I just had my car professionally detailed. Before they cleaned the engine, they sprayed WD40 on all the electrics to keep the water out. Anybody ever heard of this technique? Seems a lot easier than wrapping them in plastic.

 

These are the precautions I take before starting an engine compartment detailing-
•Remove any excess debris, leaves and etc from the hood, grille or air-vent openings
•Spray all electrical connectors with WD40, which repels moisture / water.
•Use cling-film or Saran wrap elastic covers to cover any sensors, electrical black boxes, electrical devises that could cause an electrical short-circuits if subjected to water spray.
•This will not guarantee that you won’t cause a problem when cleaning an engine bay but it will greatly reduce the risks.
•Start and run the engine to get it warm, not hot, this will enable the de-greaser to work more efficiently on a warm surface.
JonM

 

WD40 does act as a water displacer, but it probably also conducts electricity. Would this make it possible for something to short?

 

I prefer to spray a towel and do a damp wipe down after the dry debris are removed via vacuum. Then dress the engine bay accordingly.