Angle Mounted Master Cylinder Bleeding Procedure All angle-mounted master cylinders. Unable to obtain a firm brake pedal when bleeding master cylinder on vehicle Cause: Air trapped in the upper end of the master cylinder past the secondary port. When bleeding brakes system, raise rear of vehicle until master cylinder bore is level as shown below. CAUTION: Some fluid should be removed from the reservoir to avoid spilling as vehicle is raised. Always flush entire brake system with approved fluid when any brake component is replaced. JDA5256 PT 10-0003
DIAGONAL SPLIT BLEEDING SEQUENCE FWD vehicles with diagonal split brake systems. Brake system won t bleed, uneven pad wear, low brake pedal, or warning lights that won t go out. Cause: Improper brake bleeding sequence. Brake systems on most FWD vehicles have been redesigned to insure adequate stopping power in the event of partial system failure. To ensure proper system performance these diagonal split systems require a special bleeding sequence, usually RR, LF, LR, RF. Refer to manufacture s bleeding sequence for your vehicle. When replacing brake components, always flush entire brake system with approved brake fluid from a sealed container. JDA5235 PT 10-0004
Brake Hose May Cause Low Pedal All vehicles with power brakes. How to diagnose a sinking, low or spongy brake pedal. 1. Begin by isolating the master cylinder. Remove the lines from the master cylinder and insert blocking plugs into the ports. Press on the brake pedal. If the pedal is firm and hard, the master cylinder is good. If the pedal still drops, either air is in the unit or it is bypassing internally. Bleed the unit or replace as necessary. Reconnect and bleed the system. 2. With a properly bled master cylinder test the brake hoses. Using a proper tool, carefully pinch off all the rubber brake hoses as close to the master cylinder as possible. Release one brake hose at a time. Press the brake pedal. If the brake pedal is firm and hard, move to the next circuit. Repeat until the circuit containing the defective component is located (the brake pedal will be soft or sinking). Replace defective components as necessary. 3. Flush the system thoroughly with fresh brake fluid from a sealed container according to the manufacturer s service procedures. Pinch off hose close to master cylinder Flush system with fresh brake fluid after repairs Contaminated Fluid JDA5237 PT 10-0005
Choose the Right Brake Fluid It Does Matter All vehicles. Choosing which type (DOT 3, 4, or 5) of brake fluid for your brake system. Does it really matter? YES! It s very important the fluid specified by the original vehicle manufacturers must be used. DOT 3 & 4 brake fluid is a mineral based fluid. DOT 5 is silicone based. Never mix the two types. DO NOT use DOT 5 in a vehicle equipped with ABS (Anti-Lock Brake System). Foaming of the fluid will occur due to the pulsed high pressure action of the ABS system under braking. To determine which fluid should be used for your vehicle, simply consult the shop manual or look on the master cylinder lid or reservoir body. Brake Fluid Specifications Located on Lid Caution: If two different brake fluids have been mixed, the brake system should be flushed, and fresh brake fluid recommended by the vehicle s manufacturer should be installed. JDA8338 PT 10-0006
Can I Mix Brake Fluid? All vehicles. Question: Can I mix brake fluid? Answer: NO! When servicing a brake system you must always replace the brake fluid using OE specified brake fluid. Replacing the fluid avoids contaminating the entire brake system. Mixing fluids or using petroleum based fluids will destroy seals and gaskets throughout the entire brake system (see example), causing catastrophic brake failure. This can result in vehicle damage and/or personal injury. Contaminated Good Mixing or using the wrong brake fluid will void the warranty. Always refer to manufacturer's specifications when selecting the proper brake fluid. Always use new fluid from an unopened container. MS9349 PT 10-0007
Brake Lock-up Nissan Quest and Mercury Villager (10-2637 & 13-2637) Cause: Nissan Quest/Mercury Villager minivans with ABS (up to the 2002 model year). Master Cylinder 10-2637 and 13-2637. Left front/right rear brake is locking up. Contaminated brake fluid may have blocked the ABS modulator valves or the Dampener Valve. The Dampener Valve is a component that is screwed into one of the outlet ports of the master cylinder. The brake line for the left front and right rear brakes come out of this part. Another possibility is ABS system component failure causing brake pressure not to be released. 1. The first step is to examine brake fluid condition for signs of debris and contamination; flushing and replace the fluid as needed. 2. Next verify there are no ABS codes. Faulty wheel sensors (code 21) can cause false ABS actuator operation resulting in wheel lock-up. Repair or replace as necessary, then clear ABS codes and verify operation. 3. Before replacing the master cylinder, the dampener valve, or the ABS Actuator, loosen the master cylinder so it can be pulled away from the brake booster to eliminate the possibility of brake pedal free play or a pushrod adjustment problem. While this type of problem usually affects all four brakes, it does allow the master cylinder and linkage to be isolated. If the brakes still do not release, loosen the brake line from the dampener valve and verify the brakes free up. If the brake fluid pressure is not releasing on its own, this may indicate a problem in the ABS actuator or the dampener valve that is blocking release of brake fluid pressure back to the reservoir. In most cases the cause of the lock-up is the accumulation of debris and contamination that is effecting the operation of the ABS unit or the dampener valves. Proper periodic flushing and replacement of the brake fluid will help avoid this lock-up problem. Please refer to your vehicle s service manual for specific diagnostic instructions. This ProTech bulletin is supplied as technical information only and is not an authorization for repair. JDB1230 PT 10-0009