABS system. A failing master cylinder compromises your vehicle's most critical safety system, putting you and your passengers at risk.

When Should You Replace It?

Consider replacing your brake master cylinder if you experience any of the following symptoms: Spongy or soft brake pedal – the pedal feels mushy and travels too far before engaging. Brake pedal slowly sinks to the floor while holding pressure at a stop. Brake fluid leaks visible under the vehicle or around the master cylinder area. Brake warning light appears on the dashboard. Reduced braking power – the vehicle takes longer to stop than normal. Brake pedal feels hard and requires excessive force. Contaminated or dark-colored brake fluid in the reservoir. External leaks from the master cylinder or internal seal failure causing fluid bypass. ABS warning light illuminated along with brake issues. Low brake fluid level without visible external leaks (internal leakage).

Product Specifications

Why Choose This Brake Master Cylinder for Your Kia K5 / Optima?

Direct Fit Replacement – Designed specifically for the Kia K5 / Optima 2011-2015, this cylinder bolts directly to your existing brake booster with no modifications required. Restores Factory Brake Feel – Over time, the internal seals of the original master cylinder wear and allow fluid bypass, resulting in a spongy pedal. This new cylinder restores the firm, confident brake pedal feel that Kia designed for your vehicle. Ensures Safe Stopping Power – A properly functioning master cylinder delivers consistent hydraulic pressure to all four wheels, ensuring predictable braking and shorter stopping distances when you need them most. Dual-Circuit Safety – This master cylinder features a dual-circuit design – if one circuit fails, the other remains operational, providing a backup safety margin. Prevents Costly Repairs – Replacing a failing master cylinder early prevents brake fluid contamination from damaging other brake components like the ABS module and brake calipers. Tested for Quality – Each unit undergoes rigorous testing for leakage, pressure retention, and durability to ensure reliable performance.

Package Contents

1 x Brake Master Cylinder (with integrated reservoir – confirm actual contents before purchase). 

Installation Tips

Important: The brake system is a critical safety system. Professional installation is strongly recommended. Before installation, ensure the vehicle is parked on level ground and securely supported. Remove the brake fluid from the reservoir. Disconnect the brake lines from the old master cylinder – be careful not to damage the line fittings. Remove the mounting nuts and remove the old cylinder. Bench-bleed the new master cylinder before installation to remove internal air – this is a critical step and cannot be skipped. Mount the new cylinder to the brake booster and tighten the nuts to factory torque specifications. Reconnect all brake lines. Fill the reservoir with fresh Kia-approved brake fluid. Bleed the entire brake system starting from the wheel farthest from the master cylinder (right rear, left rear, right front, left front) to remove all air from the lines. Check all connections for leaks after bleeding. Critical Step: After installation, test brake pedal feel – it should feel firm and consistent. A spongy pedal indicates air remains in the system and bleeding must be repeated. Professional bleeding equipment is recommended for best results.

Common Issues with Original Kia K5 / Optima Brake Master Cylinders

Kia K5 / Optima owners often experience brake master cylinder failure due to: Age and mileage – For vehicles from 2011-2015, internal seals naturally harden, shrink, and degrade over time. Brake fluid contamination – Old, moisture-contaminated brake fluid (hygroscopic) causes internal corrosion and accelerated seal wear. High operating pressure – The brake system operates at very high pressures, and seals eventually wear from constant use. Heat exposure – Repeated braking generates heat that accelerates seal degradation. Internal bypass – As seals wear, brake fluid bypasses the seals internally, reducing hydraulic pressure and causing a spongy pedal. This replacement master cylinder is designed to address all these issues with high-quality seals and precision-machined internal components, restoring your Kia's braking system to peak condition.

After-Sales Service & Warranty

We stand behind the quality of our products. This brake master cylinder comes with a 12-month warranty against manufacturing defects. If you have any questions or issues, please contact us and we will respond within 24 hours.

Recommended Related Products

Brake Fluid (Kia/Hyundai DOT-3 or DOT-4) / Brake Booster / Brake Line Flaring Tool Kit / Brake Bleeder Tool / Brake Line Wrenches / Brake Calipers