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Spongy Brake Pedal on 2016 Infiniti Q70, No Leaks

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Amanda S. · rep 0 · May 22, 5:06 AM · 1 replies · solved · Question

Vehicle: 2016 Infiniti Q70 3.7 Luxe

Hi everyone,

I've noticed a really spongy brake pedal on my 2016 Infiniti Q70 3.7 Luxe lately. It feels like I have to push the pedal much further down than usual to get the car to stop, and it doesn't feel firm at all. There's no grinding or squealing, and I don't see any visible fluid leaks around the calipers or master cylinder.

I had the brake fluid flushed about a year and a half ago, and the car has 85,000 miles on it. The brake pads still have plenty of life left. It's making me a bit nervous driving it.

What could be causing this spongy pedal feel without any obvious leaks? Could it be air in the lines, or something more serious? Any insights would be great!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:06 AM

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ClearTheCode admin answer:

A spongy brake pedal without visible leaks is a concerning issue that needs prompt attention, as it directly impacts your vehicle's stopping power. While the absence of leaks is good, it doesn't rule out several critical problems.

Common Causes of a Spongy Brake Pedal (No Visible Leaks):

  • Air in the Brake Lines: This is the most common cause. Even after a flush, air can sometimes remain in the system, or it could have entered through a very small, intermittent leak that isn't obvious.
  • Failing Master Cylinder: The master cylinder is responsible for pressurizing the brake fluid. If its internal seals are worn, fluid can bypass the piston, leading to a loss of pressure and a spongy pedal. This often presents as the pedal slowly sinking to the floor when held down.
  • Worn or Damaged Brake Hoses: Over time, rubber brake hoses can swell internally or degrade, leading to a 'ballooning' effect under pressure, which absorbs pedal force and makes the pedal feel soft.
  • Brake Caliper Issues: A sticking caliper piston or a faulty bleeder screw that allows air in can also contribute to a spongy feel.
  • Contaminated Brake Fluid: While less common for a direct spongy feel, old or contaminated fluid can boil under extreme conditions, creating air bubbles.
  • ABS Module Malfunction: In rare cases, an internal issue with the ABS hydraulic control unit can cause a spongy pedal, though this is often accompanied by ABS warning lights.

Troubleshooting Steps:

  1. Bleed the Brakes: The first step is typically to perform a thorough brake bleed, ensuring all air is removed from the system. This should be done starting from the wheel furthest from the master cylinder and working inward.
  2. Check for Pedal Sink: With the engine off, press and hold the brake pedal firmly for about 30 seconds. If the pedal slowly sinks towards the floor, it's a strong indicator of a failing master cylinder.
  3. Inspect Brake Hoses: Visually inspect all rubber brake hoses for any signs of bulging, cracking, or damage.

When to See a Shop:

  • Immediately: A spongy brake pedal is a safety hazard. Do not delay in getting this inspected. If the pedal sinks to the floor, or if braking performance is significantly reduced, avoid driving the vehicle.
  • If Bleeding Doesn't Help: If a thorough brake bleed doesn't restore a firm pedal, it's crucial to have a professional diagnose the master cylinder, brake hoses, and other hydraulic components. They can perform pressure tests and further diagnostics to pinpoint the exact cause and ensure your braking system is safe.
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