Car Repairs how to Replace a Brake Master Cylinder
Replacing the brake master cylinder is a job that anyone can do with the right tools and a little time. Replacing your own brakes can save you time, money, and a trip to a garage. The only reason not to replace it yourself is if the warranty won't cover repairs done by the owner. If you are unsure what your warranty covers check the owners manual for your vehicle.
There are several items you will need to replace the brakes. The necessary items are a socket or wrench set, pliers, flair nut wrench, a fender protector, replacement cylinder, brake fluid, and spray penetrating oil. As with any repair job safety glasses are recommended.
Begin by locating the master cylinder inside the vehicle. Compare the new cylinder and the old one to be sure they are the same part.
Put something over the body panels to protect the car from dripping brake fluid. If it gets onto the paint the corrosive components in the fluid will eat through it. Also place a piece of news paper below the master cylinder to protect the engine from fluid that drips in the process.
Before removing the old master cylinder check to be sure the new one comes with a brake bleeding kit. Most of them do however you wouldn't want to get the old one off and realize you can't put the new one on yet.
To remove the old cylinder use a wrench to loosen the nut holding the brake lines in place. If you are unable to remove the the fittings use penetrating oil to loosen them. When the brake lines have been disconnected use a small square of tape over each line to prevent dirt or other contaminates from getting into the lines.
If the car has an attached push rod actuator you will need to disconnect it from the brake pedal.
Remove the mounting bolts from the fire wall or power brake booster.
Pull the cylinder forward upward away from mounting bolts. Be careful not to spill the fluid since it is corrosive.
Prepare the new cylinder for instillation by bench bleeding it.
- To bench bleed the new cylinder is a simple process.
- Secure it horizontally and level in a bench vise.
- Trim the ends of the valves to eliminate back pressure from the piston return stroke.
- Fill the reservoirs with new break fluid.
- Slip both ends of the rubber hose over the adapter valves.
- Holding the hose above the cylinder cut it as close to the middle as possible then insert the freshly cut ends into corresponding reservoirs.
- Hold the ends of the hose against the divider of the cylinder.
- Then run the piston through a few cycles holding it securely open on the in stroke and closed on the out stoke until there are no more air bubbles in the line.
- Tie the hoses in a line to keep them from dripping and replace the cylinder cover.
Install the cylinder while making sure the push rod is in the right position.
Reconnect the actuator to the brake petal.
Replace mounting nuts.
Remove the hoses and bleeding adapters and loosely replace the brake lines. Have a helper slowly depress the brake pedal until the fluid starts to drip around the line. Then tighten the fittings. Remember not to release the brakes until both sides are tightened.
Check the fluid and make sure it is up to a quarter of an inch from the top of the cylinder. Top off the brake fluid as needed.
Pump the brakes several times until they feel firm.
When you have finished all of these steps there is only one thing left to do. It's time to test drive. In this case you are not trying to see how the car drives. You are testing just the brakes. Start with a few quick stops at a low speed. If everything seems working normally take it for a lap around the block just to be sure.
