After a major service including a replacement water pump at a cost of $2000, we travelled less than 195 km over several weeks in our 2007 Toyota Prado and our motor/radiator blew up, melting the tappet cover and suffering major damage throughout. An independent report states: "There is severe damage to the engine as a result of being severely overheated. The cylinder head is soft, unrecoverable and requires replacement. The plastic on the tappet cover has been melted over the camshaft. The engine is not sludged-up at all and all of the bearings float with no bearing damage. If there were anything on the pick-up, it would be from the pistons melting. There is no evidence whatsoever of any oil starvation, as suggested".
The Servicing Mechanic (not a Toyota Mechanic) stated: "Unfortunately your Independent report did not have an explanation as to why there was no oil in or on the cylinder head, why the tappet cover had melted, as it is not part of the cooling system, and was only damaged at the rear of the fuel rail. Furthermore, as to why pressure test showed no leaks, the temperature gauge did not rise and severe noise and lack of engine performance was not noticed. In our knowledge and experience, if there were an air lock in the cooling system your vehicle could not have travelled 195 km with or without towing your van as stated. Severe overheating would be evident in damage to the radiator, header tank, radiator cap and or coolant hoses, with little or no fluid left in system. No damage or failures were found in this area. We recommend further testing be carried out on fuel, oil pump and aftermarket performance chip fitted to your vehicle".
Looks like we will be footing the bill for a reconditioned or new motor and no one can give us an exact costing until they start pulling the vehicle apart. We are going around in circles. We are told a motor would range from $6000 (reconditioned) to $12,000 (new) and the price could escalate depending on what other damage there is when they do the job. As we are not mechanics and can only state that other than the air-conditioner stopping and the vehicle losing power, we managed to pull to side of the road and stop. Next thing severe steam escaped and vehicle was no longer drivable. On no occasion did we hear any knocking or noise coming from the motor. What would be the advantages/disadvantaged of putting a reconditioned motor in versus a new motor? Where do people go to get assistance on this type of problem, we keep getting conflicting information?
I doubt that your engine had a problem with the cooling system; it sounds like a major meltdown, perhaps due to oil starvation, or a problem with the fuel system that has caused it to severely lean out and damage the pistons. I would suspect it's the latter. Whatever has caused the problem you are up for a new engine, and I would go for a new one over a reconditioned one. While it's more expensive your car has only done 118,000 km so it's still relatively new. I would suggest you remove the aftermarket computer chip and return the computer to factory stock. The chip could well be the cause of your problem. As for assistance you can only consult mechanics, in this case I would consult one that's experienced in Toyotas and Prados.