Dorman - First Stop Brake Master Cylinder
Dorman - First Stop Brake Master Cylinder - view 2
Dorman - First Stop Brake Master Cylinder - view 3
Dorman - First Stop Brake Master Cylinder - view 4
Dorman - First Stop Brake Master Cylinder
Dorman - First Stop Brake Master Cylinder - view 2
Dorman - First Stop Brake Master Cylinder - view 3
Dorman - First Stop Brake Master Cylinder - view 4

Dorman - First Stop Brake Master Cylinder P/N:M630838

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$204.99
MPN: M630838
UPC: 885484270442
Item Package Quantity: 1
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Dorman - First Stop Brake Master Cylinder P/N:M630838
Dorman - First Stop Brake Master Cylinder P/N:M630838
$204.99

Restore firm, consistent brake-pedal feel with the Dorman - First Stop Brake Master Cylinder (M630838), the component that converts brake-pedal force into the hydraulic pressure that feeds the brake circuits. Engineered to reproduce the form and performance of the factory unit, it installs on the 2011 BMW 1 Series M [All] and the 2008-2012 BMW M3 [All].

  • Aluminum housing: constructed to match the casting material of the original part for similar performance.
  • Durable EPDM seals: all rubber components use a high-quality EPDM compound for resistance to glycol-based brake fluid.
  • 100% new: built entirely from new materials, not remanufactured.
  • Strict specifications: made to meet rigorous SAE International standards.

This unit has a 0.875 in bore diameter and two outlets, with an M12 x 1.0 rearward/secondary outlet and a 1 mm primary outlet thread pitch. The reservoir, sensor, and mounting hardware are not included. Country of origin: Taiwan. If a failing master cylinder is the cause of a sinking or soft pedal, this replaces it; diagnose the cause before ordering.

Interchange: 100-2817 · 1002817 · 34312283533 · 11-3850 · 113850 · 130.34203 · 355-31060 · 35531060 · MC391423 · R135637
Manufacturer part number M630838 · Part Eazy SKU M630838

This part cross-references / interchanges with the following part numbers:

100-2817, 34312283533, 11-3850, 130.34203, 355-31060, MC391423, R135637

Frequently Asked Questions

What does this master cylinder do?

It converts the force from your brake pedal into hydraulic pressure, sending fluid through its two outlets to operate the vehicle's brake circuits.

Which vehicles does the M630838 fit?

It's a direct-fit replacement for the 2011 BMW 1 Series M [All] and the 2008-2012 BMW M3 [All]. Check the Buyer's Guide tab to confirm fitment for your vehicle.

Does it include a reservoir, sensor, or mounting hardware?

No. The reservoir, sensor, and mounting hardware are not included, so plan to transfer or source those items as directed by the service procedure.

What are signs my master cylinder may need replacing?

Signs that may point to the master cylinder include a pedal that slowly sinks to the floor, a soft or spongy pedal, or internal fluid loss. Diagnose the cause before replacing.

What is it made of and where is it made?

The cylinder housing is aluminum, constructed to match the casting material of the original part, with EPDM rubber components. Country of origin: Taiwan.

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