Owners of certain 2016–2020 Acura ILX vehicles may be experiencing an unsettling brake issue that develops quietly over time. While it does not always appear suddenly or trigger warning lights, the condition can reduce brake effectiveness during everyday driving—particularly during gentle or slow brake applications. For drivers, any issue involving braking deserves close attention.
What Is the Brake Problem?
The issue centers on the brake master cylinder, a critical component responsible for converting pedal pressure into braking force. In the affected vehicles, a material used in the brake fluid reservoir hose can release excess plasticizer into the brake fluid.
Over time, this contamination causes a seal inside the master cylinder (known as the secondary cup seal) to swell and deform. Heat from the engine can make the problem worse.
When this happens:
- Brake fluid can bypass the seal instead of building proper pressure
- The brake pedal may feel softer or less firm
- Stopping distances may increase, especially during light or gradual braking
In real-world driving, this means the vehicle may not slow down as expected—raising the risk of a crash or injury.
Why Did This Happen?
The root cause traces back to manufacturing timing. The brake reservoir hose was installed too soon after production, before excess plasticizer had time to dissipate. That plasticizer leached into the brake fluid, which was then absorbed by the master cylinder seal.
As the seal absorbed the contaminant and expanded:
- Its shape and flexibility changed
- It could no longer maintain a proper seal under certain braking conditions
- Brake fluid was allowed to leak back into the reservoir
The result is reduced hydraulic pressure when the driver presses the brake pedal slowly.
A Long Investigation Timeline
Honda and Acura engineers spent nearly a decade analyzing this issue:
- 2015–2021: Initial complaints of intermittent brake pedal pressure loss
- 2022–2024: Extensive testing confirmed chemical contamination and seal swelling
- 2025: A clear link was found between hose storage timing, material curing, and seal deformation
By late 2025, the manufacturer determined that this condition posed a motor vehicle safety defect and initiated corrective action.
As of December 2025, there were 192 warranty claims associated with the issue. Fortunately, no injuries or fatalities have been reported.
What Is Being Done to Fix It?
Owners of affected vehicles will be notified by mail and instructed to visit an authorized Acura dealer. The repair involves:
- Replacing the brake master cylinder
- Installing an improved sealing cup made from a different material
- Restoring proper brake fluid sealing and pedal feel
This updated design is intended to eliminate the contamination-related swelling entirely.
Why This Matters for Lemon Law Claims
Even if a manufacturer offers a fix, brake-related defects can still be relevant under Lemon Law statutes, especially if:
- The problem existed during the warranty period.
- You experienced repeated brake complaints or repairs.
- The issue affected vehicle safety, drivability, or value.
