Blockages and corrosion are the biggest issues you are likely to face in this application. This usually only occurs through corrosion of pipework, irregular servicing (cooling fluid change) and not changing any filters designed to remove particulates.
The absence of salts works in different ways depending on the application. E.g. prevents furring of cooling pipework.
pH can also be an issue – Aluminium is affected by a high pH and other metals are affected by a low pH.