Holden Reviews

If your diagnosis is correct, the problem will be with the either sensor that detects the temperature of the coolant, the computer that creates the signal to open, the wiring that carries the message or the thermostat itself. An auto electrician should be able to sort this out by testing the components one by one until the dud one reveals itself.

But there’s another possibility in cars like this one with a thermostat that lives in a plastic housing. Over time and repeated heat cycles, the plastic can degrade and fail internally. At that point, the actual thermostat mechanism can move sideways and jam against the housing, effectively preventing it from opening., At that point the engine can overheat. Don’t rule that out until the condition of the housing has been checked.

A common cause of overheating can be a failed head gasket which allows the coolant to be consumed by the engine. When this happens, soon there’s not enough coolant remaining to cool the engine and the car overheats.

But it may not be as serious as that. You could simply have a stuck thermostat. This is the component that prevents coolant flowing around the engine when it’s first started, forcing the engine to warm up faster. Then, as the engine gets warmer, the thermostat starts to open to allow the coolant to flow through the engine and do its job, maintaining the correct running temperature in the process.

Other possible causes for overheating include incorrect ignition timing, a slipping fan belt, non-functioning cooling fans, a collapsed radiator hose, blocked radiator, a worn water pump and many others. A good mechanic should be able to make a diagnosis and tackle the problem from there.

You could have an engine problem that is causing the vehicle to lose power. The cause of this could literally be a thousand different things. An electronic scan of the vehicle might shed some light on the root cause of the problem, and most mechanics would carry out such a scan before doing anything else.

If the engine is not at fault, you might find the problem can be traced to a transmission that is not shifting gear properly or is slipping, or perhaps even something as simple as a dragging brake or poorly adjusted park-brake. But before you hit the workshop, you can check simple things like the condition of the engine’s air filter to make sure there’s no obvious cause. If your car is a turbocharged model, check the plastic trunking that carries the boost from the turbo to the engine’s intake. This trunking can split or fall off, leading to a loss of boost pressure and, therefore, performance.