Unlike some newer cars which use an electrically-operated park brake, this model Isuzu has a conventional, mechanical park brake set-up. So that’s a good start as the mechanical version is much simpler.

The tiny switch that is operated by the park brake lever (and lights up the warning light) can often fail or short-circuit, leaving the car thinking that the park brake is still applied even though it’s not. But if you’ve gone to the trouble of changing the wiring to the park brake lever, then presumably this switch was replaced, too. Or at least checked.

So the next thing to do is to make sure that the park brake is, indeed, releasing completely when you lower the park brake lever inside the cabin. If the park brake is poorly adjusted, you might find it’s not releasing all the way, and that’s what’s causing the problem. A quick squirt of contact cleaner on the switch would be your first move, however.

This sounds like a case of low transmission fluid. Check the transmission dipstick according to the instructions in the owner's manual to see if the level is where it should be. Low fluid level can cause all sort of problems from slipping to a lack of drive to uneven shifts and shifts occurring when they shouldn't. Also, try to find out what fluid was put in the transmission when it was last serviced. The wrong type or grade of fluid can cause the same types of problems as not enough fluid.

If the fluid checks out, then you need to start looking at other causes such as glitches in the on-board computer that controls the driveline. An electronic scan of the vehicle would be the next step.

Blown turbochargers are hardly an unknown problem on the MU-X or many of the other popular modern turbo-diesel engines that work pretty hard and make lots of horsepower and torque for their capacity.

Some owners report a rattling, metallic noise such as yours; others reckon the sound of a dying turbocharger is more like an air-raid siren. Either way, the turbo needs to be changed sooner rather than later, to avoid the chance of bits of broken turbo being sucked through the rest of the engine with catastrophic results.