Q - Hydro-Boost Brake System Operation Suspect

Q1- Basic Check
- Ignition switch should be "OFF".
- Press and release brake pedal several times to deplete all hydraulic pressure from the hydro-boost power brake booster.
- Press and hold brake pedal with light pressure.
- Start the engine.
- Does the brake pedal fall slightly and hold and is less pressure now required to hold brake pedal at the new position ?
YES - Hydro-boost Brake Booster is OK.
NO - Go to Q2.

Q2- Brake Hydraulic Leak Check
- With the engine running, press and release brake pedal several times.
- Hold brake pedal down with medium pressure, 111-156 N (25-35 lbs.)
- Does the brake pedal move toward the floor ?
YES - Go to Q3.
NO - Go to Q4.

Q3- Leak Check - Brake Fluid Lines
- Check for leaks at brake lines, including brake master cylinder and brake hoses.
- Do components check OK ?
YES - Service brake Master Cylinder as required. Perform Brake Master Cylinder By-pass Condition Test. Bypass Conditions Test
NO - Service Brake Hoses and Brake Lines as required. Hydraulic System

Q4- Check Hydro-boost Connections
- Clean the hydro-boost brake booster, power steering pressure hose, power steering gear pressure hose and power steering return hose and connections.
- "START" the engine and "RUN" at idle.
- Check hose connections for leakage.
- Do hose connections check OK ?
YES - Go to Q5.
NO - Service hoses and connections as required to correct leakage.

Q5- Hydro-boost Leak Check

CAUTION: Do not hold the brake pedal at 444 N (100 lbs) for more than 5 seconds at a time.

- With engine running at idle;
- Apply brake pedal with approximately 444 N (100 lbs) of force and hold.
- Check hydro-boost unit input seal, housing seal, accumulator seal, piston seal and spool plug seal for leakage.
- Is Hydro-boost unit free of leaks ?
YES - Go to Q6.
NO - Replace Hydro-boost Brake Booster.

Q6- Reserve Retention Check
- With engine running at idle;
- Charge system to pressure by holding the steering wheel at stop or by pressing the brake pedal with approximately 444 N (100 lbs) of force.
- Turn ignition switch to "OFF".
- Wait 8 to 12 hours.
- Press brake pedal and observe it there is any power brake reserve.
- Is there any power brake reserve ?
YES - Hydro-boost brake booster is OK.
NO - Replace the Hydro-boost Brake Booster.