Washing the engine with water jet under pressure, for the newer generations of engines, can do more damage than benefit. The reason for this is that they are more sensitive, more precise electronic systems, which must be very carefully treated.
Every modern vehicle has an electronic injection system and ignition system, and in the engine compartment can be accommodated several computers for monitoring certain functions. These systems are highly sensitive and do not tolerate moisture, oxidation, or any detergents for washing the engine.
Why washing the engine of the older generation can be without any problem? Because those engines have very little electricity and they are without electronics. After washing the engine, only compressible air should be used for drying, and then the engine will start again without a problem.
We advise that the modern engines can be washed only if it’s necessary and with a great care. The use of running water under pressure is not recommended. It is necessary to use anti-corrosive agents in a liquid or spray, and to keep an eye on the sensitive electronics and certain clutches such as some connectors, sensors, and, if necessary, some of them need to be protected. The procedure of washing the engine should be made gradually, part by part. After the treatment with the anti-corrosive agents, to dry the surface should be used compressed air or a clean and dry cloth.