American Honda Motor Co. has issued a voluntary safety recall for certain Acura ILX sedans due to a defect in the hydraulic braking system. The campaign affects approximately 70,658 vehicles produced between the 2016 and 2020 model years. The National Highway Traffic Safety Administration (NHTSA) has assigned recall number 25V859 to this action.
Highlights
- Vehicle Population: The recall impacts 70,658 Acura ILX vehicles manufactured from 2014 to 2020.
- Defect Cause: Residual plasticizer from the brake reservoir hose causes the master cylinder seal to swell.
- Safety Risk: The defect can reduce brake-pedal firmness and increase stopping distances.
- Remedy: Dealers will replace the master cylinder assembly with a redesigned component.
Technical Defect Analysis
The defect originates from residual plasticizer in the brake reservoir hose, which can leach into the brake fluid. This contamination causes the secondary cup seal within the brake master cylinder to swell and deform.
Engine heat generated during operation further expands the swollen seal. This expansion compromises the component’s sealing ability, allowing brake fluid to bypass the seal.
Honda identified that a short interval between the production of the reservoir hose and vehicle assembly resulted in the elevated residual plasticizer levels.
Component and Supplier Information
The specific component involved is the Master Cylinder Assembly, identified by part number 46100-TV9-A02.
This component is manufactured by the following Tier 1 supplier:
- Supplier Name: Astemo Ueda, Ltd.
- Location: 840 Kokubu Ueda, Ueda Foreign States, 386-0016, Japan
Safety Implications and Warnings
The failure of the master cylinder cup seals can lead to a noticeable reduction in brake-pedal firmness. During slow brake-pedal applications, the hydraulic pressure in the secondary chamber fails to build properly.
This loss of pressure results in reduced braking force. Consequently, the defect increases the vehicle’s stopping distance, raising the risk of a crash or injury.
Incident Data
Honda first received a complaint regarding intermittent loss of brake pedal pressure in December 2015. As of December 5, 2025, the automaker has processed 192 warranty claims related to this issue. There have been no reports of injuries or deaths associated with this recall.
Remedy and Notification Schedule
Authorized Acura dealers will replace the brake master cylinder with an improved part. The remedy component utilizes a redesigned sealing cup made from different materials to ensure appropriate sealing capability.
Dealer notification for this campaign is scheduled to occur on December 12, 2025. Interim notification letters to registered owners are expected to be mailed on February 2, 2026.
Honda has assigned the manufacturer recall number RN5 to this campaign. The affected Acura ILX model is no longer in production.
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