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Dorman M101258 Brake Master Cylinder
Reliable Brake Master Cylinder for Buick, Cadillac, and Pontiac
The Dorman M101258 brake master cylinder is engineered to restore proper brake hydraulics in select Buick, Cadillac, and Pontiac models. Designed with a cast iron body and a 1.125-inch bore diameter, this master cylinder ensures consistent brake fluid pressure for safe and effective braking performance.
- Cast iron master cylinder material for durability
- Includes reservoir for brake fluid
- 1.125-inch bore diameter for precise hydraulic control
- Two outlets with secondary outlet thread diameter of 0.5 inches
- Rearward outlet size of 9/16-18 for secure connections
- Compatible with Buick DeVille, Cadillac Fleetwood, Seville, and more
- Part number M101258 for accurate replacement
Detailed Product Description
This Dorman brake master cylinder (part number M101258) is designed specifically for brake hydraulics systems in various Buick, Cadillac, and Pontiac vehicles, including the DeVille, Firebird, Fleetwood, LeSabre, Riviera, and Seville models. Constructed from cast iron, the master cylinder offers strength and resistance to wear, ensuring long-lasting performance. The included reservoir simplifies brake fluid management, while the 1.125-inch bore diameter provides the correct hydraulic pressure needed for effective braking. Featuring two outlets, including a rearward outlet sized 9/16-18 and a secondary outlet with a 0.5-inch thread diameter, this master cylinder supports proper brake line connections without the need for additional sensors or mounting hardware.
Common Applications and Issues Addressed
- Restores brake fluid pressure in hydraulic brake systems
- Replaces worn or leaking master cylinders causing brake failure
- Eliminates spongy or unresponsive brake pedal feel
- Fixes brake fluid leaks from the master cylinder reservoir
- Ensures proper brake function in Buick DeVille, Cadillac Seville, and Pontiac Firebird models
Installation Notes and Tips
- Ensure compatibility with your vehicle’s make and model before installation
- Bleed the brake system thoroughly after installation to remove air
- Use recommended brake fluid type for your vehicle
- Check all brake line connections for leaks after installation
- Professional installation is advised for safety and performance
Quality Assurance and Warranty
Dorman manufactures this brake master cylinder to meet or exceed OEM specifications for fit and function. While mounting hardware is not included, the part is designed for direct replacement in compatible Buick, Cadillac, and Pontiac models. Please consult Dorman’s warranty policy for coverage details on part number M101258.
| Brand | Dorman |
| Part Number | M101258 |
| Mounting Hardware Included | No |
| Master Cylinder Bore Diameter | 1.125 |
| Master Cylinder Material | Cast iron |
| Reservoir Included | Yes |
| Secondary Outlet Thread Diameter | 0.5 |
| Sensor Included | No |
| Number of Outlets | 2 |
| Package Contents | Master cylinder |
| Rearward Outlet Size | 9/16-18 |
This part fits 18 vehicles. Search below:
| Year | Make | Model | Position | Notes |
|---|---|---|---|---|
| 1980 | Buick | LeSabre | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1980 | Pontiac | Firebird | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | Buick | LeSabre | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | Cadillac | DeVille | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | Cadillac | Fleetwood | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | Cadillac | Seville | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | Pontiac | Firebird | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1978 | Buick | LeSabre | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1978 | Buick | Riviera | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1978 | Cadillac | DeVille | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1978 | Cadillac | Fleetwood | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1978 | Cadillac | Seville | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1977 | Buick | LeSabre | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1977 | Buick | Riviera | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1977 | Cadillac | DeVille | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1977 | Cadillac | Fleetwood | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1977 | Cadillac | Seville | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1976 | Cadillac | Seville | N/A | Compatible with drum brake systems with a 1.125" bore size. |
* 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.