How to Adjust Brake Booster Push Rod Properly in Your Car

Last Updated on October 8, 2019 by themechanic

The braking system of a vehicle is designed to be simple for the driver to use. When you apply just a little bit of pressure to the brake pedal, the vehicle will slow down. There is a reason that you don’t need to apply much force to the brake pedal to accomplish this. Every braking system has something called a brake booster to make braking easier for the driver. It is like how power steering makes steering easier. Since the braking fluid is under high pressure, there is an intake manifold vacuum used by the brake booster to overcome the pressure.

Basically, as you step on the brake pedal, the brake booster compresses a diaphragm with the help of the intake manifold vacuum. This causes a push rod to push against the brake master cylinder piston. Once that happens, the high pressure pushes the brake fluid through the brake lines. This causes the pressure of your foot on the brake pedal to be amplified as more brake fluid flows into the wheel cylinders and brake calipers. This is when the brake pads make contact with the brake discs, or when the brake shoes expand and make contact with the brake drums.

For this entire process to work smoothly, there needs to be the right amount of space between the brake master cylinder piston and the brake booster. You can set the right space by adjusting the brake poster push rod. It is important that you adjust it accordingly or else you’ll have a low brake pedal and/or brakes that simply drag as you step on the pedal. This can become a driving hazard for you and anyone else around you. Therefore, the length of the brake booster push rod must be adjusted properly. Use the steps below to guide you.

Below are the 5 steps to adjusting your brake booster push rod.

1) Set the Right Gear – Before you even attempt to adjust the brake booster push rod, there are some precautions that you need to take. First, make sure the car shift stick is set to Neutral or Park (usually Park is the best choice). You should also set the emergency brake as well.

2) Disconnect Battery – It is important that your vehicle doesn’t have any power or electricity in its components while you’re making the adjustment. To accomplish this, raise the hood of your vehicle and disconnect the battery terminal from the negative side. You don’t need to take the battery out just as long as the negative cable is not attached.

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3) Determine the Proper Push Rod Length – You don’t want the push rod to be too long because it will cause your brakes to drag. You don’t want it to be too short either because your brakes will get noisy. So, you need to set the length just right. A push-rod depth gauge should help you determine this. In most cases, the length will be roughly .020”.

4) Adjust the Push Rod – To access the push rod, the cylinder needs to be disconnected first. You will need to use pliers for the push rod to be adjusted accordingly. The push rod has a nut which can be turned outward or inward to increase or decrease its length. Shims can be used to adjust the push rod if you can’t do it with the pliers.

5) Reconnect the Negative Battery Cable – If you have properly adjusted the push rod length, now you just need to reconnect the cylinder and then the negative battery cable. Close the hood and then go to test your brakes on the road. You should find them working smoothly with no strange noises at all.

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