1994 MAZDA MX-5 Workshop Manual

BRAKE SYSTEM CLEARANCE (0) CLEARANCE (C) CLEARANCE (B) 4. Remove the SST from the power brake unit without dis- turbing the adjusting nut. Set the SST onto the master cylinder as shown in the figure. -J Caution When pushing only use enough pressure to bot- tom the rod in the piston. If too much pressure is applied a false reading will occur. 5. Push lightly on the end of the SST gauge rod to be sure it is bottomed in the master cylinder piston, but do not push so hard that the piston mores. Note Any clearance between the SST body and the adjusting nut (clearance B) or between the body and the master cylinder (clear- ance C). Adjust the push rod as necessary as outlined in "Adjustment" below. I Measurement 1 Push rod I I Clearance at (B) I Too short I Adjustment The threads of the push rod are specially designed so that the bolt becomes harder to turn past a certain point. This is to prevent the bolt from coming loose. Turn the bolt only within this range when adjusting. Clearance at (C) No clearance at (B) or (C) '.A Clearance at B 1. Push lightly on the end of the SST gauge rod, and mea- sure the clearance between the adjusting nut and the SST body. Too long OK 2. Using the SST, turn the nut to lengthen the power booster push rod an amount equal to the clearance mea- sured at B. Clearance at C 1. Measure and record height Dl of the gauge rod. Gartner Banana

BRAKE SYSTEM ADJUSTING NUT 1 2. Turn the adjusting nut until the SST body sets squarely on the master cylinder. (Turn only enough for the body to touch.) I 3. Measure and record height 02 of the gauge rod. I 4. Subtract Dl from 02 and, by using the SST, turn the nut to shorten the power booster push rod an amount equal to the sum. Inspection Fluid level sensor connector 1. Disconnect the sensor connector. 2. Connect an ohmmeter to the connector. 3. Starting with the fluid level above the MIN mark on the reservoir, verify that there is no continuity. 4. Remove the brake fluid and verify continuity when the level is below the MIN mark. 5. Replace the sensor if necessary. Gartner Banana

BRAKE SYSTEM Disassembly / Assembly / lnspection 1. After removing the brake fluid, disassemble in the order shown in the figure. 2. lnspect all parts and repair or replace as necessary. 3. Assemble in the reverse order of removal, referring to Assembly Note. Caution The brake master cylinder Is made of aluminum, and can be easily damaged by tightening in a vise. When securing the master cylinder in a vise, tighten only the master cylinder flange. 1. Fluid level sensor connector 7. Snap ring Inspection ................... page P-17 8. Snap ring and spacer (ABS) 2. Screw 9. Primarv ist ton assemblv 3. Reservoir assembly inspect for abnormal wear, rust, and damage Inspect for damage and deformation 10. Secondary piston assembly 4. Bushings Inspect for abnormal wear, rust, and damage 5. Stop screw and O-ring 11. Master cylinder body e Assembly Note .............. page P-19 Inspect for abnormal wear, rust, and damage 6. Stop pin and O-ring (ABS) Replace unit as an assembly if damaged Assembly Note .............. page P-19 Gartner Banana

BRAKE SYSTEM P Assembly note Stop screw and O-ring 1. Push the primary piston assembly in fully. 2. Install and tighten a new O-ring and the stop screw. 3. Push and release the piston to verify that it is held by the stop screw. Stop pin and O-ring (ABS) 1. Install the secondary piston isembly with the piston hole facing the stop pin. 2. Install and tighten a new O-ring and the stop pin. 3. Push and release the piston to verify that it is held by the stop pin. Gartner Banana

P BRAKE SYSTEM k FIRST PEDAL VACUUM GAUG DEPRESSION FORCE GAUGE POWER BRAKE UNIT Quick Inspection, On-vehicle Power brake unit function check (Simple method) ii Step 1 1. With the engine stopped, depress the pedal a few times. 2. With the pedal depressed, start the engine. 3. If immediately after the engine starts the pedal moves down slightly, the unit is operating. Step 2 1. Start the engine and let it run 1 or 2 minutes. 2. Stop the engine. 3. Depress the pedal with the usual force. 4. If the first pedal stroke is long and becomes shorter with subsequent strokes, the unit is operating. 5. If a problem is found, inspect for damage or improper connection of the check valve or vacuum hose. Repair if necessary, and inspect it once again. Step 3 1. Start the engine. 2. Depress the pedal with the usual force. 3. Stop the engine with the pedal depressed. 4. Hold the pedal down for about 30 seconds. 5. If the pedal height does not change, the unit is operating. ,, 6. If there is a problem, check for damage or improper con- nection of the check valve or vacuum hose. Repair if necessary, and check once again. If the nature of the problem is still not clear after following the 3 steps above, follow the more detailed check described in "Method using tester," below. (Method using tester) Connect the SST, vacuum gauge, and pedal depression force gauge as shown in the figure. After bleeding the air from the SST, conduct the test as described in the 3 steps below. Inspection using gauges Connect the SST gauges, a vacuum gauge (A), and a pedal depression gauge (B) as shown. Bleed the air from the SST gauges before performing the following tests. a) Checking for vacuum loss Unloaded condition 1. Start the engine. 2. Stop the engine when the vacuum gauge indicates 66.7 kPa (500 mmHg, 19.7 inHg). 3. Observe the vacuum gauge for 15 seconds. If the gauge indicates 63.4-66.6 kPa (475-500 mmHg, ,, 18.7-19.7 inHg), the unit is operating. Gartner Banana

