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Spongy brake pedal on 2020 Acadia Denali after pad replacement

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Mike T. · rep 0 · May 22, 3:41 AM · 1 replies · solved · Question

Vehicle: 2020 GMC Acadia Denali

Hello, I recently replaced the front and rear brake pads and rotors on my 2020 GMC Acadia Denali, which has about 55,000 miles. Everything seemed to go smoothly, but now the brake pedal feels really spongy. It goes down quite a bit before the brakes really engage, and it just doesn't feel firm like it used to.

I tried bleeding the brakes using the traditional two-person method, starting with the furthest wheel, but it hasn't made much of a difference. Could there still be air in the lines, or is it possible I damaged something? No warning lights are on, thankfully.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:41 AM

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ClearTheCode admin answer:

A spongy brake pedal after a brake job on your 2020 GMC Acadia Denali almost always points to air in the hydraulic system. Even if you've attempted bleeding, it can be tricky to get all the air out, especially with modern ABS systems. Here's what to consider:

  1. Thorough Bleeding: Re-bleed the brakes, ensuring you follow the correct sequence (typically passenger rear, driver rear, passenger front, driver front). Make sure the master cylinder reservoir never runs low during the process. For some vehicles, a pressure bleeder or vacuum bleeder can be more effective than the traditional method.
  2. ABS Module Bleed: Modern vehicles with ABS (Anti-lock Braking System) sometimes require a scan tool to cycle the ABS pump during the bleeding process. This is often called a 'service bleed' or 'ABS automated bleed' and helps purge air trapped within the ABS hydraulic control unit. If air got into the ABS module, manual bleeding might not be enough.
  3. Master Cylinder Issues: While less common immediately after a pad replacement, if the master cylinder was pushed too far during caliper compression (especially if the reservoir was overfilled and fluid wasn't removed), it could potentially damage the internal seals. However, air in the lines is a much more probable cause.
  4. Brake Fluid Condition: Ensure you used fresh, correct-spec brake fluid (DOT3 or DOT4, as specified by GMC). Old or contaminated fluid can also affect pedal feel.

Diagnostics & When to See a Shop:

  • If repeated manual bleeding doesn't resolve the issue, it's highly recommended to take your Acadia to a professional shop. They have specialized scan tools to perform the ABS service bleed, which is often the solution for stubborn air pockets.
  • While no warning lights are on, a shop can also check for any pending or historical ABS-related diagnostic trouble codes (DTCs) that might not be illuminating the dash light but could indicate an issue (e.g., C0200 for ABS pump motor circuit, though less likely with just a spongy pedal). Driving with compromised brakes is a significant safety risk, so address this promptly.
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