Regular vehicle maintenance is sound business practice that ensures vehicles use fuel efficiently and prevents avoidable and costly breakdowns.
While routine maintenance is straightforward, this section outlines current issues that are beyond routine maintenance requirements that all those with an interest in the safe operation of heavy vehicles need to be aware of.
Safety alert: Avoid park brake failures
Park brake control valve maintenance and operational requirements for Nissan CK330, CW330, CW380, CW400, CG380, CW400 and CG400 vehicles manufactured between 1993–2005.
The Nissan Diesel Owner’s Manual recommends that the park brake hand control valve is overhauled at 12-month intervals. It also recommends that the valve’s operation is thoroughly checked by a qualified diesel technician when the vehicle is being serviced or if there is concern about its operation.
Read our safety alert information sheet about steps to take to avoid park brake failures. [PDF, 526 KB]
Safety alert: Transport Agency urging checks of truck drawbeams
The Transport Agency is investigating a catastrophic failure of a truck drawbeam that resulted in a laden heavy trailer separating on 18 October 2016.
Urgent work is underway to identify any other affected trucks so that they can be checked, with one already withdrawn from the same fleet where the drawbeam showed signs of fatigue cracks.
In the meantime, this safety alert is asking truck operators, service personnel and vehicle inspectors to check for signs of cracks in drawbeams.
Read our safety alert information sheet about the Transport Agency urging checks of truck drawbeams. [PDF, 796 KB]
Safety alert: Bolt-in tow-eye security
This safety alert has been issued by the NZ Transport Agency following recent incidents where heavy trailers have separated from the towing vehicle, specifically where the drawbar was fitted with a bolt-in tow-eye which pulled out.
What you should do:
- Check the security of the towing eye as part of the daily walk around.
- If there is any sign of it being loose (eg fretting, shiny, rusting etc) the tow-eye and nut must be replaced – under no circumstances is it to be tightened.
- When the tow-eye and nut is replaced, the nut must be torqued to the manufacturer’s recommendation (including a greased thread) and then if necessary taken to the next castellation – in no circumstances backed off.
- Following initial installation the nut should be re-torqued at the lesser of 5000km or as directed by the manufacturer. If it moves it must be re-torqued. Note: this is the only time that re-tightening is permitted.
- One manufacturer recommends checking the tightening torque of the castellated nut every 15,000km. The Transport Agency encourages all operators to follow this recommendation. If the nut is found to be loose the complete towing eye and nut must be replaced.
Read our safety alert information sheet about bolt-in tow-eye security [PDF, 404 KB]
Using safety chains on heavy trailers
Some operators have begun fitting safety chains between their heavy trucks and trailers to provide an additional safety backup between the primary coupling and the breakaway brake function. Safety chains allow a driver to bring a trailer to a controlled stop in the event of primary coupling failure, provided guidelines are met.
The Transport Agency reiterates that it is still comfortable with the current practice of using a primary coupling and breakaway brake.
However, for operators who want an additional level of safety, the installation of safety chains is a safe and legal option. The following guidelines must be followed otherwise there is risk of not being able to bring a trailer to a controlled stop.
Read our guidelines about using safety chains on heavy trailers. [PDF, 264 KB]
Skid plate corrosion
King pins and skid plates need appropriate inspection and maintenance. This is especially important where moisture and debris can accumulate above the upper surface of the skid plate and the design makes it difficult or even impossible for inspection to be carried out.
In these circumstances the potential for corrosion and eventual structural failure and resultant detachment from the towing vehicle is a significant risk. Operators, drivers and mechanics, as well as trailer designers, certifiers and vehicle inspectors, all need to take appropriate action to ensure trailer detachment does not occur.
Read our information sheet about skid plate corrosion [PDF, 346 KB]
Download the Operator statement of compliance with the maintenance requirements of NZS 5451: 1989 form [PDF, 86 KB]
This form is used by a heavy vehicle operator to confirm a vehicle’s skid plate structural condition is within safe tolerances.
Heavy vehicle driveshafts and their components, especially the universal joints, need appropriate maintenance, otherwise their life will be shortened dramatically, and they may fail prematurely. Operators, drivers and mechanics, as well as engineers, certifiers and vehicle inspectors, all need to take appropriate action to avoid these potentially dangerous failures.
engage and disengage the clutch smoothly and gradually, especially when starting or changing gear under heavy load, eg when driving uphill
avoid abrupt use of the clutch, as this places higher loads on the driveline, which may cause damage to the driveshaft, or in extreme cases, may lead to immediate driveshaft failure
be alert to any unusual vibration (eg on the gearshifting lever) that may indicate a problem with the driveshaft. Other signs include knocking sounds when starting the vehicle, and/or during gear changes. If vibration or knocking increases, the driveshaft may be about to fail – you must immediately slow down, stop the vehicle, and check the driveshaft.
