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<h2>What is a car brake master cylinder and what does it do?</h2>A car brake&nbsp;master cylinder plays an important role in the overall balance of the braking system. It is designed to provide equal pressure to all four wheels, which helps ensure that the vehicle stops in a straight line and doesn't pull to one side or the other. It is a hydraulic pump that converts the force applied to the brake pedal by the driver into hydraulic pressure.<h2>Brake master cylinder functions brake master cylinder functions</h2>The main function of the brake master cylinder is to convert the force applied on the brake pedal into hydraulic pressure that is used to actuate the brakes.When the brake pedal is depressed, it pushes a piston inside the master cylinder which in turn pressurizes the brake fluid in the cylinder. This pressure is then transmitted through the brake lines to the individual brake calipers or wheel cylinders, which then apply the brake pads or shoes to the rotors or drums respectively.<h2>Brake master cylinder diagram</h2>The master cylinder also has two fluid chambers, one for the front brakes and one for the rear brakes, to ensure that the brakes operate independently in case of a leak or failure. It also has a reservoir that holds extra brake fluid and allows for topping up the fluid as needed.<img src="https://media.cdn.a-premium.com/2022/item/image/e3c8d30a027b4060a0e2728defc4deb2.gif" alt="brake master cylinder diagram" width="1000" height="375" />Master brake cylinder failure symptomsA failing master brake cylinder can cause a range of symptoms that affect the braking performance of a vehicle. So if you notice the following signs, you may need a new master brake cylinder:<ul><li>Brake pedal goes to the floor: If the brake pedal goes all the way to the floor with little resistance, it may indicate a problem with the master brake cylinder. This can be caused by a loss of hydraulic pressure or a problem with the seals inside the master cylinder.</li><li>Brake pedal feels hard: On the other hand, a brake pedal that feels unusually hard or difficult to press down can also indicate a problem with the master brake cylinder. This can be caused by a restriction in the brake lines or a problem with the master cylinder's internal components.</li><li>Brakes are grabbing or dragging: A failing master brake cylinder can cause the brakes to grab or drag, even when the pedal is not pressed. This can result in reduced fuel economy and increased wear on the brake components.</li><li>Noisy brakes: A faulty master brake cylinder can cause the brakes to make unusual noises, such as squeaking, squealing, or grinding. This can indicate that the brake pads or rotors are worn, or that there is a problem with the brake calipers.</li><li>A brake warning light is on: A failing master brake cylinder can cause the brake warning light to come on. This can indicate a problem with the brake system, such as a leak or a loss of hydraulic pressure.</li></ul><h2>Brake master cylinder replacement steps</h2>Before replacing the brake master cylinder, you need to gather all the necessary tools and equipment. You will need a set of wrenches, pliers, a brake bleeding kit, a container to catch brake fluid, and a new brake master cylinder. After that, follow the steps:<ol><li>Disconnect the brake lines and wiring harness from the old master cylinder.</li><li>Remove the old master cylinder by unscrewing the bolts that secure it to the brake booster.</li><li>Install the new master cylinder onto the brake booster and tighten the bolts.</li><li>Reconnect the brake lines and wiring harness to the new master cylinder.</li><li>Use a brake bleeding kit to bleed the brake lines and remove any air bubbles from the system.</li><li>Test the brake pedal to ensure that it feels firm and responsive.</li><li>Adjust the pushrod that connects the brake booster to the master cylinder, if necessary.</li><li>Check the brake fluid level in the reservoir and top it off if necessary, and you&rsquo;re recommended to use the type of brake fluid recommended by the vehicle manufacturer.</li></ol>

Brake Master Cylinder

Air Cleaner

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Air Filter Box

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Air Flow Sensor

Air Intake Duct

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Air Intake Hose

Air Intake Manifold Actuator Control Solenoid

Air Intake Manifold Flap Adjuster

Air Intake Manifold Runner Control Sensor

Air Intake Resonator

Electric Vacuum Pump

Engine Air Duct Assembly

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Engine Air Filter

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Intake Manifold

Intake Manifold Flap Actuator

Intake Manifold Repair Bracket

Intake Manifold Runner Control Valve

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Intercooler

Intercooler Hose

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Oxygen Sensor

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Pressure Sensor

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Supercharger Pulley Drive Unit

