Holden Problems

It sounds like an electrical problem, but being intermittent it can be hard to trace, as you have discovered. I would be checking the crank angle sensor and its connections.

It doesn't seem to be a major problem, so it could be that it needs a tune-up. Perhaps fit new spark plugs, clean the throttle body and the injectors.

You need to get it fixed because the car would be deemed unroadworthy with a park brake malfunction, but I doubt that Holden would cover it under warranty, as brakes are not generally covered.
 

That she got 80,000 km out of a set of rotors is good going, so I wouldn't be concerned that they needed replacing. If you wanted to check that they were actually replaced you could measure the thickness and compare it to a new rotor. As for who pays, it depends on how long it has been since the service. If it's only recent then you stand a chance of having the dealer pay, if you've let it slide for a while before reporting it there's no chance the dealer will cover it.

$1000 does sound like a lot of money to fix an oil leak; I reckon a local mechanic could do it for less. The cost aside I would accept the deal, the car is out of warranty and an oil leak is not something I would spend time and energy fighting over.

As can be seen Holden has told us that the vehicle was correct to specification when it was sold to the customer and that there were issues that would compromise its roadworthiness at that time. As a result the issue remains one between the owner, Bob Webb, and the Victorian Police. A possible course of action would be for Bob to consult a Vicroads approved engineer for an assessment of the vehicle in its current condition.

You certainly shouldn't need to recondition the cylinder head after such a short time. I would be checking for reasons the valves might be sticking. As the fuel injectors gave trouble shortly afterwards I would be looking to the fuel side of the engine. First, I would change fuel brands, definitely not use E10, perhaps use a higher-octane fuel, and regularly run fuel system cleaner through the car.

You don't normally see a water pump leak until you remove the timing belt cover, which is normally done when changing the camshaft timing belt. You don't say what work the dealer was carrying out, but perhaps the leak was discovered in the course of that work. That it was changed in 2009, almost four years ago, has no bearing on the issue, it may well be leaking again.

Get it checked to make sure it is a sensor and not a problem with the airbags. It would be horrible to find out the hard way that there was a problem with the airbags. Before you can start claiming against Holden you need to establish what the problem is. Perhaps it is something that Holden should fix, but you won't know until you find out what's actually wrong.

It is unusual that the airbag required replacing so soon, but the car is going on for eight years old and, as Holden said, the warranty expired some time ago. Where it was serviced wouldn't have had any influence on the failure, what Holden was telling you was that because you hadn't had it serviced at one of their dealers they would not consider a goodwill payment.