Using an engine diagram to perform intensive repairs on a Honda engine is helpful because it allows the mechanic to label each of the dozens of bolts and small parts removed from the engine and reminds him exactly where each one goes during reassembly. Use Post-It notes or a Sharpie marker to carefully label each part removed from an engine and store them in a careful, organized way during the period of disassembly.
An engine diagram is an essential tool for intensive repairs like transmission swaps, engine swaps, bottom end rebuilds, bent valve, engine mount or head gasket replacements and timing belt replacements. Diagrams are also useful for less involved repairs such as starter, alternator, water pump, power steering pump or accessory belt replacement. Since not all engine diagrams feature torque settings and step-by-step instructions, have your vehicle's maintenance guide available for reference when attempting any of these tasks.
If performing an intensive repair that involves removing the engine, transmission or cylinder head from the vehicle, an engine diagram may not be the only diagram needed. A vacuum hose diagram, cooling system diagram and wiring diagram may be useful for the mechanic to remember where each hose and electrical connector attaches to the drivetrain. Diagrams with hundreds of parts labeled on them often appear so busy and disorganized that identifying specific parts and the lines that lead to their mounting locations on the engine is difficult.