Description
Main brake master cylinder Bosch for Citroën C4 and Peugeot 307.
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.
