FAQ: Top Master Cylinder Questions

As a rule, always use the brake fluid recommended by O.E. which is stamped on the master cylinder lid.

Note: Always use new fluid from a sealed container.

Dot 3 and 4 are Glycol-based fluids and Dot 5 is a Silicone based fluid

Refer to the installation instruction sheet for special step bore bleeding process. Bench bleed first by slowly depressing brake piston then release slowly and waiting 20 seconds before you push again. NEVER pump piston/pedal with a step bore style master cylinder. Follow the same process on the vehicle.

Make sure when bench bleeding that you use a blunt tool (wooded dowel) when bench bleeding. Check booster for a defective push rod seal. If this seal is bad, it could suck the brake fluid out of the master cylinder.

The master cylinder is working correctly. Check for a faulty brake booster or frozen wheel cylinder/caliper.

First, check for air in the system. Make sure master cylinder is level when bleeding. Air will compress in a hydraulic system causing a low pedal. Then check for brake hoses swelling/expanding under pressure. Then check brake drums/discs for proper specifications. And then check brake material.

The right front brake not releasing is either a problem with the caliper or brake hose. If the master cylinder was defective, most likely both front brakes would not release.

Check the steering and suspension. Inspect both calipers for binding or sticky slides or pins. Check brake lining for oil/grease or uneven wear. Inspect brake hoses for restriction. Check for proper tire pressure.

Replace all brake fluid. Brake fluid is hygroscopic which means it absorbs moisture. Too much water in brake fluid will cause vapor lock and apply pressure to the wheels. Also check for proper push rod adjustments and stop light/cruise control switch adjustments.

Most likely, the fluid in the system is contaminated. The most common contamination is that petroleum-based fluid has been accidentally used in or added to the brake system. If that has happened it is almost certain that all rubber components in the brake system (hoses, seals, bladders) will need to be replaced after the system is completely and thoroughly flushed. If the contamination is due to moisture, rust and/or dirt, it might be possible to restore operation by flushing the system and replacing the brake fluid with fresh, clean fluid. Always use the brake fluid specified by the vehicle manufacturer. Always use fluid from a sealed container.

Simply plug the master cylinder ports and press the brake pedal. If the master cylinder is bypassing, the pedal will go down. If the pedal stops hard, the master cylinder is OK.