Toyota HiLux Pricing and Specs

Air-conditioning can really add another layer of stress to an engine. Since the air-con compressor is driven off the engine (via a belt) it's just another thing for the engine to deal with. And since the engine has to make more power to run the air-con and travel at the same speed, it uses more fuel. And more fuel burned equals more heat, it's pretty basic physics to that point.

Any vehicle with a cooling system that is already a bit marginal can easily be made to overheat by switching on the air-conditioning. So the first thing to do is make sure there are no leaks in the cooling system, the radiator is not clogged internally or covered externally in dead bugs, the radiator hoses are not collapsing when you rev the engine, the water pump is working efficiently and the radiator cap is holding pressure (the boiling point of the coolant rises as you pressurise the system. Again, basic physics: Water boils at 100 degrees-C at sea level, but at the summit of Mount Everest, if you set up your camping stove, you'd boil water at just 68 degrees-C due to the lower atmospheric pressure).

The other thing to check is the condition of the cooling fans. The engine will have its own fan, but cars with air-conditioning usually have a second cooling fan that starts up when the air-con is switched on. You can tell if this second fan starts up by listening for it when you hit the A/C switch. If it isn't coming on (or the engine's fan is broken, slipping or doesn't have the correct shroud fitted) than this can easily lead to overheating.

It sounds like the needle has physically moved on its shaft to exhibit this problem. The question is how. Did you hit a huge pothole or bump off-road? Has any part of the dashboard been adjusted or pulled apart for another reason? Has the vehicle been operated in really dusty conditions (sufficient to have jammed up the smooth movement of the speedo needle)?

Unlike older vehicles, the modern HiLux doesn’t use a simple mechanical cable to power the speedo. Instead, it uses a vehicle speed sensor as part of the transmission to inform the body computer of the vehicle’s speed which then transfers an electrical signal to the speedo in the dashboard. If anything goes wrong with that chain of electronic command, then the speedo can be affected.

The fines are a separate matter as to what you eventually do with the vehicle. They need to be paid, regardless of what else you decide to do.

As you say, you can return the vehicle to standard condition or have it engineered for the modifications you want and then have the defects cleared by having the car inspected. But if you decide to sell the vehicle, it can't be sold with current defects and while still registered. You can clear the defects and sell the vehicle with registration, or cancel the registration and then sell the car. In any case, there's no way you could obtain a roadworthy certificate with the defects you've listed so the simplest way to get rid of the car would be to cancel the registration and then sell the car.