Product Overview

High-quality Bosch brake master cylinder designed for Citroën and Peugeot compact models. This direct-fit hydraulic unit restores firm pedal feel and reliable pressure distribution to the braking system. Ideal for professional garages and experienced DIY mechanics who search by part number — common references include 0204254242 and 4601V1. Replacing a worn master cylinder resolves symptoms such as a sinking or spongy brake pedal, internal leaks and loss of braking efficiency.

Key Advantages

• Precision machined components and durable seals for long service life.
• Compatibility with common Citroën/Peugeot brake systems on C4 / C4 II and 307 / 308 models.
• Fast identification by part numbers (handy for workshop parts ordering and inventory).
• Designed to meet the performance demands of modern hydraulic braking systems.

Technical Information

• Manufacturer: Bosch
• Model: Citroën C4, Citroën C4 II, Peugeot 307, Peugeot 308
• Product Codes: 0204254242, 4601R1, 4601T2, 4601V1, 4601V0
• Other Numbers: 204254242 (alternative formatting)

Function And Symptoms Of Failure

The brake master cylinder converts pedal force into hydraulic pressure that operates the calipers and wheel cylinders. Typical failure modes include internal seal wear or collapse, contamination from degraded brake fluid, and corrosion of internal bores. Signs that indicate replacement is required: a gradually sinking brake pedal, a soft or spongy pedal feel, visible fluid leaks at the unit or connections, and uneven braking. Left unaddressed, a failing master cylinder reduces braking performance and can compromise vehicle safety.

Installation Recommendations

Installation should be carried out by a qualified technician or a competent DIYer familiar with brake systems. Basic replacement steps:

• Prepare the vehicle on a level surface and secure it with the parking brake and wheel chocks.
• Remove excess brake fluid from the reservoir using a suitable tool to avoid spills.
• Carefully disconnect brake lines with a flare-nut wrench and cap the lines to prevent contamination.
• Unbolt the master cylinder from the brake booster/firewall and remove the unit.
• Fit the new master cylinder, torque fasteners to manufacturer values, reconnect lines and refill the reservoir with manufacturer-recommended brake fluid.
• Bench-bleed the new unit before installation and perform a full hydraulic bleed of the braking system after fitting to remove air.
• Check for leaks and verify pedal firmness during a low-speed test drive.

Safety Notes: Brake system work affects vehicle safety. Use correct tools, replace contaminated fluid, and follow the vehicle manufacturer’s procedures. If unsure, have the replacement and bleeding done by a professional workshop.

Why This Part Fails Most Often

Master cylinders commonly fail due to ageing seals and contamination. Moisture in brake fluid accelerates internal corrosion and seal deterioration. Over time, abrasive particles and degraded fluid compromise seal surfaces, causing internal leaks and loss of pressure. Heavy or aggressive braking, neglected fluid changes, and prolonged exposure to moisture increase the risk of premature failure.

Compatibility And Searching Tips

This part is frequently searched by the listed part numbers — include 0204254242 and 4601V1 in your lookup to find exact matches. It fits the Citroën C4 (including C4 II) and Peugeot 307 / 308 ranges where this Bosch master cylinder specification is used. Always verify fitment against the vehicle model and year using the part numbers provided.

Final Notes

Choosing a correctly matched Bosch master cylinder ensures reliable braking response and workshop efficiency. Order by part number for fast identification and trust the robust construction to deliver consistent performance under everyday and service conditions.

High-quality Bosch Main Brake Cylinder designed for Citroën C4 and Peugeot 307/308 models. This direct-fit replacement restores firm pedal feel and safe braking performance. Suited for both professional workshops and competent DIY enthusiasts, the unit matches OEM fitment and mounting points for straightforward installation. Commonly sought by part number, this cylinder helps eliminate symptoms such as a spongy brake pedal, internal fluid leaks, or loss of hydraulic pressure.

Technical Information

• Manufacturer: Bosch
• Model: Citroën C4; Peugeot 307; Peugeot 308
• Product Codes: 0204254242, 4601R1, 4601T2, 4601V0
• Additional Numbers: 204254242, 4601V0

Function And Application

The master brake cylinder converts pedal force into hydraulic pressure for the brake calipers and wheel cylinders. It houses pistons and seals that push brake fluid through the brake lines when the pedal is depressed. This Bosch unit is intended as a replacement for vehicles originally equipped with the corresponding Bosch/OEM master cylinder on Citroën C4 and Peugeot 307/308 platforms.

Typical Symptoms Of Failure

• Spongy Or Sinking Brake Pedal: Increased pedal travel or gradual sinking under steady pressure indicates internal seal leakage.
• External Fluid Leaks: Fluid around the cylinder body, reservoir, or brake line connections.
• Brake Imbalance Or Dragging: Uneven braking or partial application when released, caused by internal faults or contamination.
• Warning Lights/ABS Related Issues: Air or contamination in the system may affect ABS modulation; follow correct bleeding procedures.

Why The Part Fails Most Often

Failures are usually caused by age-related wear of rubber seals, contamination of brake fluid (moisture, debris), corrosion of internal cylinder surfaces, or damage from improper bleeding and maintenance. Extended exposure to high temperatures and neglected fluid changes accelerate seal degradation and internal scoring.

