Maintenance Brakes Intermediate
Brake Bleeding: Hydraulic DOT Systems
🔧 Estimated time: 1-2 hours
🔧 Tools Required
- • Bleeder valve wrench (8mm or 10mm typical)
- • Silicone tubing (clear)
- • Container for used fluid
- • Large syringe (optional, for reverse method)
- • Fresh brake fluid (DOT 4 or DOT 5.1)
- • Clean rags
- • Nitrile gloves
- • Safety glasses
📦 Parts/Materials
- • DOT 4 or DOT 5.1 brake fluid (500ml minimum)
⚠️ Safety Warnings
- ! Brake fluid is corrosive - destroys paint and plastics
- ! Wear glasses - fluid severely damages eyes
- ! NEVER mix DOT 5 (silicone) with DOT 3/4/5.1 (glycol)
- ! Do not inhale brake fluid vapors
Difficulty Level Moderate
Easy Moderate Hard
Brake Bleeding: Complete Guide
A brake system with trapped air is dangerous. Bleeding removes air and old contaminated fluid.
When to Bleed the Brakes?
| Symptom | Urgency |
|---|---|
| Spongy lever/pedal | Immediate |
| Excessive travel | Immediate |
| Loss of power | Immediate |
| Dark/cloudy fluid | Schedule soon |
| Every 2 years (preventive) | Regular maintenance |
Types of Brake Fluid
| Type | Base | Dry Boiling Point | Use |
|---|---|---|---|
| DOT 3 | Glycol | 205°C | Cars, basic bikes |
| DOT 4 | Glycol | 230°C | Standard for motorcycles |
| DOT 5.1 | Glycol | 260°C | Racing, intensive use |
| DOT 5 | Silicone | 260°C | Harley (DO NOT mix) |
Traditional Method (Two People)
Procedure
-
Fill the master cylinder reservoir with fresh fluid
-
Person 1: At the lever/pedal
- Pump slowly 5-6 times
- Hold pressure on the last pump
- Announce: “Pressure”
-
Person 2: At the bleeder
- When you hear “Pressure,” open 1/4 turn
- Watch fluid/bubbles come out
- Close the bleeder
- Announce: “Closed”
-
Repeat until no more bubbles appear
⚠️ Critical Rule
NEVER release the lever with the bleeder open
Bleeding Order
Dual Disc Front Brake
- Right caliper (furthest from master)
- Left caliper
Rear Brake
- Rear caliper
Signs of Successful Bleeding
| Before | After |
|---|---|
| Spongy lever | Firm lever |
| Long travel | Short travel |
| Dark fluid | Clear/amber fluid |
| Slow response | Immediate response |
Visual Fluid Inspection
| Color | Condition | Action |
|---|---|---|
| Clear/Amber | New | OK |
| Dark amber | Used | Change soon |
| Brown/Black | Contaminated | Change immediately |
Safety Tip: After any brake work, ALWAYS perform a low-speed test in a safe area.