Spongy Brakes on 2016 Outlander Sport - Time for Fluid Flush?

ClearTheCode admin answer:

A spongy brake pedal on your 2016 Mitsubishi Outlander Sport GT, especially if the brake fluid has never been flushed, is a classic symptom of old, contaminated brake fluid or air in the system. Brake fluid is hygroscopic, meaning it absorbs moisture over time, which significantly degrades its performance.

Causes of Spongy Brake Pedal:

• Moisture Contamination: Water in the brake fluid lowers its boiling point. During heavy braking, the fluid can boil, creating vapor bubbles (air) in the lines. Since vapor is compressible, the pedal feels spongy.
• Air in the System: Air can enter the system through leaks, improper bleeding, or if the master cylinder reservoir runs low. Like vapor, air is compressible and causes a spongy feel.
• Worn Master Cylinder: Less common, but a failing master cylinder can allow fluid to bypass internally, leading to a spongy pedal that might slowly sink.
• Worn Calipers/Wheel Cylinders: Internal seals can wear, causing fluid bypass or leaks.
• Damaged Brake Hoses: Swelling or deterioration of flexible brake hoses can also affect pedal feel.

When to See a Shop: If a brake fluid flush doesn't resolve the issue, or if you notice any fluid leaks, significant loss of braking power, or if you're uncomfortable performing brake maintenance, it's crucial to take your vehicle to a professional mechanic immediately. Braking system issues are safety-critical.

DIY Considerations and Recommendations:

1. Brake Fluid Flush Interval: Mitsubishi typically recommends inspecting brake fluid every 15,000 miles or 12 months, and often recommends a full brake fluid flush every 30,000 miles or 2 years, whichever comes first. At 60,000 miles and potentially 8 years old without a flush, your fluid is definitely overdue.
2. Recommended Fluid Type: Your 2016 Outlander Sport will use DOT 3 or DOT 4 brake fluid. DOT 4 has a higher boiling point and is often preferred, but ensure compatibility if mixing (though a full flush means you're replacing it all). Never use DOT 5 (silicone-based) fluid unless specified, as it's incompatible with systems designed for DOT 3/4.
3. Why a Flush is Important: A flush removes old, moisture-laden fluid and replaces it with fresh, high-performance fluid. This restores the system's boiling point, prevents corrosion of internal components, and improves pedal feel.
4. DIY Difficulty: A brake fluid flush is a moderately difficult DIY job. It requires:
   • A helper to pump the brake pedal, or a specialized brake bleeding tool (e.g., vacuum bleeder, pressure bleeder).
   • Knowledge of the correct bleeding sequence (usually starting with the wheel furthest from the master cylinder).
   • Care to prevent air from re-entering the system.
   • Proper disposal of old brake fluid.
   • If done incorrectly, you could introduce more air into the system or damage components.

Given the safety implications, if you're not experienced with brake system maintenance, it's highly recommended to have a qualified technician perform the brake fluid flush and inspect the entire braking system.