Brake Pedal Goes To Floor After New Master Cylinder

Encountering a sinking brake pedal after installing a new master cylinder can be alarming and hazardous. This guide aims to demystify the typical causes of this dilemma and provide practical solutions.

👀Look at this: Essential Guide to Master Brake Cylinder Failure Symptoms

Troubleshooting the Issue

Brake Pedal Goes To Floor After New Master Cylinder Troubleshooting the Issue
Brake Pedal Goes To Floor After New Master Cylinder Troubleshooting the Issue

When a brake pedal sinks post-master cylinder installation, several culprits might be at play:

  • Faulty Installation Techniques: An improperly installed master cylinder can fail to generate the necessary pressure, leading to a sinking pedal. This may stem from incorrect procedures, use of damaged components, or improper fluid levels.
  • Flawed Master Cylinder: The issue might also lie within the master cylinder, possibly due to manufacturing flaws or damages incurred during shipping or fitting.
  • Air Trapped in Brake Lines: Air within the brake lines can significantly diminish braking pressure, as air compressibility hinders effective force transfer.
  • Obstructed or Impaired Brake Lines: Blockages or damage within the brake lines can impede fluid flow, contributing to the problem.

📢Read also: C5 Corvette Brake Master Cylinder

Identifying the Root Cause

To pinpoint the issue:

  1. Check and, if necessary, replenish the brake fluid.
  2. Examine the master cylinder for any signs of damage. Replace if needed.
  3. If the master cylinder seems intact, purge the brake lines using a brake bleeder kit to eliminate trapped air.

🚨You may be interested in: Brake Master Cylinder Brace

Rectifying the Problem

Upon diagnosing the cause, you can embark on the repair process. This may involve:

  • Reinstalling the master cylinder correctly if installation errors are detected.
  • Replacing a defective master cylinder.
  • Purging air from the brake lines, which entails:
    • Parking on a flat surface.
    • Running the engine briefly.
    • Opening the hood to access the master cylinder reservoir.
    • Topping up the brake fluid.
    • Using a brake bleeder on each caliper’s bleeder screw.
    • Having an assistant depress the brake pedal fully.
    • Opening and closing each bleeder screw in succession ensures clear fluid flow.
    • Checking and adjusting the fluid levels post-bleeding.
    • Testing the brakes for proper function.

👀Look at this: Brake Line Won’t Thread Into Master Cylinder


A sinking brake pedal post-master cylinder replacement demands immediate attention. By following the outlined steps, you can address the issue effectively.

Proactive Measures for the Future

To prevent recurrence:

  • Opt for professional installation of the master cylinder.
  • Adhere strictly to manufacturer guidelines during installation.
  • Regularly monitor and maintain brake fluid levels.
  • Schedule routine brake line bleeding every two years or after 25,000 miles.

Leave a Comment

We use cookies in order to give you the best possible experience on our website. By continuing to use this site, you agree to our use of cookies.