Brake booster adjustment rod

Is there an adjustment on the booster between the master cylinder and the booster?

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Have 97 chevy Silverado1500...replaced master Cylinder, calipers and pads still not releasing fully and brakes get extremely hot


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james castle no there is not. The master cylinder is directly mounted to the output push rod of booster. Let us know what is going on with your brakes. There may be other things we can help you with.

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The previous answer is completely wrong.

YES there is an adjustment. It is the adjustment of the Booster pushrod which makes contact to the primary valve in the master cylinder.

Too much space between the tip of the rod to the valve, when in the INSTALLED position, will leave too much brake pedal play before the brakes will start to be applied.

However not enough space between the rod and master cylinder valve will preload the valve and the brakes, which could result in a dangerous situation.

Accurate measurement must be made before the master cylinder is bolted on, since the only way to adjust the rod is with the master cylinder unattached.

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NOTE: Correct push rod length is essential to reliable braking. If the rod is too long, it causes the

compensating ports in the master cylinder to be closed off, eventually resulting in brake drag. If the

push rod is too short, there will be excessive brake pedal travel and possible there will be a groaning

noise from the brake booster. Use the following procedure to check the push rod adjustment.

CAUTION: Wear protective goggles when performing the following procedure! Brake fluid may erupt

from the master cylinder with sufficient force to cause personal injury.

1. Remove the master cylinder reservoir cap or cover.

General Brake Booster Installation Instructions


2. While an assistant slightly depresses the brake pedal, watch for fluid to erupt in the reservoir

when the pedal is depressed 3/8” to 1/2”. This indicates correct push rod length. On dual

system master cylinder, fluid may spurt only from the front reservoir.

3. If the pedal travels more than 1/2” before master cylinder fluid erupts, the push rod is too

short. If nothing happens no matter how far the pedal is depressed, the push rod is probably

too long.

4. To adjust the push rod length, first remove the master cylinder from the power booster. Using

a pair of pliers, turn the push rod adjusting not in to shorten and out to lengthen the push rod.

5. If the push rod is nonadjustable, use shims between the master cylinder and power booster

to shorten it. If too short, remove existing shims or remove the push rod from the booster and

replace it with one of the proper length.

6. Install the master cylinder onto the power booster and recheck push rod length.

7. Connect the vacuum hose(s) to the power booster.

8. Reconnect the ground cable to the battery.

9. Make sure the braking system works correctly before moving the vehicle. If the pedal is soft or

has excessive travel, it may be necessary to bleed the entire braking system.

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