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Dorman M39630 Brake Master Cylinder
Reliable Brake Master Cylinder for Chevrolet and GMC Vehicles
The Dorman M39630 Brake Master Cylinder is engineered to restore proper brake hydraulics in select Chevrolet and GMC models. Designed with durable aluminum construction and a built-in reservoir, this master cylinder ensures consistent brake fluid delivery for safe stopping performance.
- Aluminum master cylinder material for corrosion resistance and durability
- Includes reservoir for brake fluid storage
- Dual outlet design with 1/2-20 rearward outlet and 9/16-18 secondary outlet thread diameters
- Master cylinder bore diameter of 1-1/4 inch and 40mm for precise hydraulic pressure
- Compatible with Chevrolet G30, GMC P20, P30, P2500, and P3500 models
- Part number M39630 for accurate replacement
Product Details and Specifications
This Dorman brake master cylinder (part number M39630) is constructed from aluminum to provide long-lasting resistance to wear and corrosion. It includes an integrated reservoir to hold brake fluid, eliminating the need for a separate component. The master cylinder features two outlets: a rearward outlet sized 1/2-20 and a secondary outlet with a 9/16-18 thread diameter, supporting proper brake line connections. The bore diameter measures 1-1/4 inch (40mm), which is critical for maintaining the correct hydraulic pressure within the brake system. This part is designed specifically for use in Chevrolet G30 and GMC P20, P30, P2500, and P3500 vehicles, ensuring compatibility and reliable performance.
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 worn internal seals or corrosion
- Improves brake response in Chevrolet G30 and GMC P-series vans and trucks
- Eliminates inconsistent braking caused by faulty master cylinder components
Installation Notes and Tips
Installation of the Dorman M39630 master cylinder requires proper brake system bleeding to remove air and ensure optimal hydraulic function. Mounting hardware is not included, so existing hardware should be inspected and replaced if necessary. Verify thread sizes on brake lines match the 1/2-20 rearward outlet and 9/16-18 secondary outlet to ensure proper fitment. It is recommended to inspect related brake components such as brake lines and wheel cylinders during installation for comprehensive brake system maintenance.
Quality Assurance and Warranty Information
Dorman manufactures this brake master cylinder to meet or exceed OEM specifications for fit, form, and function. The aluminum construction and integrated reservoir contribute to the part's durability and reliability. While specific warranty details are not provided here, Dorman typically offers limited warranties on their brake hydraulics products. Consult product packaging or Dorman's official resources for exact warranty terms.
| Brand | Dorman |
|---|---|
| Part Number | M39630 |
| Master Cylinder Bore Diameter | 1-1/4 in & 40mm |
| 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 58 vehicles. Search below:
| Year | Make | Model | Fuel Type | Position | Notes |
|---|---|---|---|---|---|
| 1996 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1996 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1995 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1995 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1994 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1994 | Chevrolet | P30 | N/A | Bore sizes of 31.75 mm and 40 mm, compatible with Forward Control and Motorhome Chassis. | |
| 1994 | Chevrolet | P30 | N/A | Bore: 31.75 mm and 40 mm; 8,400 Lb. GVW; wo/Motorhome Chassis | |
| 1994 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1994 | GMC | P3500 | N/A | Bore sizes of 31.75 mm and 40 mm, compatible with Forward Control and Motorhome Chassis. | |
| 1994 | GMC | P3500 | N/A | Bore: 31.75 mm and 40 mm; 8,400 Lb. GVW; wo/Motorhome Chassis | |
| 1993 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1993 | Chevrolet | P30 | N/A | Bore sizes of 31.75 mm and 40 mm, compatible with Forward Control and Motorhome Chassis. | |
| 1993 | Chevrolet | P30 | N/A | Bore: 31.75 mm and 40 mm; 8,400 Lb. GVW; wo/Motorhome Chassis | |
| 1993 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1993 | GMC | P3500 | N/A | Bore sizes of 31.75 mm and 40 mm, compatible with Forward Control and Motorhome Chassis. | |
| 1993 | GMC | P3500 | N/A | Bore: 31.75 mm and 40 mm; 8,400 Lb. GVW; wo/Motorhome Chassis | |
| 1992 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1992 | Chevrolet | P30 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1992 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1992 | GMC | P3500 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1991 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1991 | Chevrolet | P30 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1991 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1991 | GMC | P3500 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1990 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1990 | Chevrolet | P30 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1990 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1990 | GMC | P3500 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1989 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1989 | Chevrolet | P20 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1989 | Chevrolet | P30 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1989 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1989 | GMC | P2500 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1989 | GMC | P3500 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1988 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1988 | Chevrolet | P20 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1988 | Chevrolet | P30 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1988 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1988 | GMC | P2500 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1988 | GMC | P3500 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1987 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1987 | Chevrolet | P20 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1987 | Chevrolet | P30 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1987 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1987 | GMC | P2500 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1987 | GMC | P3500 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1986 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1986 | Chevrolet | P20 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1986 | Chevrolet | P30 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1986 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1986 | GMC | P2500 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1986 | GMC | P3500 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1985 | Chevrolet | G30 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1985 | Chevrolet | P20 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1985 | Chevrolet | P30 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
| 1985 | GMC | G3500 | GAS | N/A | Bore sizes of 31.75mm and 40mm compatible with vehicles with Single Rear Wheel (SRW) configuration. |
| 1985 | GMC | P2500 | GAS | N/A | Brake Master Cylinder with bore sizes of 31.75mm and 40mm, compatible with 13 inch x 2.50 inch brakes. |
| 1985 | GMC | P3500 | GAS | N/A | Bore: 31.75 mm and 40 mm; 8,200 Lb. GVW; wo/Motorhome Chassis |
* 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.