Installation And Fitment

Removal And Replacement Tips:

• Secure The Vehicle And Work Safely: Park on level ground, use wheel chocks and jack stands where required.
• Drain Or Extract Brake Fluid From Reservoir To Minimize Spillage; Protect Paintwork From Fluid.
• Disconnect Brake Lines Using A Flare-Nut Wrench To Avoid Rounding Fittings; Cap Lines To Prevent Contamination.
• Unbolt The Master Cylinder From The Brake Booster/Mounting Bracket And Remove Carefully.
• Install New Unit, Reconnect Lines And Reservoir Hoses, And Tighten To Manufacturer Torque Specifications.
• Fill With Fresh DOT Brake Fluid Specified By Manufacturer (Typically DOT4 For These Models) And Perform Proper Bleeding.

Bleeding: Follow The Manufacturer’s Recommended Bleeding Sequence And Procedure, Especially On Vehicles With ABS/ESP. Improper Bleeding Can Leave Air Trapped In The System And Affect Braking Or ABS Performance.

Recommendation For Installation

• Always Use Fresh, Correct-Spec Brake Fluid And Replace Fluid If Contaminated.
• Inspect Brake Lines, Hoses, Calipers, And Wheel Cylinders While Replacing The Master Cylinder; Replace Damaged Components.
• Use New Sealing Washers Or Crush Washers Where Required And Torque Fasteners To OEM Values.
• After Installation, Test Brake Pedal Feel At Low Speed In A Safe Area Before Normal Driving.

Suitable For

Direct Fit For Citroën C4 And Peugeot 307 / 308 Models Equipped With The Corresponding Bosch Master Cylinder Part Numbers. Often Searched By Part Number For Fast Identification.

Why Choose This Unit

Bosch Quality Assurance, OEM-Compatible Fitment, And Durable Materials Make This Master Cylinder A Reliable Choice For Restoring Brake System Performance. Ideal For Garages And Skilled DIYers Looking For A Straightforward Replacement That Matches Original Specifications.

This Bosch master brake cylinder is a direct-fit replacement part designed for Citroën C4 and Peugeot 307 models. Built to restore hydraulic pressure and pedal feel, it is suitable for professional workshops and experienced DIYers who maintain or repair PSA group braking systems. Common search terms include Bosch master cylinder, Citroën C4 master cylinder, Peugeot 307 master cylinder and product codes 0204254242 / 4601R1 / 4601T2 / 4601V0.

How It Works

The master cylinder converts mechanical force from the brake pedal into hydraulic pressure that operates the wheel brakes. It contains pistons and internal seals that pressurize brake fluid and feed it through the brake lines to calipers or wheel cylinders. Proper sealing and free piston movement are essential for consistent pedal feel and safe braking performance.

Replacement Procedure

Replacement requires basic workshop tools and knowledge of hydraulic systems. Typical steps:

• Park vehicle on level ground, secure wheels and relieve any residual system pressure.
• Protect painted surfaces and collect old brake fluid—brake fluid is corrosive.
• Disconnect brake lines from the master cylinder (plug lines to avoid contamination and fluid loss).
• Unbolt the master cylinder from the brake booster/vehicle body and remove the old unit.
• Bench-bleed the new master cylinder before installation to remove air from internal circuits.
• Fit the new unit, torque fasteners to manufacturer values, reconnect brake lines and refill with recommended brake fluid.
• Perform a full system bleed (preferably pressure or vacuum bleed) until no air remains and pedal feel is firm. Check for leaks and proper operation.
• Dispose of old fluid according to local regulations and test drive carefully to confirm braking performance.

Installation Recommendations

• Bench-Bleed Before Installation: Always bench-bleed a new master cylinder to remove trapped air inside the housing so the system bleed on the vehicle is faster and more effective.
• Use Manufacturer-Specified Brake Fluid: Use the PSA-specified fluid type (commonly DOT4 for these models) and replace fluid if contaminated or aged.
• Protect Components: Avoid getting brake fluid on painted surfaces; it will damage paint. Use suitable plugs to prevent contamination of brake lines.
• Bleeding Sequence: Follow the correct bleeding order for the vehicle (usually farthest wheel first) and confirm pedal firmness before driving.
• Safety: Wear eye protection and gloves. If you are not confident with hydraulic systems, have the replacement performed by a qualified technician.

Most Common Failure Reasons

Master cylinders typically fail due to seal wear, internal corrosion, or contamination of brake fluid. Symptoms include a soft or sinking brake pedal, external fluid leaks around the unit, uneven braking, or air ingress into the hydraulic circuit. Rubber seals and pistons degrade over time, accelerated by moisture-contaminated fluid and lack of regular fluid changes.

Technical Information

• Manufacturer: Bosch
• Model: Citroën C4; Peugeot 307
• Product Codes: 0204254242, 4601R1, 4601T2, 4601V0
• Additional Numbers: 204254242

Why Choose This Part

As a direct replacement, this Bosch master cylinder restores original hydraulic performance and pedal feel. It is aimed at mechanics and competent DIYers who require reliable braking operation and compatibility with Citroën C4 and Peugeot 307 brake systems. Including the correct product code in your search increases the chance of finding an exact-fit unit quickly.