In the case of the ZD30T engine and turbo failures in Patrols, the ineffective control of boost pressure, non-effective intercooling, exhaust gas entering the inlet manifold and combustion process, non-existent overboost protection, and high exhaust manifold back pressure all combine to create piston crown overheating failure and extreme turbo shaft speed, creating bearing failure in the turbocharger. With the turbo compressor and shaft failure with shrapnel damage to the engine internals, problems in the ZD30T Navaras, a substandard and failure-prone, poor-quality original turbocharger, are the prime cause of repeat failures from as low as 60,000km.