Toyota RZ (2RZ / 3RZ)

Toyota's truck four — 2.4 as the 2RZ-FE and 2.7 as the 3RZ-FE — in the Tacoma, 4Runner, T100 and Hilux. An engine with a reputation for outlasting the vehicle around it, which changes what a fault means: a running RZ is very rarely worn out.

Its one era-specific problem is the head gasket on earlier 3RZ engines, addressed by a revised gasket and a service campaign in some markets. The symptom is the ordinary one — coolant loss, overheating, and eventually combustion gases in the cooling system — and on a truck this old the question is whether it has already been done rather than whether it will happen.

The exhaust manifold cracks, presenting as a tick that is loudest cold and fades as the metal expands, and is very often diagnosed as a valvetrain noise.

Beyond those it is chain-driven and unstressed. The timing chain guides wear at very high mileage, and the crankcase ventilation blocks and pushes oil past the seals — the same two items that arrive on every engine of this age.