I don't remember if i mention it before but when i said to the mechanic to remove the reservoir and clean it with a spray and then use compressed air or a clean rag to clean it inside said immediately ''NO''.

I was against of use of any chemical way, i asked why and he insisted that there is a possibility to remain something and this will make a chemical reaction with the Hydraulic Oil and soon or later i will have a problem with the seals.

He preferred the ''flush with new oil" method.

I can understand his point  but it depends on what you use to clean the reservoir and that would be his worry, what you use, but as I put before if you just use lint-free cloths and fresh oil to clean the inside it will not be sparkling but it will be cleaner and no risk of any other chemical other than your PS fluid of choice.  For cleaning the outside, which would be done separately so as not to contaminate the inside, anything that will not damage the reservoir material. 

 

With cleaning to do a good job you need to be methodical and thorough, if you cannot use the chemicals to do the hard work then you have to do the hard work yourself.  Many are too, lazy, arrogant, macho, ego to do a good job of cleaning as they see the work as beneath them, owners and mechanics yet if you see a good tradesperson that is where they put in a lot of time and effort.