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Dorman M630021 Brake Master Cylinder
Reliable Brake Master Cylinder for Chevrolet, GMC, Isuzu, and Oldsmobile
The Dorman M630021 brake master cylinder is engineered to restore proper brake hydraulics in select Chevrolet, GMC, Isuzu, and Oldsmobile vehicles. Designed with an aluminum body and a built-in reservoir, this master cylinder supports consistent brake fluid delivery for improved stopping performance.
- Master cylinder bore diameter: 1 inch
- Constructed from durable aluminum material
- Includes reservoir for brake fluid
- Two outlet ports for brake line connections
- Rearward outlet size: 1/2-20 thread
- Secondary outlet thread diameter: 9/16-18
- Package contains the master cylinder only; mounting hardware not included
Technical Details and Compatibility
The Dorman M630021 brake master cylinder is specifically designed for compatibility with Chevrolet Blazer, GMC Jimmy, Isuzu Hombre, Oldsmobile Bravada, Chevrolet S10, and GMC Sonoma models. Its 1-inch bore diameter and aluminum construction provide reliable hydraulic pressure and corrosion resistance. The integrated reservoir simplifies installation and maintenance by ensuring proper brake fluid containment. Featuring two outlets with precise thread sizes (1/2-20 rearward and 9/16-18 secondary), this master cylinder supports secure brake line connections for effective brake system operation.
Common Applications and Problem Resolution
- Restores brake pressure in vehicles experiencing soft or spongy brake pedal feel
- Replaces leaking or damaged master cylinders causing brake fluid loss
- Addresses brake system failure due to internal seal wear or corrosion
- Improves brake response in Chevrolet Blazer, GMC Jimmy, and related models
- Ensures proper brake fluid flow in Isuzu Hombre and Oldsmobile Bravada vehicles
Installation Notes and Tips
Installation of the Dorman M630021 master cylinder requires removal of the old unit and proper connection of brake lines to the two outlet ports. Since mounting hardware is not included, retain or source compatible fasteners for secure mounting. Bleed the brake system thoroughly after installation to remove air and ensure optimal brake performance. Verify thread sizes (1/2-20 rearward and 9/16-18 secondary) match brake line fittings before assembly.
Quality Assurance and Warranty
Dorman manufactures the M630021 brake master cylinder to meet or exceed OEM specifications for fit, form, and function. The aluminum construction offers corrosion resistance and durability under normal operating conditions. While mounting hardware is not included, the product is backed by Dorman's quality standards. Please consult Dorman's warranty policy for specific coverage details.
| Brand | Dorman |
|---|---|
| Part Number | M630021 |
| Master Cylinder Bore Diameter | 1 |
| Master Cylinder Material | Aluminum |
| Mounting Hardware Included | No |
| Number of Outlets | 2 |
| Package Contents | Master Cylinder |
| Rearward Outlet Size | 1/2-20 |
| Reservoir Included | Yes |
| Secondary Outlet Thread Diameter | 9/16-18 |
| Sensor Included | No |
This part fits 14 vehicles. Search below:
| Year | Make | Model | Position | Notes |
|---|---|---|---|---|
| 2000 | Chevrolet | Blazer | N/A | 11th Digit of VIN is 2; Bore: 1 In.; Built at Moraine, Ohio Plant |
| 2000 | Oldsmobile | Bravada | N/A | 11th Digit of VIN is 2; Bore: 1 In.; Built at Moraine, Ohio Plant |
| 1999 | Chevrolet | Blazer | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1999 | Chevrolet | S10 | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1999 | GMC | Jimmy | N/A | |
| 1999 | GMC | Sonoma | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1999 | Isuzu | Hombre | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1999 | Oldsmobile | Bravada | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1998 | Chevrolet | Blazer | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1998 | Chevrolet | S10 | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1998 | GMC | Jimmy | N/A | |
| 1998 | GMC | Sonoma | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1998 | Isuzu | Hombre | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
| 1998 | Oldsmobile | Bravada | N/A | Compatible with 1-inch bore drum brake wheel cylinders. |
* 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.