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Dorman M39077 Brake Master Cylinder
Reliable Brake Master Cylinder for Chevrolet and GMC Vans
The Dorman M39077 brake master cylinder is engineered to restore proper brake hydraulics in Chevrolet and GMC vans, including G10, G20, P10, and P1500 models. Designed with a cast iron body and a 1.125-inch bore diameter, this master cylinder ensures consistent brake fluid pressure for safe stopping performance.
- Master cylinder bore diameter: 1.125 inches for precise hydraulic control
- Durable cast iron construction for long-lasting service
- Includes reservoir for brake fluid storage
- Two outlet ports with rearward outlet size of 9/16-18 and secondary outlet thread diameter of 0.5 inches
- Compatible with Chevrolet G10, G20, P10, and GMC P1500 models
- Part number M39077 for accurate replacement
Product Details and Specifications
This Dorman brake master cylinder features a cast iron material that provides strength and resistance to wear under demanding braking conditions. The 1.125-inch bore diameter is designed to match the hydraulic requirements of the specified Chevrolet and GMC vans, ensuring proper brake fluid displacement. The included reservoir allows for adequate brake fluid storage, while the two outlet ports facilitate fluid distribution to the brake lines. The rearward outlet size measures 9/16-18, and the secondary outlet thread diameter is 0.5 inches, matching OEM specifications for a direct fit replacement. Note that mounting hardware is not included with this part.
Compatible Vehicles and Applications
This brake master cylinder is compatible with the following vehicles:
- Chevrolet G10
- Chevrolet G20
- Chevrolet P10
- GMC P1500
It is designed to replace worn or failing master cylinders in these models, restoring proper brake system function.
Common Issues Addressed by This Master Cylinder
- Spongy or unresponsive brake pedal
- Brake fluid leaks from the master cylinder or reservoir
- Reduced braking efficiency or uneven brake pressure
- Brake warning light activation due to hydraulic failure
- Contaminated or deteriorated internal seals causing brake failure
Installation Notes and Tips
When installing the Dorman M39077 brake master cylinder, ensure the brake system is properly bled to remove air and maintain hydraulic integrity. Verify that the reservoir is filled with the correct brake fluid type recommended for your vehicle. Since mounting hardware is not included, retain or source the necessary bolts and fittings from your original assembly or a trusted supplier. Proper torque specifications should be followed to avoid leaks or damage.
Quality Assurance and Warranty
Dorman manufactures this brake master cylinder to meet or exceed OEM standards for fit, form, and function. The cast iron construction and precise bore diameter contribute to reliable brake system performance. While specific warranty details are not provided here, Dorman typically offers limited warranties on their brake hydraulic components to ensure customer confidence and product durability.
| Brand | Dorman |
| Part Number | M39077 |
| 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 27 vehicles. Search below:
| Year | Make | Model | Position | Notes |
|---|---|---|---|---|
| 1980 | Chevrolet | G10 | N/A | 11.15 In. x 2.75 In. Rear Brakes; Bore: 1.125 In. |
| 1980 | Chevrolet | G20 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1980 | Chevrolet | P10 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1980 | GMC | G1500 | N/A | 11.15 In. x 2.75 In. Rear Brakes; Bore: 1.125 In. |
| 1980 | GMC | G2500 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1980 | GMC | P1500 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | Chevrolet | G10 | N/A | 11.15 In. x 2.75 In. Rear Brakes; Bore: 1.125 In. |
| 1979 | Chevrolet | G20 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | Chevrolet | P10 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | GMC | G1500 | N/A | 11.15 In. x 2.75 In. Rear Brakes; Bore: 1.125 In. |
| 1979 | GMC | G2500 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1979 | GMC | P1500 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1978 | Chevrolet | G10 | N/A | Drum Brake Shoe Hold Down Kit, 11.15 In. x 2.75 In. |
| 1978 | Chevrolet | G20 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1978 | Chevrolet | P10 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1978 | GMC | G15 | N/A | Drum Brake Shoe Hold Down Kit, 11.15 In. x 2.75 In. |
| 1978 | GMC | G25 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1977 | Chevrolet | G20 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1977 | Chevrolet | P10 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1977 | GMC | G25 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1976 | Chevrolet | G20 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1976 | Chevrolet | P10 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1976 | GMC | G25 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1975 | Chevrolet | G20 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1975 | Chevrolet | P10 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1975 | GMC | G25 | N/A | Compatible with drum brake systems with a 1.125" bore size. |
| 1974 | GMC | G25/G2500 Van | N/A | 1.125" bore size compatible with power brakes. |
* 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.