How to Perform a Hydraulic Pressure Test
If you are having problems or concerns with the disc brakes in your vehicle, you can perform a hydraulic pressure test to gauge the hydraulic pressure created by the master cylinder in your car. This will give you a good indication if enough pressure is being created by the hydraulic pump, or, in some cases, it will let you know if too much pressure is being supplied to the brake calipers in your car. So, here is a simple step by step guide that will show you how to test the hydraulic pressure in your car's brake system.
Step 1 - Obtain a Brake Pressure Test Kit
If you don't already have a hydraulic brake pressure test kit, you'll need to buy one at a local auto parts store or online. When shopping for a test kit, choose one that has multiple adapter fittings to make sure it will work with your car.
Step 2 - Jack Up the Vehicle
Jack up the car with a car jack and place it on jack stands so that you can work under the vehicle.
Step 3 - Remove Tires and Wheels
Use the lug wrench to remove the tires and wheels from the vehicle.
Step 4 - Remove Bleeder Valve Screw
Locate the bleeder valve screw on your brake caliper. It may be a screw or small bolt, so use the appropriate tool to remove it.
Step 5 - Attach Pressure Test Gauge to Caliper Bleeder Valve
Once you have removed the bleeder valve screw, find the correct adapter fitting and attach it to the pressure gauge. Then, connect the pressure gauge to the bleeder valve stem on your brake caliper.
Step 6 - Apply Pressure on Brake Pedal
Have your assistant step inside the vehicle begin applying pressure to the brake pedal.
Step 7 - Read Pressure Test Results
Once your assistant places pressure on the brake pedal, you should notice that the pressure indicator on the gauge begins to rise. Most pressure gauges will have a highest pressure point indicator, which will allow you to keep track of the highest pressure level of the hydraulic fluid moving through your brake system. This is the number you can use to compare pressure levels in your car owner's manual to determine if your car's hydraulic brake pressure is at an appropriate level.
Step 8 - Remove Pressure Test Gauge
Disconnect the pressure gauge from the brake caliper bleeder valve.
Step 9 - Bleed the Brake System
Since you have opened the hydraulic brake system in the vehicle, you'll need to bleed the brakes. Therefore, have your friend apply pressure to the brake pedals while the bleeder valve screw is open. Once you have completed bleeding the brakes, close the bleeder valve screw.
Step 10 - Add Brake Fluid
Fill the brake fluid reservoir in your vehicle with DOT 4 specification brake fluid.
Step 11 - Test the Brakes
Have your friend again test the brake pedal to see if the pedal feels spongy. If it does, you will need to bleed the brakes again.
Step 12 - Replace Tires and Wheels
Reinstall the tires and wheels, and tighten with the lug wrench.
Step 13 - Lower the Vehicle
Remove the jack stands and lower the vehicle.