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Supercharger Snout Rebuild Kit

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Throttle Body

Throttle Cable

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Throttle Position Sensor

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Turbocharger

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Turbocharger Gasket Kit

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Turbocharger Oil Line

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Vacuum Pump

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Air Filters & Intake Systems

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Camshaft Adjuster

Camshaft Adjuster Cover

Camshaft Kit

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Camshaft Timing Gear

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Camshafts

Chain Tensioner Adjuster

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Cylinder Head

Cylinder Head Assembly

Eccentric Shaft Actuator

Engine Timing Belt

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Engine Valve Cover

Engine Valve Cover Gasket

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Harmonic Balancer

Rocker Arm

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Rocker Arm Shaft Lifter Assembly

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Timing Belt Kit

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Timing Chain Gear

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Timing Chain Kit

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Timing Cover

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Timing-Control Valve Solenoid

Valve Cover Gasket

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Valve Lifter Guides

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Valve Lifters Tappet

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Cams, Timing & Valvetrain

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Belt Tensioner

Coolant Level Sensor

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Crank Installer Tool

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Crankcase Breather Hose

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Crankcase Breather Valve

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Crankshaft Position Sensor

Crankshaft Pulley

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Engine Oil Dipstick

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Engine Oil Dipstick Tube

Engine Oil Filter

Engine Oil Pan Gasket

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Flywheel

Harmonic Balancer Crankshaft Hub

Knock Sensor

Oil Baffle

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Oil Cooler

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Oil Cooler Line

Oil Drip Pan

Oil Filler Cap

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Oil Filter

Oil Filter Base

Oil Filter Cover

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Oil Filter Housing

Oil Filter Housing Cover

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Oil Level Sensor

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Oil Pan

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Oil Pump

Oil Pump Drive Gear Shaft

Oil Pump Pickup Tube

Oil Separator

Serpentine Belt

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Cranks, Pistons, Oil & Components

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Camshaft Position Sensor

Camshaft Position Sensor & Magnet Kit

Connector Plug

Distributor Cap

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Electronic Ignition System

Engine Valve Covers & Ignition Coils Kits

Glow Plug

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Glow Plug Relay Module

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Ignition Coil

Ignition Coils & Spark Plugs & Wires Kits

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Ignition Coils & Spark Plugs Kits

Ignition Coils & Wires Kits

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Ignition Distributor

Ignition Lock Cylinder

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Ignition Starter Switch

Ignition Switch Actuator

Kill Switch

Knock Detonation Sensor

Relay

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Spark Plug

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Spark Plug Wire

Electronic Control Modules, Ignition & Distributors

Engine Wiring Harness

Intake Manifold Repair Kit

Pulley

Engine Components & Accessories

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Active Grille Shutter Actuator

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Auxiliary Water Pump

Drive Motor Inverter Cooler

Electric Engine Water Pump

Engine Coolant Air Bleeder Valve

Engine Coolant Pipe

Engine Coolant Shut Off Valve

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Expansion Tank

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Expansion Tank Mounting Plate

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Fan Pulley Bracket

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Fuel Cooler

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Overflow Hose Connector

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Radiator

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Radiator Control Fan Module

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Radiator Core Support Skid Bar Plate

Radiator Fan Cooling Motor

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Radiator Hose

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Engine Cooling

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The engine comprises many essential elements such as the lower cylinder block, upper cylinder head(s), and the cooling & lubricating systems. With A-Premium aftermarket engine components, you can expect that your engine deliver years of reliable performance. We offer a diverse selection of engine components from air filters and ignition coils (kits) to fuel pumps to cater to your needs.

BMW 645Ci Brake Master Cylinder