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Dorman - First Stop Brake Master Cylinder P/N:M39580
$74.99
Build the hydraulic pressure that operates all four brake circuits with the Dorman - First Stop Brake Master Cylinder M39580. It installs as a direct-fit replacement for the 1985-1990 Buick Electra, 1986-1990 Buick LeSabre, 1986-1990 Cadillac DeVille, 1986-1990 Cadillac Fleetwood, 1985-1990 Oldsmobile 98, 1986-1990 Oldsmobile Custom Cruiser, 1986-1990 Oldsmobile Delta 88, and 1987-1990 Pontiac Bonneville [All engines], precision-engineered to reproduce the original unit's design, function, and performance.
- Aluminum housing: constructed to match the casting material of the original part for similar performance.
- EPDM seals: all rubber components use a high-quality EPDM compound for resistance to glycol-based brake fluid.
- 100% new: made entirely of new materials, not remanufactured, and built to meet SAE International standards.
- Reservoir included: ships with the fluid reservoir; a fluid-level sensor and mounting hardware are not included.
The master cylinder converts brake-pedal force into hydraulic pressure delivered through its four outlets (outlet threads M11 x 1.5 and M16 x 1.5; bore diameter varies by application). Signs this part may need replacing include a slowly sinking or spongy pedal and external fluid seepage at the cylinder body; diagnose the cause before replacing. Country of origin: China.
Interchange: Manufacturer part number M39580.
Frequently Asked Questions
What does this master cylinder do?
It converts brake-pedal force into hydraulic pressure and routes it through four outlets to the brake circuits. Bench-bleed it before installation for proper operation.
Which vehicles does the M39580 fit?
Direct-fit replacement for the 1985-1990 Buick Electra and Oldsmobile 98, 1986-1990 Buick LeSabre, Cadillac DeVille/Fleetwood, Oldsmobile Custom Cruiser/Delta 88, and 1987-1990 Pontiac Bonneville [All engines]. See the Buyer's Guide tab.
Does it include a reservoir, sensor, or mounting hardware?
It ships with the fluid reservoir included. A fluid-level sensor and mounting hardware are not included; consult the service information for the correct fasteners and whether they may be reused.
What is this master cylinder made of?
The cylinder housing is aluminum, constructed to match the casting material of the original part, and all rubber components use a high-quality EPDM compound for resistance to glycol-based brake fluid.
How do I know my master cylinder needs replacing?
A slowly sinking or spongy brake pedal and external fluid seepage at the cylinder body can be signs it may need replacing. Diagnose the cause first, since these symptoms can have other sources.
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Dorman - First Stop Brake Master Cylinder P/N:M39580
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