VT VX VY VZ Commodore Repair Manual
The VZ is the last of the VT series. As there have been 3 previous models to work out the bugs, a VZ is generally considered a pretty safe bet. It did introduce the Alloytec engine which may be problematic for some. There is also no series 2.
An OBD2 scanner is a great way to correctly diagnose issues and faults in newer model cars (mid 90’s onwards).
The VZ Commodore was the last evolution of the long-running VT-to-VZ platform and, in many ways, Holden had finally ironed out years of bugs and refinement issues by the time the VZ arrived in 2004. It drove better, looked sharper, and introduced the new Alloytec V6 alongside the now-legendary LS1 and LS2 V8s.
But no Commodore survives 20 years without developing a few weak spots.
Some VZ problems are minor annoyances. Others — especially on neglected cars — can become wallet destroyers if ignored for too long.
Here are the most common VZ Commodore problems owners and buyers should know about.
1. Timing Chain Problems (Alloytec V6)
If there’s one issue that defines the VZ Commodore, it’s timing chain trouble.
The Alloytec V6 was a huge step forward from the old Ecotec in terms of power and refinement, but early engines quickly earned a reputation for stretched timing chains — especially in poorly serviced cars.
The problem became so widespread that timing chain discussions are now practically part of VZ ownership culture.
Common symptoms
- Check engine light
- Rattling on startup
- Rough idle
- Poor fuel economy
- Reduced performance
- Fault codes relating to cam timing
The biggest killer is neglected oil changes. Dirty oil and long service intervals accelerate chain wear dramatically.
Many buyers specifically look for evidence the timing chains have already been replaced.
Related guide
- VZ Commodore Timing Chain Problems
- Best Oils for Alloytec Engines
- VZ Timing Chain Replacement Cost Guide
2. Automatic Transmission Problems
The VZ’s automatic transmissions are generally decent units, but high-kilometre cars can develop problems if they’ve been neglected.
Many VZs spent their lives as commuter cars, taxis or fleet vehicles, and plenty never received proper transmission servicing.
Heat and old fluid are the biggest enemies here.
Common symptoms
- Slipping gears
- Delayed shifting
- Harsh gear changes
- Transmission shudder
- Fluid leaks
Tow cars and modified V8 models tend to wear transmissions faster, especially if the original cooling setup remains untouched.
A healthy transmission should shift smoothly and predictably.
Related guide
- Best Transmission Fluids for VY, VZ Commodore
- VY, VZ Auto Transmission Service Guide
3. Cooling System Failures
Cooling system issues are extremely common on ageing VZ Commodores.
By now, most VZs are well over 15 years old, and many original plastic cooling components are becoming brittle and failing from age and heat cycling.
Radiators, thermostat housings and heater hoses are all known problem areas.
Common symptoms
- Coolant leaks
- Overheating
- Low coolant warnings
- Temperature fluctuations
- Sweet coolant smell
Overheating an Alloytec engine is never good news and can quickly lead to expensive repairs.
Preventative cooling system maintenance is one of the smartest things a VZ owner can do.
Related guide
- VY, VZ Commodore Cooling System Problems
- Best Coolants for Holden Commodores
4. Differential Whine
A whining diff is almost a rite of passage in older Commodores.
VZ Commodores — particularly SS and SV8 models — can develop differential noise as kilometres pile on. Hard launches, burnouts and aggressive driving only speed things up.
Some cars develop mild noise for years without major failure. Others get progressively louder over time.
Common symptoms
- Whining during acceleration
- Clunking noises
- Vibrations at speed
- Diff oil leaks
Ignoring low differential oil levels can quickly turn a minor problem into a major rebuild.
Related guide
- VY, VZ Commodore Differential Problems
- Best LSD Upgrades for VY, VZ Commodore
5. Interior Wear & Roof Lining Sag
The VZ interior has actually held up fairly well compared to some earlier Holdens, but age is now catching up with these cars.
One of the most common complaints is sagging roof lining — especially in cars exposed to harsh Australian heat for years.
Other common interior issues include:
- worn seat bolsters
- peeling trim
- broken window switches
- faded plastics
- rattles and squeaks
The good news is that aftermarket interior parts remain widely available.
Common symptoms
- Roof fabric sagging
- Interior rattles
- Cracked trim pieces
- Loose door cards
A tidy interior can massively improve how a VZ feels overall.
Related guide
- VT, VX, VY, VZ Commodore Interior Restoration Guide
- Best Interior Cleaning Products for Holden Vehicles
6. Power Steering Leaks
Power steering leaks are another very common VZ issue.
Hoses, pumps and rack seals all become vulnerable with age, especially on higher kilometre cars.
Many owners first notice the problem after finding fluid spots on the driveway.
Common symptoms
- Whining steering pump
- Heavy steering
- Fluid leaks
- Groaning noises while turning
Ignoring low power steering fluid levels can damage the pump quickly.
Related guide
- VY, VZ Commodore Power Steering Problems
- VY, VZ Steering Rack Leak Guide
- Best Power Steering Fluids for Holden Vehicles
7. Electrical Gremlins
Like many early-2000s cars, the VZ can develop annoying electrical faults as it ages.
Nothing catastrophic most of the time — just the sort of little gremlins that slowly creep into older Holdens.
Common issues include:
- faulty window regulators
- central locking failures
- BCM faults
- stereo issues
- battery drain problems
Weak batteries can also create strange intermittent faults that seem unrelated.
Common symptoms
- Windows not working
- Flat battery
- Random warning lights
- Remote locking problems
- Interior electronics failing intermittently
Electrical problems can be frustrating to diagnose because symptoms often come and go.
Related guide
- VY, VZ Commodore Electrical Problems
- VZ Battery Drain Guide
- Best Scan Tools for Holden Owners
8. Suspension Wear
The VZ chassis still feels surprisingly good today, but worn suspension can completely ruin the driving experience.
Bushes, sway bar links and shock absorbers are all common wear items on ageing Commodores.
Lowered cars tend to wear components faster again.
Common symptoms
- Clunking noises
- Poor ride quality
- Uneven tyre wear
- Steering vibration
- Loose handling feel
A fresh suspension setup can transform how a VZ drives.
Related guide
- VY, VZ Commodore Suspension Problems
- Best Suspension Upgrades for VY, VZ Commodore
- VY, VZ Lowering Guide
9. Fuel Economy Issues
VZ Commodores were never economy cars, but excessive fuel consumption can indicate underlying problems.
Dirty throttle bodies, worn oxygen sensors and timing chain wear can all affect fuel economy.
Heavy right feet don’t help either — especially in LS-powered cars.
Common symptoms
- Poor fuel economy
- Rough idle
- Hesitation
- Black exhaust smoke
Many VZs respond surprisingly well to a proper service and intake clean.
Related guide
- VZ Commodore Fuel Economy Problems
- Best Spark Plugs for VZ Alloytec Commodore
Is the VZ Commodore Reliable?
Despite the common problems, the VZ is still considered one of the better older Commodores to own. The platform was well sorted by the time Holden released it, and parts availability remains excellent across Australia.
VT VX VY VZ Commodore Repair Manual