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Dorman - First Stop Brake Master Cylinder P/N:M39661
$159.99
Turn brake-pedal effort into the hydraulic pressure that operates the braking system with the Dorman – First Stop Brake Master Cylinder M39661. It drops in as a direct-fit replacement engineered to match the design, function, and performance of the original master cylinder on the listed classic Mercedes-Benz models — including the 1977-1985 300D, 1975-1980 450SLC and 1981-1985 380SL — so it operates like the factory unit on those applications.
- Precise replacement: the cylinder housing is built to match the casting material of the original part for similar performance.
- Durable design: 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.
- Strict specifications: made to meet rigorous SAE International standards.
The cast iron housing carries three outlets, with M10 x 1.0 rearward and secondary outlet threads. A reservoir, mounting hardware, and sensor are not included — transfer or source these as directed by the vehicle service procedure. If a failing master cylinder is the cause of a sinking or spongy pedal or fluid loss, this replaces it; diagnose the cause first. Country of origin: Italy.
Fitment: 1975-1980 450SLC · 1977-1985 300D · 1977-1981 280E · 1977-1979 450SEL · 1978-1983 240D · 1978-1981 280CE · 1978-1981 300CD · 1980-1985 300TD · 1980 450SL · 1981-1985 380SL · 1981-1983 380SEL · 1981 380SLC · 1982-1983 380SEC · 1984-1985 380SE (all [All] engines; see the Buyer's Guide tab for the full list).
Interchange: Manufacturer part number M39661.
Frequently Asked Questions
What does this brake master cylinder do?
It converts the force you apply at the brake pedal into hydraulic pressure and distributes it through its outlets to the braking system.
Which vehicles does the M39661 fit?
It is a direct-fit replacement for many 1975-1985 Mercedes-Benz models, such as the 240D, 280CE, 280E, 300CD, 300D, 300TD, 380SE, 380SL and 450SLC. See the Buyer's Guide tab for the full list.
Does it come with a reservoir, sensor, or mounting hardware?
No. The reservoir, sensor, and mounting hardware are not included; transfer or source them as directed by the vehicle service procedure.
What is the M39661 made of?
It has a cast iron housing built to match the original's casting material, with EPDM rubber components for resistance to glycol-based brake fluid, and it is 100% new rather than remanufactured.
What are signs the master cylinder may need replacing?
A sinking or spongy brake pedal or loss of brake fluid can be signs. These symptoms have other causes, so diagnose the system before replacing this part.
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Dorman - First Stop Brake Master Cylinder P/N:M39661
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