When it comes to washing the engine compartment with steam, its supporters point out that its jet, unlike the jet of water from the Karcher, cannot damage anything under the hood. Let’s start with the fact that a normal motor does not need a sink in principle. It works great both in a dusty form and shining with perfect cleanliness.
Steam is the same water, only in a different state of aggregation. Condensing on the surfaces of the engine compartment, it, as in the case of washing with the usual jet of water, can penetrate into insufficiently sealed electrical connections. Which leads, for example, to problems when starting and running the engine, electrical “glitches” and similar possible consequences of washing the engine in any way.
Superheated steam, unlike water, also affects all kinds of plastic and rubber under the hood with its high temperature. Because of it, for example, the plastic insulation of the elements of the same electrics may be broken. And then the condensate will complete the dirty work started by overheating. In rubber products, elevated temperatures can cause accelerated “aging”. Do you need all this? If not, it is better not to wash the motor with steam.
But if you really feel like doing cleanliness, then do it with the help of good old chemistry and a gentle jet of water – preheating the engine and then giving the engine compartment at least an hour to dry completely.