Clean the engine compartment and exterior surfaces of the power unit using one of a wide range of specialty solvents. This treatment will prevent dirt from getting inside the engine.
If necessary, depending on the nature of the work ahead, the hood can be removed in order to provide freedom of access to the components to be serviced (see chapter Body). Cover the fenders of the car with special covers, or just old blankets to avoid accidental damage to the paintwork.
If there is a suspicion of loss of vacuum or leakage of oil, coolant, exhaust gases, etc. indicates the need to replace the appropriate gaskets or seals, almost any of the listed procedures can be performed without removing the engine from the vehicle (in situ). The foregoing concerns the procedures for replacing the gaskets of the intake pipe and exhaust manifold, the oil pan, cylinder heads, as well as both crankshaft oil seals.
Dismantling, repair and installation of such external components and attachments as inlet pipeline, exhaust manifold, oil pan, water pump (see chapter Cooling, heating systems), starter, alternator, ignition distributor (see chapter Engine electrical equipment) and components of the power system (see chapter Power and exhaust systems) can also be produced in situ.
Since the cylinder heads can be removed from the engine without first removing the power unit, valve train repairs can also be done on the vehicle. In addition, camshafts, timing belt and timing gears are usually replaced in situ.
In an emergency without dismantling the power unit, it is also possible to repair and replace piston rings, pistons, connecting rods and crankshaft connecting rod bearings. However, this opportunity should not be abused due to the difficulties associated with the need to maintain cleanliness and carry out a number of preparatory procedures.