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Dorman M630405 Brake Master Cylinder
Brake Master Cylinder for 2008 Cadillac CTS and STS
Dorman M630405 is a brake master cylinder built for specific 2008 Cadillac applications, including the CTS and STS. It is engineered to match the original unit’s design, function, and performance, with new materials selected for durable brake system service.
Key Features
- Direct replacement brake master cylinder for select 2008 Cadillac CTS and 2008 Cadillac STS applications
- 1.031-inch bore diameter for the listed fitments
- Aluminum master cylinder construction
- Reservoir included
- Sensor included
- Two outlets with M13 x 1.5 thread size
- Part number M630405
Detailed Description
This Dorman brake master cylinder is designed for vehicles that require a 1.0313-inch bore size, including the 2008 Cadillac CTS and 2008 Cadillac STS with Active Steering Control. The aluminum body and included reservoir help support a clean OE-style replacement for the original hydraulic brake assembly. Dorman M630405 is also cross-referenced to Monroe Shocks & Struts 172286 for the same application.
Use this brake master cylinder when replacing a worn, leaking, or internally bypassing unit on the 2008 Cadillac CTS or 2008 Cadillac STS. The sensor and dual outlet configuration support proper integration with the vehicle’s brake hydraulic system, while the matched bore size helps maintain original pedal and braking characteristics.
Common Problems This Part Can Address
- Brake pedal sinking or gradual pedal drop
- External brake fluid leakage at the master cylinder
- Internal bypass causing inconsistent hydraulic pressure
- Brake warning light concerns related to master cylinder sensor issues
- Loss of braking performance from a worn hydraulic unit
Installation Notes and Tips
Verify bore size, outlet thread size, and vehicle configuration before installation. This part does not include mounting hardware. After installation, bleed the brake system thoroughly and confirm there are no fluid leaks at the outlets, reservoir, or line connections. For the listed 2008 Cadillac STS application, confirm Active Steering Control and bore specification match the vehicle.
Quality Assurance
Dorman manufactures this replacement master cylinder using new, high-quality materials and designs it to match the original part’s function and performance on the specified vehicles. Part number M630405 is built for direct-fit service on the listed Cadillac applications.
| Brand | Dorman |
| Part Number | M630405 |
| Mounting Hardware Included | No |
| Master Cylinder Bore Diameter | 1.031 |
| Master Cylinder Material | Aluminum |
| Reservoir Included | Yes |
| Sensor Included | Yes |
| Number of Outlets | 2 |
| Package Contents | Master cylinder |
| Rearward Outlet Size | M13 x 1.5 |
| Secondary Outlet Thread Diameter | M13 x 1.5 |
| Thread Pitch | 1.5 |
This part fits 2 vehicles. Search below:
| Year | Make | Model | Position | Notes |
|---|---|---|---|---|
| 2008 | Cadillac | CTS | N/A | Brake Master Cylinder bore size is 1.0313 inches. |
| 2008 | Cadillac | STS | N/A | Bore: 1.0313 In.; w/Active Steering Control |
* Always verify fitment with your vehicle's VIN if unsure. Submodel & trim restrictions may apply.
This part directly replaces or is cross-referenced with the following part numbers:
Cross-reference numbers are provided for identification purposes only. Always confirm fitment before ordering.