I have 98 GMC 2500 with hydraulic brake assist and when I have a load my brake become soft with little stopping ability and the power steering in one case was lost. My question is the pump, master cylinder or the brake boost the problem? 
Brake booster
- Thread starter dogday
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Molson02536
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I have 98 GMC 2500 with hydraulic brake assist and when I have a load my brake become soft with little stopping ability and the power steering in one case was lost. My question is the pump, master cylinder or the brake boost the problem?
The brake hydro booster on your vehicle provides additional braking power to help reduce the amount of effort needed on your part to slow down your vehicle. The booster works on hydraulic pressure generated by the power steering pump. When you press on the brake pedal, the booster creates additional force on the braking system. That, along with the hydraulic fluid in the brake lines, creates a tremendous amount of force on the brake calipers and pads. When your brake hydro booster is malfunctioning, braking will be be much more difficult. Before replacing the booster, troubleshoot the problem.
You probably have a problem with the pump, or something with the hydro boost, had both of them fail on several occurrences. quite common.
The main shaft where the pulley rides, it usually breaks where it is splines internally to the pump. Take a pry bar and push against the pulley to pull it away from the pump. If it moves away from the pump, you know its a bad pump which is really a common failure.
Test:
1. Get in your vehicle, pump the brakes 5 or 6 times and hold the brake pedal with the car engine off to discharge the hydro booster accumulator.
2. Start your vehicle's engine.
3. Wait for the brake pedal to fall slightly, then rise (push against your foot). If it does not, you may have an internal seal failure in the brake booster system and will need to replace the booster.
4. Pump the brakes several times with the engine on.
5. Shut the vehicle off, and wait for an hour to an hour and a half.
6. Pump the brake pedal without starting the engine. You should be able to pump the brakes 2 to 3 times before significant pressure builds up inside the system. If it doesn't, have your hydro booster serviced or possibly replaced by a professional mechanic.
Good luck and be safe.