If driveshaft failure occurs at high vehicle speed, the risk of harming other road users increases significantly.
Operators should ensure:
that driveshafts are maintained and checked regularly
that this maintenance work is carried out according to the manufacturer's written instructions. Industry experience has indicated that, in some cases, you need to lubricate and check driveshafts more frequently than specified by the manufacturer.
Maintenance workshops and mechanics
Maintenance workshops and mechanics should:
- check and maintain the driveshaft according to the manufacturer's instructions. The instructions are likely to include the following directions:
- 'purge-lubricate' with specified lubricant: greasing must be continued until the fresh lubricant is discharged from all outlets of the lubricated component
- ensure that the pressure is not too high as excessive pressure can damage or blow out the seals of universal joints, which in turn will lead to reduced component life
- check the condition (damage, wear, deterioration, excessive play) of all components
- check that all bolts and nuts are present and properly tightened
- check that the bearing cups of the universal joints are correctly positioned, secure, and not able to rotate.
Workshops and mechanics that repair driveshafts or carry out repairs where the driveshaft is partially or fully removed from the vehicle must follow the manufacturer's repair instructions. Instructions are likely to include the following directions:
Thoroughly clean components that are allowed to be re-used. Inspect (replacing if necessary) and lubricate these before re-assembly. Components that are required to be replaced once disassembled must be replaced even if they appear to be in good condition. These components may include bolts, nuts, locking tabs, the straps of universal joints, etc.
Phase the universal joints as prescribed by the manufacturer.
Properly tighten all bolts and nuts.
Use locking devices as specified by the manufacturer.
Heavy vehicle specialist certifiers should ensure that the requirements, which are in force in respect of driveshaft modifications, are complied with.
Read more about modifying a heavy vehicle.
By vehicle inspectors
Certificate of fitness (CoF) inspections include detailed inspection requirements for driveshafts. CoF inspectors should check the condition of driveshafts and their components according to the updated requirements.
Wheels on heavy vehicles need to be properly fitted and maintained otherwise there is a high risk of wheel loss or wheel insecurity – which could lead to a serious crash.
A wheel is subject to a number of forces which act to loosen the wheel nuts.
If one of the wheel nuts loosens then these forces are distributed over the remaining nuts, which can cause the adjacent nuts to loosen as well. As more nuts become loose the process accelerates as the overall clamping force holding the wheel in place decreases.
When the clamping force reduces sufficiently the wheel will move on the hub. This results in side loading and further loosens the remaining nuts, which, if not spotted in time, leads to elongated stud holes, fatigue failure of studs, fretting cracks and in many cases wheel loss.
Loose wheel nuts can occur due to a number of reasons, including: under-torquing, over-torquing, incompatible parts, poor mating surface condition and through not following the manufacturer’s instructions.
- Equipment used to fit wheels needs to be appropriate for the task and in a serviceable condition.
- Torque wrenches should be maintained and calibrated on a regular basis.
- ensure drivers inspect tyres and wheels during pre-trip walk around inspections
- ensure that after a wheel has been fitted the wheel nuts are rechecked for correct torque after a short period of in-service running
- ensure that wheel nuts are checked for security and tightened
- establish causes of wear and damage on loose nuts before re-tightening
- ensure that manufacturer’s written instructions are followed by correctly trained persons and that comprehensive maintenance records are kept
- consider fitting loose wheel nut indicators.
Maintenance workshops and mechanics
Maintenance workshops and mechanics should:
- establish causes of wear and damage on loose nuts before retightening
- ensure removal and fitting of wheels are carried out to manufacturer’s instructions
- ensure all hub/drum and wheel mating surfaces are clean and allow a flush fit with the mounting surfaces of the wheel
- use the correct tightening sequence (wheel nut tightening procedures can vary for different types of wheels with different types of wheel nuts)
- ensure nuts run freely over the whole length of the stud thread by hand
- use a calibrated torque wrench for the final tightening
- ensure that the wheel nuts are re-torqued after a short period of in-service running (between 50 to 100 kms is commonly recommended)
- simply retighten nuts to the recommended torque when re-torquing (do not slacken and re-tighten)
- ensure that manufacturer’s written instructions are followed by correctly trained persons and that comprehensive maintenance records are kept.
Heavy vehicle specialist certifiers should ensure that the requirements, which are in force in respect of wheel modifications, are complied with and that the operator has the relevant technical information.
Certificate of fitness (CoF) inspections include inspection requirements for wheels and wheel nuts. CoF inspectors should check the condition and security of wheels and wheel nuts and their associated components according to the requirements.