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Spongy Brake Pedal After QX50 Pad Replacement

0

Mike T. · rep 0 · May 22, 5:08 AM · 1 replies · solved · Question

Vehicle: 2022 Infiniti QX50 Essential

Hey everyone,

I recently changed the front brake pads and rotors on my 2022 Infiniti QX50 Essential, which has about 30,000 miles on it. I followed a guide, compressed the calipers, and put everything back together. I made sure to pump the pedal a few times before driving.

Now, the brake pedal feels really soft and spongy. It goes down a lot further than it used to before the brakes really engage. The car still stops, but it doesn't feel right at all. I'm pretty sure I didn't open any lines, but could air have gotten into the system somehow? Do I need to bleed the brakes, and if so, what's the best way to do it on a QX50?

Thanks for any advice!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:08 AM

0

ClearTheCode admin answer:

A spongy brake pedal after a pad and rotor replacement is a classic symptom of air in the brake lines. Even if you didn't open any lines, air can sometimes be introduced when compressing the caliper pistons, especially if the master cylinder reservoir was overfilled and fluid was pushed back too quickly, or if the fluid level dropped too low during the process.

Here's what you should do:

  1. Brake Bleeding: This is almost certainly required. Air is compressible, unlike brake fluid, which causes the spongy feeling. You'll need to bleed the brakes to remove any trapped air.
    • Method: The most common method is a two-person job: one person pumps the pedal while the other opens and closes the bleeder screw at each caliper. Alternatively, you can use a vacuum bleeder or a pressure bleeder (recommended for a single person).
    • Bleeding Order: Always start with the wheel furthest from the master cylinder and work your way closer. For most Infiniti vehicles, this is typically: Rear Passenger -> Rear Driver -> Front Passenger -> Front Driver.
    • Fluid Type: Ensure you use the correct DOT-rated brake fluid (usually DOT 3 or DOT 4 for your QX50). Never mix different types.
  2. Check Fluid Level: Before and during bleeding, ensure the brake fluid reservoir remains adequately filled. If it drops too low, more air will be introduced.
  3. Inspect for Leaks: Double-check all caliper bolts, bleeder screws, and brake lines for any signs of leaks. A loose bleeder screw or a damaged line could also introduce air.

Causes of Spongy Pedal:

  • Air in the System: Most common cause after brake work.
  • Old/Contaminated Fluid: If your brake fluid is old, it can absorb moisture, reducing its boiling point and causing a spongy feel, especially under heavy braking.
  • Master Cylinder Issues: Less likely after just a pad change, but a failing master cylinder can also cause a soft pedal. However, this usually presents with a pedal that slowly sinks to the floor.

When to see a shop:

  • If bleeding the brakes thoroughly doesn't resolve the spongy pedal issue.
  • If you notice any brake fluid leaks after bleeding.
  • If the brake pedal still feels unsafe or if any brake-related warning lights (like ABS or VDC) illuminate on your dashboard. A professional can perform a more advanced diagnostic, including checking the master cylinder and ABS module.
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