Ive heard that brake components will corrode and fail if stored too long (couple years or so). This is in reference to a used ABS pump and master cylinder.

The master cylinder actually pitted up pretty good on the outside while left in a plastic bag for less than a year (it was wiped down but not cleaned/flushed before putting away).

Should the cylinders be cleaned out so there is no residual brake fluid? Or fill them with an oil, brake fluid, or other product to keep them from corroding internally when not used?

 

Drain what oil you can get out. The key here is to plug the holes. Thats why you see caps in them when you buy new or rebuilds. All brake fluids absorb water out of the air .This is what does the damage and the reason you should change your brake fluid at least every 1 1/2 yrs. Then just put them in a sealed plastic bag to keep the rust or oxidation to a minimum. There is nothing that will stop the rubber in them from rotting (aging and become brittle ) in due time though.That is why there are special fluids for your brake system which are easier on the systems rubber components.

 

Some parts stores carry brake component lube, I'm talking about the stuff used for rebuilds. I'm not sure what it offers for corrosion resistance, but I'd look at the bottle and see. I know Savage KOI hasit here locally, I'd check NAPA.