How to Rebuild a Hydraulic Pump

What You'll Need
Car jack and jack stands
Lug wrench
Master cylinder rebuild kit
Inside snap-ring pliers
Brake fluid
Shop rags
Flare-nut wrenches

If the hydraulic pump in your car's master brake cylinder becomes defective, it can cause many problems with your brake system. Therefore, here is a handy step-by-step guide that will show you how to rebuild your car's master cylinder.

Step 1 - Purchase a Master Cylinder Rebuild Kit

Purchase a Master cylinder rebuild kit from a local auto parts store or online. Make sure to buy a rebuild kit that is compatible with your vehicle.

Step 2 - Raise the Vehicle

Use the car jack to jack up the vehicle, and then place jack stands underneath it so you can work under the car.

Step 3 - Remove the Tires and Wheels

Use the lug wrench to remove the lug nuts on your wheels, and then remove them from your vehicle and set them aside.

Step 4 - Remove the Hydraulic Brake Hoses

Spray some WD-40 or penetrating spray on the nuts used to connect the brake lines to the master cylinder. Then, disconnect the hoses from the master cylinder.

Step 5 - Remove the Brake Fluid Level Sensor

Remove the retaining clip that attaches the brake fluid level sensor to the brake fluid reservoir. Then, remove the brake fluid sensor from the vehicle.

Step 6 - Remove the Brake Fluid Reservoir

Remove the screws or bolts that attach the brake fluid reservoir to the master cylinder. Then remove the reservoir and set it aside.

Step 7 - Remove the Master Cylinder

Loosen the bolts that hold the master cylinder in place and remove it from the engine area.

Step 8 - Rebuild the Master Cylinder

Remove the snap ring from the master cylinder and discard it. Once you remove the snap ring, the piston will pop out of the master cylinder. Pull the piston from the master cylinder and discard it as well.

Apply lubrication to the new piston and then insert it into the master cylinder. Push the piston and as far as it will go, and then lock it with the new snap ring. (Note - You can also change the seals in the master cylinder as well if they appear to be worn.)

Step 9 - Installed New Master Cylinder

Take the bolts that you removed earlier, and bolt in the new master cylinder.

Step 10 - Reconnect Hoses

Connect the hydraulic brake hoses to the new master cylinder and tighten them with a wrench.

Step 11 - Reinstall Brake Fluid Reservoir and Fluid Level Sensor

Attach the brake fluid reservoir to the new master cylinder with the bolts or screws that you removed earlier. Then, use the retaining clip and reattach the fluid level sensor to the brake fluid reservoir.

Step 12 - Add Brake Fluid

Fill the brake fluid reservoir with brake fluid.

Step 13 - Bleed the Brakes

Remove the bleeder valve stem from the brake caliper that is closest to the new master cylinder. Then, have someone apply pressure to the brakes in order to bleed the brake system. Finally, replace the the bleeder valve stem or screw. After you finish one, do the same with the other calipers on the vehicle.

Step 14 - Install Tires and Wheels

Put the tires and wheels back on the vehicle, and tighten them with the lug wrench.

Step 15 - Lower the Vehicle

Remove the jack stands and lower the vehicle down onto the ground.