BRAKE SYSTEM P (20 kgf, 44 Ibf) (20 kgf, 44 Ibf) Loaded condition 1. Start the engine. 2. Depress the brake pedal with a force of 196 N (20 kgf, 44 Ibf). 3. With the brake pedal depressed, stop the engine when the vacuum gauge indicates 66.7 kPa I500 mmHg, 19.7 inHg). 4. Observe the vacuum gauge for 15 seconds. If the gauge indicates 63.4-66.6 kPa (475--500 mmHg, 18.7-19.7 inHg), the unit is operating. b) Checking for hydraulic pressure 1. If with the engine stopped (vacuum 0 kPa (0 mmHg, 0 inHg}) the fluid pressure is within specification, the unit is operating. 1 Pedal force Fluid pressure 2. Start the engine. Depress the brake pedal when the vac- uum reaches 66.7 kPa (500 mmHg, 19.7 inHg). If the fluid pressure is within specification, the unit is operat- ing. 1 96 N {20 kgf, 44 Ibf) I Pedal force I Fluid pressure I 1,079-1,177 kPa {I 1-1 2 kgf/cm2, 156-1 71 psi) lnspection of Check Valve 196 N {20 kgf, 44 Ibf) Note There is an arrow on the hose to indicate direction of hose installation. 5,199--5,494 kPa {53-56 kgf/cm2, 754--796 psi} lnspection 1. Disconnect both ends of the vacuum hose. 2. Apply suction and pressure to the hose from the engine side. Verify that air flows only toward the engine. If air passes in both directions or not at all, replace the vac- uum hose (along with the check valve). Gartner Banana

P BRAKE SYSTEM Removal / Installation 1. Remove in the order shown in the figure. 2. Install in the reverse order of removal. 3. Take the following steps after installation: (1) Check and adust the push rod and piston clearance. (Standard: refer to page P-12 1 ABS: refer to page P-15.) (2) Add fluid and bleed the air. (Refer to page P-7.) (3) Check all parts for fluid leakage. (4) Check and adjust the brake pedal height and free play. (Refer to page P-9.) (5) Make an on-vehicle check of the unit. (Refer to page P-20.) (6) Check that the vacuum hose does not contact other parts. ABS 1~22 (1.3--2.2,~.&16} STANDARD 35UOPX-01 1. Fluid level sensor connector 5. Clevis tin 2. Brake pipe and proportioning bypass valve 6. Power 'brake unit 3. Master cylinder 7. Gasket 4. Vacuum hose with check valve Apply sealant to the gasket contact surface Gartner Banana

BRAKE SYSTEM P MASTER CUUNDER PRESSURE kPa #gflcm2, psi) 15UOPX-025 Replacement PROPORTIONING BYPASS VALVE Inspection When disconnecting and connecting the brake pipes, do so by using the flare nut wrench SST. 1. Connect the SST and the adapters to the brake pipes as shown in the figure. 2. Bleed the air from the brake system. (Refer to page P-7.) 3. Measure the fluid pressure from the master cylinder and to the rear brakes. If not as specified, replace the valve assembly. Specification 4. Add brake fluid and bleed the air. (Refer to page P-7.) 5. Check the brake lines for fluid leakage. Fluid pressure kPa (kgf/cm2, psi) Caution Brake fluid will damage painted surfaces. If brake fluid does get on a painted surface, wipe it off immediately. A A' I B 1. Remove in the order shown in the figure, referring to Removal Note. 2. Install in the reverse order of removal, referring to lnstallation Note. 3. After installation: (1) Add brake fluid and bleed the air. (Refer to page P-7.) (2) Check the brake lines for fluid leakage. 6' 1. Brake pipe 2. Bolt Removal Note ............... page P-24 3. Proportioning bypass valve Installation Note ............. page P-24 Gartner Banana