Adjusting master cylinder pushrod length

Adjusting the pushrod length of the vacuum brake booster is the process of adjusting the movement of the piston in the master brake cylinder. The piston lever is the connection between the brake pedal and the piston of the master cylinder. The length of the lever determines the correctness of the brake system, the correct position of the pedal, and the correct operation of the master brake cylinder.

The length of the thrust lever defines the movement of the piston in the master brake cylinder. If the length is too long, the lever prevents the piston from returning to the starting position after braking, which prevents the brake pressure from being completely lowered and the brake from returning to the starting position. When the length of the lever is too short, we have too much free play in the brake pedal and may occur noise from the vacuum brake booster.

Master cylinder pushrod length is defined for each vehicle. We perform the adjustment only when we determine that someone before us has adjusted the length, after repairing, adjusting the brake pedal, or replacing the vacuum brake booster. Replacing the master cylinder does not require adjusting the pushrod length.

Adjusting pushrod length is done with a special tool. The tool consists of spacers on both sides and a movable measuring rod in the middle. It is first mounted on the master brake cylinder at the part where the pushrod enters. Release the rod screw and gently push it to touch the cylinder piston. This position of the rod is fixed with a screw.

Then the other arm of the measuring tool is placed on the vacuum brake booster towards the pushrod. If the tip of the pushrod does not touch the measuring rod, it is necessary to adjust the length of the pushrod. Unscrew the lock nut and place the push lever in position to touch the dipstick. The adjusted position of the pushrod is ensured by turning the lock nut.

Measuring tool for adjusting pushrod length

In the absence of a special tool, a caliper can be used to adjust the length of the pushrod.

To adjusting the master cylinder pushrod length, follow these steps:

Removing the master cylinder

Remove the master cylinder from the vacuum brake booster. Check that the brake pedal to the starting position.

Adjusting pushrod length

Measure the length of the pushrod on the master brake cylinder with a suitable measuring tool. Place the measuring tool on the vacuum brake booster. Unscrew the lock lever lock nut. Adjust the lever to the required length. Tighten the lock nut and recheck the length of the pushrod.

Installing the master cylinder

Return the master cylinder to the vacuum brake booster. Check the movement of the pushrod and piston.