The Dorman - First Stop Brake Master Cylinder M390320 converts the force from your brake pedal into the hydraulic pressure that operates the vehicle's brakes. It installs as a direct-fit replacement for the listed applications, including the 1995-1997 Chevrolet Blazer, 1982-1997 Chevrolet S10, 1983-1994 Chevrolet S10 Blazer, 1991-1997 GMC Sonoma and 1996-1997 Isuzu Hombre — see the Buyer's Guide tab for the full list.
- Aluminum housing: the cylinder housing is built to match the casting material of the original part for similar performance.
- EPDM rubber components: made from a high-quality EPDM compound for resistance to glycol-based brake fluid.
- 100% new: made entirely of new materials, not remanufactured.
- Built to spec: made to meet rigorous SAE International standards.
This unit has two outlets with a 1/2-20 rearward outlet size and includes the reservoir. Mounting hardware is not included and no sensor is supplied; consult the vehicle service information for the correct fasteners and whether they may be reused. Signs the original master cylinder may need replacing include a spongy brake pedal, a pedal that slowly sinks under steady foot pressure, or brake fluid leaking at the cylinder — diagnose the cause before replacing. Country of origin: China. Manufacturer part number M390320.
Frequently Asked Questions
What does this brake master cylinder do?
It converts the force from your brake pedal into the hydraulic pressure that operates the brakes. If a failed master cylinder is the cause of your braking problem, this replaces it.
Does it include a reservoir?
Yes. Per the catalog, the reservoir is included. No sensor is supplied and mounting hardware is not included.
What material is the housing?
The cylinder housing is aluminum, built to match the casting material of the original part for similar performance. All rubber components use an EPDM compound resistant to glycol-based brake fluid.
What vehicles does the M390320 fit?
It's a direct-fit replacement for applications such as the 1995-1997 Chevrolet Blazer, 1982-1997 Chevrolet S10, 1991-1997 GMC Sonoma and 1996-1997 Isuzu Hombre. See the Buyer's Guide tab for the full list.
What are signs my master cylinder may need replacing?
A spongy pedal, a pedal that slowly sinks under steady pressure, or brake fluid leaking at the cylinder can be signs. These have other causes too, so diagnose before replacing.