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Dorman M99031 Brake Master Cylinder
Reliable Brake Master Cylinder for Buick, Chevrolet, Oldsmobile, and Pontiac
The Dorman M99031 brake master cylinder is designed to restore proper brake hydraulics in select Buick, Chevrolet, Oldsmobile, and Pontiac vehicles. Engineered with a cast iron body and a 0.938-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 containment
- Two outlet ports with rearward outlet size 1/2-20 and secondary outlet thread diameter 9/16-18
- Compatible with multiple Buick, Chevrolet, Oldsmobile, and Pontiac models
- Mounting hardware not included
Product Details and Specifications
The Dorman M99031 master cylinder features a 0.938-inch bore diameter, which is critical for maintaining proper hydraulic pressure in the brake system. Constructed from cast iron, this master cylinder offers strength and resistance to wear over time. It comes with an integrated reservoir to hold brake fluid, eliminating the need for a separate component. The unit has two outlets: a rearward outlet sized at 1/2-20 and a secondary outlet with a 9/16-18 thread diameter, designed to connect seamlessly with your vehicle's brake lines. Note that mounting hardware is not included and must be sourced separately.
Compatible Vehicles and Applications
This brake master cylinder is compatible with a range of Buick, Chevrolet, Oldsmobile, and Pontiac models, including:
- Buick Century, Regal
- Chevrolet El Camino, Malibu, Monte Carlo
- Oldsmobile Cutlass, Cutlass Calais, Cutlass Cruiser, Cutlass Supreme, Grand LeMans, LeMans
- Pontiac Grand Am, Grand Prix
Use the Dorman M99031 to replace a failing or leaking master cylinder in these vehicles to restore proper brake function.
Common Issues Addressed by This Master Cylinder
- Brake pedal sinking or sponginess due to internal leaks
- Brake fluid leaks from the master cylinder reservoir or outlets
- Reduced braking efficiency or uneven brake pressure
- Brake warning light activation related to hydraulic failure
- Contaminated or damaged master cylinder bore affecting brake performance
Installation Notes and Tips
- Ensure the brake system is properly bled after installation to remove air
- Verify compatibility with your specific vehicle year and model before installation
- Use appropriate brake fluid as specified by the vehicle manufacturer
- Mounting hardware is not included; retain original hardware or purchase separately
- Inspect brake lines and fittings for wear or damage during replacement
Quality Assurance and Warranty
Dorman manufactures the M99031 master cylinder to meet or exceed OEM standards for fit and function. The cast iron construction provides durability and long service life. While specific warranty details may vary, Dorman typically offers a limited warranty covering defects in materials and workmanship. Consult product documentation or Dorman directly for exact warranty terms.
| Brand | Dorman |
|---|---|
| Part Number | M99031 |
| Master Cylinder Bore Diameter | 0.938 |
| Master Cylinder Material | Cast Iron |
| 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 38 vehicles. Search below:
| Year | Make | Model | Submodel | Fuel Type | Position | Notes |
|---|---|---|---|---|---|---|
| 1980 | Buick | Century | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1980 | Buick | Regal | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1980 | Chevrolet | El Camino | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1980 | Chevrolet | Malibu | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1980 | Chevrolet | Monte Carlo | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1980 | Oldsmobile | Cutlass | GAS | N/A | Fits vehicles with a 3/4 inch bore size. | |
| 1980 | Oldsmobile | Cutlass Calais | GAS | N/A | Fits vehicles with a 3/4 inch bore size. | |
| 1980 | Oldsmobile | Cutlass Cruiser | GAS | N/A | Fits vehicles with a 3/4 inch bore size. | |
| 1980 | Oldsmobile | Cutlass Supreme | GAS | N/A | Fits vehicles with a 3/4 inch bore size. | |
| 1980 | Pontiac | Grand Am | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1980 | Pontiac | Grand LeMans | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1980 | Pontiac | Grand Prix | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1980 | Pontiac | LeMans | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Buick | Century | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Buick | Regal | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Chevrolet | El Camino | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Chevrolet | Malibu | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Chevrolet | Monte Carlo | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Oldsmobile | Cutlass | GAS | N/A | Fits vehicles with a 3/4 inch bore size. | |
| 1979 | Oldsmobile | Cutlass Calais | GAS | N/A | Fits vehicles with a 3/4 inch bore size. | |
| 1979 | Oldsmobile | Cutlass Supreme | GAS | N/A | Fits vehicles with a 3/4 inch bore size. | |
| 1979 | Pontiac | Grand Am | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Pontiac | Grand LeMans | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Pontiac | Grand Prix | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1979 | Pontiac | LeMans | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Buick | Century | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Buick | Regal | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Chevrolet | El Camino | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Chevrolet | Malibu | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Chevrolet | Monte Carlo | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Oldsmobile | Cutlass | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Oldsmobile | Cutlass Calais | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Oldsmobile | Cutlass Supreme | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Pontiac | Grand Am | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Pontiac | Grand LeMans | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Pontiac | Grand Prix | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1978 | Pontiac | LeMans | N/A | Fits vehicles with a 3/4 inch bore size. | ||
| 1977 | Oldsmobile | Cutlass | Vista Cruiser | N/A | Fits vehicles with a 3/4 inch 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.