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2021 CT4 Brake Fluid Flush - What fluid and when?

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Mike T. · rep 0 · May 25, 2:54 AM · 1 replies · solved · Question

Vehicle: 2021 Cadillac CT4 Premium Luxury

Hi all,

I have a 2021 Cadillac CT4 Premium Luxury with about 35,000 miles on it. The brakes feel fine right now, but I'm thinking about preventive maintenance. I've heard that brake fluid should be flushed periodically, but I'm not sure what the recommended interval is for a newer Cadillac like mine.

Also, what type of brake fluid does the CT4 use? DOT3, DOT4, or something else? I want to make sure I use the correct fluid if I decide to have this done. Is this a DIY-friendly job or something I should definitely take to a dealership or trusted independent shop?

Thanks for any guidance!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:54 AM

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ClearTheCode admin answer:

Regular brake fluid flushes are crucial for maintaining the safety and performance of your 2021 Cadillac CT4's braking system. Even if the brakes feel fine, brake fluid degrades over time by absorbing moisture.

Brake Fluid Type and Interval:

  • Your 2021 Cadillac CT4 typically uses DOT4 brake fluid. Always double-check your owner's manual or the cap on your brake fluid reservoir to confirm. Using the wrong fluid can cause damage to seals and internal components.
  • GM generally recommends a brake fluid flush every 2 years or 45,000 miles, whichever comes first. At 35,000 miles and being a 2021 model, you're either at or approaching the 2-year mark, making this an ideal time for service.

Causes of Brake Fluid Degradation:

  • Moisture Absorption (Hydroscopic): Brake fluid is hydroscopic, meaning it absorbs moisture from the air over time. Water in the fluid lowers its boiling point, which can lead to brake fade under heavy braking. It also promotes internal corrosion within the brake lines, calipers, and ABS module.
  • Contamination: Small rubber particles from hoses and seals, or metal particles from components, can contaminate the fluid.

Recommended Action Steps:

  1. Inspect Fluid Color: Check the brake fluid in the reservoir. New DOT4 fluid is typically clear or light amber. If it's dark brown or black, it's heavily contaminated and needs immediate flushing.
  2. Professional Flush Recommended: While a simple bleed can be done DIY, a full flush, especially on modern vehicles with ABS, traction control, and stability control systems, often requires a pressure bleeder and sometimes a diagnostic scan tool (to cycle the ABS pump) to ensure all old fluid is removed and no air is trapped.
  3. Use High-Quality Fluid: If you or your shop are performing the flush, ensure a fresh, sealed container of DOT4 fluid is used. Do not use fluid from an opened container that has been sitting for a long time, as it may have already absorbed moisture.

When to See a Shop:

  • Any Brake System Warning Lights: If your ABS, traction control, or brake warning light illuminates, indicating a potential system fault.
  • Spongy or Soft Pedal: This is a classic sign of air in the system or severely degraded fluid.
  • Lack of Proper Tools: If you don't have a pressure bleeder, vacuum bleeder, or a helper for a traditional two-person bleed, taking it to a professional is safer.
  • Unfamiliarity with ABS Bleeding: If your vehicle requires an ABS module bleed procedure (which often needs a scan tool), a professional shop is essential to avoid leaving old fluid or air in the system.
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