Technical bulletins (CoF)

9 Park brake inspection and 4085D requirements


VIRM reference

Heavy vehicles 8-1: Service brake, parking brake and heavy vehicle emergency brake

This bulletin has been produced to supplement information provided to the repair industry and should be considered in inspecting all parts of a heavy vehicle park brake system.

Introduction

The introduction of the 4085D Operator statement of compliance with maintenance requirements for parking brake assemblies form came about due to several run-away trucks that have led to a fatal or serious injury crash where the park brake has been a contributing factor. Issues with the air-powered park brake application valve beside the driver’s seat and the Cardan shaft park brake system found on many trucks, buses and motorhomes have been the main concern, however all park brake systems are susceptible to wear and degradation that can affect the holding performance of the brake.

Investigations have found the air park brake valve wears out internally through dust and moisture ingress over time and can cause the valve detent to stick in the neck portion and not fully engage with the lock. As the driver gets out of the vehicle the valve can be knocked or on occasions get caught in the driver’s clothing releasing the lever.

There are also problems that have been traced to Cardan shaft park brakes not holding the vehicle even when the lever has been applied. This is due to several factors including a lack of maintenance that reduces the ability of the brake to hold the vehicle and its load, especially on an slope or instances where the lever feels fully applied but resistance and wear in the linkages reduces the application force at the brake unit.

The 4085D form

The 4085D Operator statement of compliance with maintenance requirements for parking brake assemblies form is designed to be used by a heavy vehicle operator where their powered heavy vehicle park brake has failed a compliance brake test at In-service certification (CoF B) inspection. The operator must have the park brake system repaired or serviced and return the completed form to the VI to show that the park brake system has been inspected and serviced by a technician and is in good working condition.

Parking brake inspection

What are the indicators that might make a vehicle inspector doubt the condition of a park brake assembly?

A park brake system is generally easily serviced (except for some sealed park brake air valves) but items that are susceptible to wear, degradation and ingress of dust and dirt need to be maintained to ensure park brake performance meets the required standard.

Not all park brake assemblies are easily accessible but visual signs that may point to no recent maintenance include:

  • rusted bolts, screws, clevis pins or linkages which activate the park brake.
  • dust, dirt, seat foam or general rubbish around the lever assembly.
  • excessive resistance in applying the park brake.
  • excessive contamination due to oil leaks or other debris.
  • a lack of feel from the detent or lock position when applying the lever of an air park brake valve.
  • The park brake fails to hold the vehicle in the stall test.

Are there any parts within the assembly that are more prone to cause problems than others?

The risk is more with the age of the vehicle (particularly older vehicles that have not been regularly serviced) and those working in dusty operations such as concrete mixer trucks and quarry trucks. Pay particular attention to the application valve or lever and any detents, ratchet or other mechanical locks designed to hold the lever in its applied position.

Are there specific makes/models that should be paid close attention to?

Vehicle inspectors should pay attention to all park brake systems. All makes or models should be treated equally. As mentioned above, vehicles working in dusty operations such as concrete mixer trucks and quarry trucks could be a higher risk.

Waka Kotahi has published safety alerts covering some Nissan trucks and on Cardan shaft park brakes that alert owners to maintenance and adjustments that should be carried out.

4085D requirement scenarios

If a vehicle inspector finds defects in the park brake components or the vehicle fails a stall test, they can request that the 4085D form be presented to provide proof of inspection and servicing to the manufacturer’s specifications, the vehicle inspector may issue a 28-day permit to allow the operator to have the park brake maintenance carried out and get a 4085D form completed.

When do you need to ask the operator of a powered heavy vehicle (a heavy truck, bus or motorhome above 3500kg) for a 4085D form?

  • The vehicle fails the CoF inspection on park brake condition or fails a stall test for park brake performance (do not issue for RBM fails). The VI may issue a 28-day CoF permit.
  • The vehicle passes the stall test for park brake performance but fails on another park brake CoF item and the VI has doubts about the park brake maintenance.

When do you NOT need to ask the operator of a powered heavy vehicle for a 4085D?

  • The vehicle fails an RBM brake test for park brake performance but passes all other CoF requirements, and the VI has no doubts about park brake maintenance, the vehicle goes through the normal recheck process.
  • The vehicle passes an RBM brake test for park brake performance but fails on another CoF item, and the VI has no doubts about the park brake maintenance. The VI fails the CoF for the other item(s) and the vehicle goes through the normal recheck process.

Page added 1 May 2023 (see amendment details).

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