Generate the hydraulic pressure your brakes depend on with the Dorman - First Stop Brake Master Cylinder M104458. When you press the pedal, the master cylinder pressurizes the brake fluid and sends it to the wheel circuits. This unit installs as a direct-fit replacement for the listed 1981-1992 GM applications, engineered to reproduce the original master cylinder's operation and feel. It ships as a 100% new assembly (not remanufactured) with the fluid reservoir already included.
- 100% new: built entirely from new materials rather than rebuilt, for consistent quality.
- Aluminum housing: the cylinder housing is constructed to match the casting material of the original part for similar performance.
- EPDM seals: rubber components use a high-quality EPDM compound that resists glycol-based brake fluid.
- Built to spec: made to meet rigorous SAE International standards; features two outlets with a 1/2-20 rearward outlet size.
Reservoir included; no sensor and no mounting hardware are supplied — consult the vehicle service information for the correct fasteners and whether they may be reused. If a failed master cylinder is the cause of a sinking pedal or fluid loss, this replaces it; diagnose the cause before replacing.
Fitment (all engines): Buick Electra 1981-1985 & 1987-1989; Buick Estate Wagon 1981-1983; Buick LeSabre 1981-1985 & 1987-1990; Buick Regal 1982-1983; Cadillac Brougham 1987-1992; Cadillac DeVille 1981-1984; Cadillac Fleetwood 1981-1989; Chevrolet Camaro 1981; Chevrolet Caprice 1981-1990; Chevrolet Impala 1981-1985; Oldsmobile 98 1981-1984; Oldsmobile Custom Cruiser 1981-1990; Oldsmobile Delta 88 1981-1985; Pontiac Bonneville 1981; Pontiac Catalina 1981; Pontiac Firebird 1981; Pontiac Parisienne 1983-1986; Pontiac Safari 1987-1989. See the Buyer's Guide tab for the full list.
Interchange: Manufacturer part number M104458.
Frequently Asked Questions
What does the master cylinder do?
It converts brake-pedal force into hydraulic pressure, pushing brake fluid through the outlets to the wheel circuits. This M104458 unit replaces the original master cylinder on the listed applications.
Does it come with a reservoir?
Yes, the fluid reservoir is included. A sensor is not included with this master cylinder.
Is mounting hardware included?
No. Consult the vehicle service information for the correct fasteners and whether they may be reused.
What is this master cylinder made of?
The housing is aluminum, constructed to match the original part's casting material, and its rubber components use an EPDM compound that resists glycol-based brake fluid.
Which vehicles does it fit?
It's a direct-fit replacement for many 1981-1992 Buick, Cadillac, Chevrolet, Oldsmobile, and Pontiac models. Check the Buyer's Guide tab to confirm your year and model.
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