QX80 Spongy Brakes & Fluid Flush - Overdue Maintenance?

Hi David L.,

Your observation of a spongy brake pedal on your 2018 Infiniti QX80, especially at 65,000 miles without a brake fluid flush, is a classic symptom of old or contaminated brake fluid. This is a critical maintenance item that's often overlooked.

Here's why a brake fluid flush is important and what you should do:

1. Brake Fluid's Role: Brake fluid is hygroscopic, meaning it absorbs moisture from the air over time. This moisture contaminates the fluid and significantly lowers its boiling point. When brakes are used heavily, the fluid heats up, and if it boils, it creates vapor bubbles in the brake lines.
2. Spongy Pedal Cause: Unlike incompressible fluid, these vapor bubbles are compressible. When you press the brake pedal, you're compressing these bubbles instead of directly transmitting force to the calipers, resulting in that 'spongy' feeling and reduced braking effectiveness. In extreme cases, this can lead to total brake failure.
3. Corrosion: The absorbed moisture also promotes corrosion within the brake lines, calipers, and ABS components, leading to expensive repairs down the line.
4. Service Interval: For your Infiniti QX80, it's generally recommended to flush and replace the brake fluid every 2 years or 30,000 miles, whichever comes first. At 65,000 miles and likely 5-6 years old, your fluid is almost certainly overdue.
5. Fluid Type: Ensure your QX80 uses DOT 3 or DOT 4 brake fluid, as specified in your owner's manual. DOT 4 has a higher boiling point and is often preferred for performance and heavier vehicles.
6. DIY vs. Shop: A brake fluid flush can be a DIY job for those with the right tools (bleeder wrench, clear tubing, catch bottle, and possibly a pressure bleeder or a helper for two-person bleeding) and a good understanding of the process. However, it's crucial to ensure no air enters the system, and that all old fluid is thoroughly purged. Given the importance of brakes, and the complexity of modern ABS systems, many owners prefer to have this service done by a professional shop. They have specialized equipment (like pressure bleeders) that make the job faster, more thorough, and minimize the risk of introducing air.

When to See a Shop:

• Immediately, as spongy brakes are a safety concern. Do not delay this service.
• If you're not confident in performing the flush yourself, or if you don't have the proper tools.
• If the spongy feeling persists after a professional flush, indicating a potentially more serious issue like a failing master cylinder, brake line leak, or air trapped deep within the ABS module (which sometimes requires dealership-level diagnostic tools to cycle the ABS pump for bleeding).