Here you will find useful basic information and valuable tips all about damage assessment of parking brakes.
Important safety information
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.
The handbrake, also known as the parking brake, has the task of securing a stationary or parked vehicle and of preventing it from rolling away when no driver is present in the vehicle. With the mechanical handbrake, the braking force is transferred to the wheel brakes of the rear axle via cables when the handbrake lever is operated using muscular pulling force.
A defective handbrake cable first becomes apparent when the parking brake fails.
The following repair notes are based on the example of a Mazda 6 but they can also be applied to identical vehicle models. In our case example, the handbrake lever cannot be operated. The service brake on the rear axle works trouble-free and showed sufficient braking values on the brake test stand.
Using the example of a Mazda 6, we show in our video how to check the handbrake for faults and how to replace the handbrake cable professionally.
In order to determine the cause of the defect, all components of the parking brake should now be checked.
Damage to the dust protection sleeves on the cables was found here (Figure 1).
Release the handbrake cable for further diagnosis
Then check the mobility of the handbrake levers on the rear brake callipers
The handbrake levers and operating levers on both brake callipers move freely and show no visible defects.
To remove the handbrake cable package, carry out the following work
After dismantling, the cause could clearly be attributed to the handbrake cable. The cable could no longer be moved in the Bowden cable. Internal impurities and corrosion have led to an impairment of operating movement (Figure 2).
Before the new handbrake cable is installed and adjusted, the mechanical adjustment devices in the two brake callipers of the rear axle should first be checked and reset. Correct adjustment of the parking brake is only possible if the parking brake Bowden cables and all moving parts of the parking brake move easily and are functional.
To do this, remove the brake calliper and operate the mechanical lever on the brake calliper until the brake piston extends slightly. After successful testing, turn the piston back completely using a reset tool (Figure 3).
While this task is being carried out, all other components such as brake blocks/pads or guide bolts should be checked for wear and functionality at the same time. Worn or defective components should be replaced.
Put brake callipers back together and reinstall. Then bring the brake pistons into their working position by means of light pedal pumping.
Reinstall the new handbrake cable in reverse order.
The handbrake lever travel should be adjusted in such a way that a blocking of the brake is achieved between 4 - 7 detents.
The indicator lamp should now light up. The wheels must now still turn freely and the rear wheel brakes not drag.
After the basic adjustment, automatic readjustment in the brake callipers of the rear wheel brake means that readjustment of the handbrake is no longer necessary.
Finally check the effectiveness of the handbrake on the brake test stand.
In connection with this information, please also observe the maintenance and repair instructions of each individual vehicle manufacturer!